Process for electro-codepositing inorganic particles and a metal on a surface
This invention relates to a process for depositing composite coatings containing a metal and inorganic particles from an electroplating bath. More specifically, the invention relates to a process for the codeposition from an electroplating bath of a metal and solid inorganic particles on an article acting as a cathode and to the resulting coated article. 
     One process of the general type indicated above is described in U.S. Pat. No. 3,891,542. In accordance with the disclosed process, nickel and silicon carbide particles are codeposited electrolytically from an aqueous bath on an article which serves as the cathode. The silicon carbide particles are kept suspended in the bath with the aid of a surfactant such as sodium lauryl sulphate. One disadvantage of the disclosed process is that only a low percentage of particles can be incorporated into the composite layers. A weight percentage of silicon carbide particles of 3 to 5% is disclosed. However, this percentage can only be obtained at a relatively high concentration (90 to 150 grams per liter) of silicon carbide particles in the bath liquid. Other required undesirable conditions are an exceptionally high electrolyte concentration and very vigorous agitation of the bath liquid to retard sedimentation of the suspension and to obtain a sufficiently homogeneous distribution of the particles in the coating. 
     It is an object of this invention to provide an improved process for the simultaneous electrolytic deposition of a metal and solid inorganic particles such as silicon carbide on a surface of an article acting as a cathode. Another object of the invention is to provide such an electrolytic deposition process which makes it possible to incorporate a larger percentage of the inorganic particles in the resulting coating. Still another object of the invention is to provide improved dispersion of the inorganic particles in the electroplating bath without requiring vigorous agitation. 
     The present invention provides a process which makes it possible to incorporate substantially higher percentages of solid particles in metal coatings with the use of an electroplating bath having a substantially lower concentration of solid particles and electrolyte without vigorous agitation of the bath. 
     In accordance with the invention, an electroplating bath is provided which contains a surfactant in the form of a cationic fluorocarbon compound in at least the same weight ratio of surfactant to particles in the bath liquid required in an 0.005 N KNO 3  -solution for the particles to assume a zeta-potential of at least +40 mV with the exclusive use of said cationic fluorocarbon compound as the surfactant. 
     It should be added that the use of a cationic compound for the codeposition from an electroplating bath of a metal and solid inorganic particles on an object which acts as a cathode has been proposed before in the U.S. Pat. No. 3,844,910. An amino-organosilicon compound, for instance gamma-propyltriethoxysilane, is employed in the disclosed bath to promote the incorporation of non-metallic particles such as silicon carbide in a matrix of metal. Although the results obtained with the process are better than those of the previous processes, the percentage of particles incorporated is still insufficient for many purposes. 
     Moreover, in the case of a particle size of over 10 microns, the amount of nonmetallic particles that can be incorporated by the disclosed process has been found to decrease with increasing average particle size. 
     The use of a cationic surfactant in the incorporation of solid inorganic particles in a matrix of metal also is disclosed in British Patent Specification No. 1,070,343. The amount of cationic surfactant employed, viz. cetyltrimethylammonium bromide, is only 10 mg per 25 grams of particles and is insufficient to cause the particles to assume a zeta-potential of at least +40 mV in an 0.005 N KNO 3  -solution. Moreover, the disclosed surfactant is of the hydrocarbon type, which has a very unfavorable influence on the quality of the electrodeposited coating (ductility). 
     In the Japanese Patent Specification No. 50-45735, a surfactant of the fluorocarbon type is used in the codeposition from an electroplating bath of gold and abrasion-resistant nonmetallic particles on an article acting as cathode. In the example given in this patent, the incorporation of titanium nitride (TiN) in a coating is carried out with the use of 3 g of surfactant of the fluorocarbon type per 20 g of particles. Hence, the particles used are very small, viz. 0.05 μm, the specific surface area is very large and such a small amount of surfactant will not be sufficient to obtain a zeta-potential in an 0.005 KNO 3  -solution of at least +40 mV. Moreover, nothing is said in this patent about the charge of the fluorocarbon surfactant used in the example. 
     A process is disclosed in U.S. Pat. No. 3,787,294 in which a cationic surfactant of the fluorocarbon type is used in the codeposition from an electroplating bath of a metal and graphite fluoride particles on an article acting as cathode. It is generally known, however, that graphite fluoride particles resemble polyfluorocarbon particles more than they resemble particles whose incorporation forms the subject of the present invention. This U.S. patent can therefore not be considered to contain a general teaching with regard to the incorporation of inorganic solid particles in a metal coating. 
     For the determination of the surface area of the particles use is preferably made of the nitrogen adsorption method of Brunauer, Emmett and Teller (BET), which is standardized in the German Industrial Standard DIN 66132. 
     By solid inorganic particles that can be incorporated in accordance with the process provided by the invention are to be understood here not only all particles that are of solid inorganic compounds which are inert relative to the bath conditions, such as the carbides, borides, silicides or nitrides of titanium, zirconium, wolfram, hafnium, niobium, tantalum, chromium, molybdenum, vanadium, and thorium, but also particles of simple or composite metal oxides such as Al 2  O 3  ; SiO 2  ; IrO 2  ; Cr 2  O 3  ; ZrO 2  ; PbO 2  ; Pb 3  O 4  ; Al 2  O 3 .2TiO 2  ; Beo.Sio 2  and ZrO 2  Si and the like. To obtain an abrasion-resistant coating, the incorporation of SiC or B 4  C particles are preferred. Also, particles of metals or metal alloys can be included in composite metal coatings in accordance with the invention. Also, graphite, sulphur, silicon, diamond, sulphides (such as molybdenum disulphide) and silicates (talc, mica) can be codeposited with a metal in accordance with the invention. 
     The percentage of inorganic particles that may form a part of composite coatings when use is made of the process provided by the invention varies from a few percent say about 3% to the theoretically maximum volume percentage of about 70%. It has been found that the smaller the particles the more of them can be deposited from the same amount by weight per liter of bath liquid. 
     The process of the invention can be used for depositing the same metals as those which can be deposited from an electroplating bath by the prior art processes. As examples of these metals may be mentioned silver, iron, lead, nickel, cobalt, cadmium, copper, zinc and metallic alloys such as bronze, brass and the like. 
     In addition to solid inorganic particles, the electroplating baths used in the process according to the invention may contain particles of some other inorganic or organic material. As an example, a combination of SiC, MoS 2  and Pb-oxide+PTFE* may be codeposited. Of particular importance are resinous particles of, inter alia, polyfluorocarbon compounds, polyvinyl chloride, polyvinylidene chloride, polyolefins, polyesters, polystyrene, polyacrylates, polyamides, polyimides, aromatic polyamides and polyurethanes. If use is made of such combination of different particles it is advisable as much as possible to choose the same particle size. 
    
     The preparation of the dispersions to be employed in the present process may be carried out in any convenient manner. It may be effected by adding the calculated amount of cationic surfactant to the electroplating bath in which the envisaged particles have been taken up or, as is preferred, first adding the wetting agent to a very strongly agitated, concentrated suspension of the particles to be occluded and subsequently adding the resulting suspension to the electroplating bath. 
     Particularly in the simultaneous incorporation of resinous particles, it is very much advisable that the various dispersions should be prepared separately prior to their being added to the electroplating bath. 
     In the process according to the invention, use should be made of cationic surface active fluorocarbon compounds such as those having one of the following structural formulae: ##STR2## 
     Of the above compounds, the last-mentioned one is to be preferred because it is a surfactant that gives the most favorable results. In view of the possibility of electrochemical oxidation and precipitation, it is preferred that the anion of the lastmentioned compound be replaced with a Cl -  or SO 4   2-  ion. 
     Under some circumstances, it may be desirable for the electroplating bath also to contain a stress reducing agent, such as p-toluenesulphonamide or saccharin. 
     The invention will be further described in the following examples, which are all directed to the codeposition from an electroplating bath of a metal and solid inorganic particles of various chemical compositions and particle sizes. First of all, a description will be given of the general conditions used in the examples, after which the results of the experiments will be summarized in a number of tables. 
     The experiments, according to the process of the invention, were carried out with the use of a cationic fluorocarbon-containing surfactant. For comparison, experiments also were carried out in the presence of a cationic surfactant not containing a fluorocarbon chain, viz. a surfactant of the hydrocarbon type. 
     Measurement of zeta-potential 
     Preparatory to the experiments, first the zeta-potential of the solid inorganic particles to be incorporated by electrodeposition was measured as a function of the amount of surfactant. This was done in order to determine at what amount of surfactant the particle potential exceeded +40 mV. In the actual experiments in the electrolyte bath, a somewhat larger amount of surfactant was used than the amount thus determined. Moreover, in Example I, experiments were carried out with the same surfactant in two concentrations that were lower than the determined amount. The measurement of the zeta-potential was so carried out that as far as possible, the same concentrations of the solid inorganic particles in the aqueous dispersions were used as those that were to be employed in the electroplating bath. 
     In 350 ml-beakers, a series of dispersions were prepared, one of them consisting of 121/2 grams of solid inorganic particles and 250 ml of demineralized water. The other dispersions of the series contained varying amounts of surfactant as well as 121/2 g of solid inorganic particles and 250 ml of demineralized water. For each of the various kinds of particles, a separate series of dispersions were prepared in this way. By &#34;various kinds of particles&#34; are not only to be understood here particles of different chemical compositions, but also those that only differ in particle size. The contents of the beakers were homogenized for 2 minutes with an Ultra Turrax stirrer, type T 45/N of the German firm of Janke and Kunkel A. G., operating at a speed of 10,000 revolutions per minute. Subsequently, the dispersions were allowed to stand for 15 hours to permit the air to escape. Next, the dispersions were stirred with a magnetic stirrer for about 10 minutes without air occlusion and visually inspected then for stability, flocculation symptoms and sedimentation speed. Subsequently, the dispersions were stirred with the magnetic stirrer for about 5 minutes, after which from each beaker 1 ml of the dispersion was taken, which was diluted with 50 ml of an aqueous 0.05%-solution of KNO 3  (0.005 N KNO 3  -solution). 
     Of the dispersions thus diluted, the velocity of the solid inorganic particles under the influence of an electric field was measured. 
     From this velocity, the electric conductivity of the dispersion and the electric field strength, the zeta-potential was calculated. For further particulars about the measurement of the zeta-potential reference is made to &#34;Electrophoresis&#34;, Duncan J. Shaw, Academic Press, London, New York, 1969. 
    
    
     In the following Example I, the procedure used in the experiments will be further described. The same procedure, mutatis mutandis, is used in all the other examples. Differences, if any between the examples will appear from the respective tables. In these tables are summarized the various conditions used in the experiments and the results obtained with the experiments. 
     EXAMPLE I 
     For the electrolyte bath, use was made of a Watt&#39;s nickel plating bath, the solid inorganic particles of silicon carbide having being supplied by Kempten GmbH, Munich, under the name SiC 1200. They are particles having a mesh value of 1200 and an average size of about 5 μm. 
     A 11/2 liter nickel plating bath was prepared employing the following ingredients: 
     
         ______________________________________                                    
                   grams/liter                                            
______________________________________                                    
NiSo.sub.4 . 6H.sub.2 O                                                   
                     240                                                  
NiCl.sub.2 . 6H.sub.2 O                                                   
                     40                                                   
H.sub.3 BO.sub.3     40                                                   
______________________________________                                    
 
    
     The pH was 4.2 and the temperature was 52° C. 
     To this bath there were added 75 grams of SiC 1200  and 375 mg of a cationic fluorocarbon surfactant, i.e., 5 mg of surfactant per 1 gram of SiC. The surfactant had the following structural formula: ##STR3## 
     In a 200 ml-beaker, this mixture was homogenized with an Ultra Turrax stirrer of the type mentioned before at a speed of 10,000 revolutions per minute. Subsequently, the resulting dispersion was gently stirred for one-half hour at a temperature of 52° C. with an IKA Combimag magnetic stirrer to allow the escape of air occluded in the preceding stirring operation. 
     As could afterwards be established, the dispersion obtained looked moderately stable. 
     As cathode now a round bar of stainless steel 60 mm long and 4 mm in diameter was hung in the bath contained in the beaker. The bar had been pretreated successively by blasting with granular corundum having a mesh value of 220, rinsing, degreasing with an alkaline detergent, rinsing, activating in a boiling solution of FeCl 3  and again rinsing with water. 
     The anode hanging in the beaker consisted of a nickel plate 1 mm thick, 8 cm high, and 15 cm long and was so bent that it was just touching the inside wall of the beaker. The anode and the cathode were then connected to a current source supplying a direct current of 0.75 A. 
     So, considering the cylindrical outer surface area of the cathode, the current density was 10 A/dm 2 . The electrodepositing lasted 15 minutes, the bath being moderately stirred to prevent sedimentation of SiC particles. Next, the cathode and the anode were removed from the beaker, rinsed with water and transferred to a beaker of the same dimensions containing a normal Watt&#39;s nickel plating bath (without SiC or surfactant). In this bath, the cathode bar was subjected to a continued electroplating treatment lasting 30 minutes at a current density of 5 A/dm 2 . As a result, a second coating consisting of nickel was deposited on the composite coating of nickel and silicon carbide formed in the first electroplating step. 
     Of the bar thus treated, a 15 mm long piece was sawed off and entirely embedded in a solidifying mass. Then the integrated whole of embedding mass and bar was ground off until a semi-cylindrical part of the bar was left, the outer nickel coating serving as a supporting layer. On the fine-ground face, the incorporated darker SiC particles could be very well distinguished from the lighter nickel. 
     The uniformity of distribution of the SiC particles in the nickel could, therefore, be very well determined visually. The volume percentage of incorporated SiC particles was determined with a Zeiss microvideomat. The experiment was carried out at three different concentrations of surfactant, based on the amount by weight of SiC particles: 
     a. 5 mg of surfactant per gram of SiC 
     b. 10 mg of surfactant per gram of SiC 
     c. 20 mg of surfactant per gram of SiC 
     The results of the experiment are summarized in Table 1, which also gives the above-mentioned experimental conditions. 
     By the term &#34;zeta-potential without surfactant&#34; used in this table and also in other tables is meant the zeta-potential which was measured with the dispersion which exclusively contained the respective inorganic particles and demineralized water. 
     As is shown by Table 1, the use of 5 and 10 mg of surfactant per gram of particles resulted in incorporating only a small amount of SiC, which moreover was not homogeneously distributed in the nickel. The zeta-potentials in the corresponding 0.005 N KNO 3  -solutions were below +40 mV and were -25 and +12 mV, respectively. It was also found that during the dispersing of the electrolyte, the particles and the surfactant, using 5 and 10 mg of surfactant per gram of SiC, respectively, a flocculent mixture was formed. 
     Both quantitatively and qualitatively the incorporation was considerably better when use was made of 20 mg of surfactant per gram of particles having a zero-potential of +76 mV. The volume percentage of the incorporated SiC particles was 57, and the particles were homogeneously distributed in the nickel. 
     EXAMPLE II 
     The procedure used in Example I was repeated with SiC particles having a size of about 15 μm and supplied by the Dutch firm of Norton at Rotterdam under the name SiC 500. The conditions and the results are given in Table 2. 
     EXAMPLE III 
     In the experiment on which this example is based, the solid inorganic particles were of B 4  C. Particles of this boron carbide having a particle size of about 2 μm, known under the name B 4  C 1500 , had been obtained from the German firm of Kempten GmbH, Munich. 
     Use was made of a nickel sulfamate bath and a different cationic fluorocarbon surfactant from the one used in Examples I and II. The surfactant of this Example II had as the structural formula ##STR4## 
     Further conditions and the results of this experiment are included in Table 3. The table shows that under the given conditions the particles were quite satisfactorily incorporated, both quantitatively and qualitatively, also when use was made of boron carbide. 
     EXAMPLE IV 
     In this example, use was made of solid inorganic MoSi 2  particles supplied by the firm of Starck at West-Berlin. The bath was again a Watt&#39;s nickel plating bath and the surfactant again of the type used in the Examples I and II. Additional data are mentioned in Table 4. Also in this experiment, both a qualitatively and quantitatively satisfactory incorporation of particles was obtained. 
     EXAMPLE V 
     The material of the solid inorganic particles in this experiment was a diamond powder supplied by the Swiss firm of Rudolf Spring A. G. under the name Diamond grade 3. Use was made of a nickel sulfamate bath and the same type of surfactant as employed in Example III. Table 5 gives further particulars about the conditions used in and the results obtained by the experiment. Considering the relatively small concentration of diamond powder (as little as 20 g/liter bath liquid) a remarkably high percentage of incorporated diamond powder was reached (28%) compared with the percentage obtained with the known electroplating process for deposition of metals and diamond powder. 
     EXAMPLE VI 
     In the experiment relating to this example, the solid inorganic substance consisted of chromium powder having a particle size of about 2 μm. The powder had been supplied by the American firm of Alfa Products at Danvers. The experiment was again carried out in a Watt&#39;s nickel plating bath, use being made of the same surfactant as in Example I. The conditions and the results of the experiment are given in Table 6. The composite layer contained 47 percent by volume of chromium powder which was homogeneously distributed in it. When this experiment was carried out in accordance with the procedure described in British Patent Specification No. 1,070,343, using as surfactant n-hexadecyltrimethyl ammonium bromide (CTAB) (a nonfluorocarbon-containing surfactant) the zeta potential was found to have a value not exceeding +20 mV. The particles were not homogeneously distributed over the surface. 
     The resulting coating was black and had a poor appearance. 
     In the following three comparative examples use was made, as in Example I, of a Watt&#39;s nickel plating bath containing dispersed silicon carbide particles referred to as SiC 1200 . However, instead of with a cationic fluorocarbon surfactant, the treatment was carried out in the presence of cationic hydrocarbon surfactants. 
     EXAMPLE VII 
     The cationic hydrocarbon surfactant had the following structural formula: ##STR5## The conditions and results of the experiments are shown in Table 7. 
     EXAMPLE VIII 
     The cationic surfactant used here had the following structural formula: ##STR6## 
     Additional data are mentioned in Table 8. 
     EXAMPLE IX 
     In the experiment carried out according to this example use was made of a cationic surfactant having the structural formula: ##STR7## 
     Table 9 gives additional data on experimental conditions and results. 
     Although in all the comparative Examples VII-IX, the zeta potential can be seen to lie above the set lower limit of +40 mV, the use of a cationic surfactant which is not of the fluorocarbon type results in the incorporation of a considerably smaller amount of SiC than is the case in Example I for a zero-potential of +76 mV (0, 12 and 10 percent by volume in the Examples VII, VIII and IX, respectively, against 57 percent by volume in Example I). 
     EXAMPLE X 
     In the experiment according to this example, use was made of a mixture of two inorganic substances. One substance was SiC 1200 , as employed in Example VIII. The other substance was molybdenum disulphide having a particle size of about 25 μm. It had been obtained from the Swiss firm of Fluka A. G. 
     The experiment was again carried out in a Watt&#39;s nickel plating bath, use being made of the same surfactant as in Example I. In table 10, the conditions used and the results obtained are summarized. The composite layer contained 27 percent by volume of silicon carbide and 18 percent by volume of molybdenum disulphide. Both substances were homogeneously distributed in the metal coating. 
     Although the invention has been described in detail for the purposes of illustration, it is to be understood that such detail is solely for the purpose of illustration and that variations can be made therein without departing from the spirit and scope of the invention except as it may be limited by the claims. 
     
                                           TABLE 1                                 
__________________________________________________________________________
Inorganic                                                                 
         supplier     Kempten GmbH                                        
particles                                                                 
         particle size                                                    
                      about 5 μm                                       
         density      3.25 g/cm.sup.3                                     
         specific surface area                                            
                      about 2 m.sup.2 /g                                  
silicium-                                                                 
         zeta potential without                                           
carbide  surfactant   -57 mV                                              
(&#34;Sic 1200&#34;)                                                              
         zeta potential with                                              
         surfactant in a concentra-                                       
         tion of                                                          
         a. 5 mg per g of particles                                       
                      -25 mV                                              
         b. 10 mg per g of particles                                      
                      +12 mV                                              
         c. 20 mg per g of particles                                      
                      +76 mV                                              
         content in the bath                                              
                      50 g/liter                                          
Surfactant                                                                
         type         cationic, FC-type                                   
         structure                                                        
                       ##STR8##                                           
         content relative to the                                          
         inorganic particles                                              
                      a. 5 mg surf./gram of particles                     
                      b. 10 mg surf./gram of particles                    
                      c. 20 mg surf./gram of particles                    
electrolyte                                                               
bath     NiSO.sub.4 . 6 H.sub.2 O                                         
                      240 g/l                                             
         NiCl.sub.2 . 6 H.sub.2 O                                         
                      40 g/l                                              
         H.sub.3 BO.sub.3                                                 
                      40 g/l                                              
Watt&#39;s nickel                                                             
plating bath                                                              
         pH           4.2                                                 
         temperature  52° C.                                       
         bath vessel  2000 ml-beaker                                      
         anode        bent nickel plate                                   
         cathode      stainless steel bar, 4mm,                           
                      diam., 60 mm long                                   
         current density                                                  
                      10 A/dm.sup.2                                       
         bath agitation                                                   
                      moderate (with magnetic                             
                      stirrer)                                            
         electroplating time                                              
                      15 minutes                                          
dispersing of                                                             
         stirrer      Ultra Turrax                                        
mixture, stirrer speed                                                    
                      10 0000 r.p.m.                                      
electrolyte,                                                              
         stirring time                                                    
                      1 minute                                            
particles and                                                             
         rating of mixture with:                                          
surfactant                                                                
         a. 5 mg surf. per g of part                                      
                      flocculent                                          
         b. 10 mg surf. per g of part                                     
                      very flocculent                                     
         c. 20 mg surf. per g of part                                     
                      homogeneous and stable                              
composite                                                                 
         volume percentage/distri-                                        
coating of nickel                                                         
         bution of incorporated                                           
and SiC particles                                                         
         particles with:                                                  
         a. 5 mg surf. per g of part                                      
                      9%/inhomogeneous                                    
         b. 10 mg surf. per g of part                                     
                      4%/inhomogeneous                                    
         c. 20 mg surf. per g of part                                     
                      57%/homogeneous                                     
         coating thickness                                                
                      30 μm                                            
__________________________________________________________________________
 
    
     
                       TABLE 2                                                     
______________________________________                                    
Inorganic                                                                 
         supplier         Norton, Rotterdam                               
particles                                                                 
         particle size    about 15 μm                                  
         density          3.25 g/cm.sup.3                                 
         specific surface area                                            
                          about 0.7 m.sup.2 /g                            
Silicium zeta potential without                                           
                          -38 mV                                          
carbide  surfactant                                                       
(&#34;SiC 500&#34;)                                                               
         zeta potential with sur-                                         
                          +65 MV                                          
         factant in a concentra-                                          
         tion of 25 mg per g of                                           
         particles                                                        
         content in the bath                                              
                          35 g/ liter                                     
surfactant                                                                
         type             Same as in Table 1                              
         structure                                                        
         content relative to                                              
                          25 mg of surfactant/                            
         the inorganic particles                                          
                          gram of particles                               
electrolyte                                                               
         NiSO.sub.4 . 6 H.sub.2 O                                         
                          240 g/l                                         
bath     NiCl.sub.2 . 6 H.sub.2 O                                         
                          40 g/l                                          
         H.sub.3 BO.sub.3 40 g/l                                          
Watt&#39;s nickel                                                             
         pH               4,1                                             
plating bath                                                              
         temperature      50° C.                                   
         bath vessel      1500 ml-beaaker                                 
         anode            nickel grains in bag                            
         cathode          stainless steel bar 4 mm                        
                          diam, 60 mm long                                
         current density  5 A/dm.sub.2                                    
         bath agitation   moderate                                        
         electroplating time                                              
                          150 minutes                                     
dispersing of                                                             
         stirrer          ultra Turrax                                    
mixture, stirrer speed    10 000 r.p.m.                                   
electrolyte,                                                              
         stirrer time 4 minutes                                           
particles                                                                 
and                                                                       
surfactant                                                                
composite                                                                 
         volume percentage /                                              
coating of                                                                
         distribution of in-                                              
nickel and                                                                
         corporated particles                                             
SiC particles                                                             
         with 25 mg of sur-                                               
         factant per g of                                                 
         particles        40%/homogeneous                                 
         coating thickness                                                
                          about 180 μm.                                
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                                           TABLE 3                                 
__________________________________________________________________________
Inorganic                                                                 
         supplier     Kempten GmbH                                        
particles                                                                 
         particle size                                                    
                      about 2 μm                                       
         density      2.52 g/cm.sup.3                                     
         specific surface area                                            
                      about 6 m.sup.2 /g                                  
boron carbide                                                             
         zeta-potential without                                           
(&#34;B.sub.4 C.sub.1500 &#34;)                                                   
         surfactant   -50 mV                                              
         zeta potential with sur-                                         
         factant in a concentration                                       
         of 50 mg per gramme of                                           
         particles    +72 mV                                              
         content in the bath                                              
                      30 g/l                                              
surfactant                                                                
         type         cationic FC-type                                    
         structure                                                        
                       ##STR9##                                           
         content relative to the                                          
                      50 mg surf./gram of particles                       
         inorganic particles                                              
electrolyte                                                               
         Ni (NH.sub.2 SO.sub.3).sub.2                                     
                      460 g/l                                             
bath     NiCl.sub.2   5 g/l                                               
         H.sub.3 BO.sub.3                                                 
                      40 g/l                                              
nickel sulfamate                                                          
         pH           4.1                                                 
bath     temperature  55° C.                                       
         bath vessel  2000 ml-beaker                                      
         anode        bent nickel plate                                   
         cathode      stainless steel bar 4 mm in                         
                      diam., 60 mm long                                   
         current density                                                  
                      15 A/dm.sup.2                                       
         bath agitation                                                   
                      moderate (with magn. stirrer)                       
         electroplating time                                              
                      15 minutes                                          
dispersing of                                                             
         stirrer      Ultra Turrax                                        
mixture, electro-                                                         
         speed of stirrer                                                 
                      10 000 r.p.m.                                       
lyte, particles                                                           
         stirring time                                                    
                      2 minutes                                           
and surfactant                                                            
composite coating                                                         
         volume percentage/dis-                                           
of nickel and                                                             
         tribution of incorporated                                        
B.sub.4 C particles                                                       
         particles with 50 mg of                                          
         surf. per g of particles                                         
                      45%/homogeneous                                     
         coating thickness                                                
                      50 μm                                            
__________________________________________________________________________
 
    
     
                       TABLE 4                                                     
______________________________________                                    
Inorganic  supplier      Starck, Berlin                                   
particles  particle size 5 to 6 μm                                     
           density       abt 6.2 g/cm.sup.3                               
           specific surface                                               
           area          abt 1.5 m.sup.2 /g                               
MoSi.sub.2 zeta-potential with                                            
           surfactant in a con-                                           
           centration of 30 mg                                            
           per gramme of                                                  
           particles content in                                           
                         abt +60 mV                                       
           the bath                                                       
surfactant type          Same as in Table 1                               
           structure                                                      
           content       30 mg of surf./gram                              
           relative to the                                                
                         of particles                                     
           inorganic particles                                            
electrolyte                                                               
bath       NiSO.sub.4 . 6H.sub.2 O                                        
                         240 g/l                                          
           NiCl.sub.2 . 6 H.sub.2 O                                       
                         40 g/l                                           
           H.sub.3 BO.sub.3                                               
                         40 g/l                                           
           pH            4.1                                              
           temperature   55° C.                                    
Watt&#39;s nickel                                                             
           bath vessel   2000 ml-beaker                                   
plating bath                                                              
           anode         bent nickel plate                                
           cathode       stainless steel bar,                             
                         4 mm diam., 60 mm long                           
           current density                                                
                         5 A/dm.sup.2                                     
           bath agitation                                                 
                         moderate (with magnetic                          
           electroplating time                                            
                         stirrer) 60 minutes                              
dispersing of mix-                                                        
           stirrer       Ultra Turrax                                     
ture, electrolyte                                                         
           stirrer speed 10 000 r.p.m.                                    
particles and                                                             
           stirring time 2 minutes                                        
surfactant                                                                
composite coating                                                         
           volume percentage/                                             
of nickel and                                                             
           distribution of                                                
molybdenum incorporated par-                                              
silicide   ticles with 30 mg                                              
           of surfactant per                                              
           g of particles                                                 
                         32%/homogeneous                                  
           coating thickness                                              
                         about 60 μm                                   
______________________________________                                    
 
    
     
                       TABLE 5                                                     
______________________________________                                    
Inorganic  supplier         Rudolf Spring                                 
                            A.G.                                          
particles  particle size    2 to 4 μm                                  
           density          3.25 g/cm.sup.3                               
           specific surface area                                          
                            3.9 m.sup.2 /g                                
           zeta-potential without                                         
Diamond    surfactant       -38 mV                                        
grade 3    zeta-potential with sur-                                       
           factant in a concentration                                     
           of 20 mg per gramme of                                         
           particles        +65 mV                                        
           content in the bath                                            
                            20 g/l                                        
surfactant type             as in Table 3                                 
           structure                                                      
           content relative to the                                        
                            20 mg of sur-                                 
           inorganic particles                                            
                            factant per                                   
                            g of particles                                
electrolyte                                                               
           Ni(NH.sub.2 SO.sub.3).sub.2                                    
                            460 g/l                                       
bath       NiCl.sub.2       5 g/l                                         
           H.sub.3 BO.sub.3 40 g/l                                        
           pH               4.1                                           
nickel sulfamate                                                          
           temperature      55° C.                                 
bath       bath vessel      2000 ml-beaker                                
           anode            bent nickel plate                             
           cathode          stainless steel bar,                          
                            4 mm in                                       
                            diam., 60 mm long                             
           current density  10 A/dm.sup.2                                 
           bath agitation   moderate (with                                
                            magnetic stirrer)                             
           electroplating time                                            
                            15 minutes                                    
dispersing of                                                             
           stirrer          Ultra Turrax -mixture, stirrer speed 10 000   
                            r.p.m.                                        
electrolyte,                                                              
           stirring time    2 minutes                                     
particles and                                                             
surfactant                                                                
composite  volume percentage/                                             
coating of nickel                                                         
           distribution of the in-                                        
and diamond                                                               
           corporated particles with                                      
powder     20 mg of surfactant per                                        
           g of particles   28%/                                          
           coating thickness                                              
                            homogeneous                                   
                            about 30 μm                                
______________________________________                                    
 
    
     
                       TABLE 6                                                     
______________________________________                                    
Inorganic  supplier        Alfa Products                                  
particles  particle size   about 2 μm                                  
           density         7.1 g/cm.sup.3                                 
           specific surface area                                          
                           0.85 m.sup.2 /g                                
chromium powder                                                           
           zeta-potential without                                         
           surfactant      -35 mV                                         
           zeta-potential with                                            
           surfactant                                                     
           in a concentration                                             
           of 25 mg per gramme of                                         
           particles       +55 mV                                         
           content in the bath                                            
                           50 g/l                                         
Surfactant type            as in Table 1                                  
           structure                                                      
           content relative to                                            
                           25 mg of surfactant                            
           the inorganic particles                                        
                           per 1 g of particles                           
electrolyte                                                               
           NiSO.sub.4 . 6 H.sub.2 O                                       
                           240 g/l                                        
bath       NiCl.sub.2 . 6 H.sub.2 O                                       
                           40 g/l                                         
           H.sub.3 BO.sub.3                                               
                           40 g/l                                         
           pH              4.1                                            
Watt&#39;s nickel                                                             
           temperature     50° C.                                  
plating bath                                                              
           bath vessel     2000 ml-beaker                                 
           anode           bent nickel plate                              
           cathode         stainless steel bar,                           
                           4 mm in diam,                                  
                           60 mm long                                     
           current density 5 A/dm.sup.2                                   
           bath agitation  moderate (with                                 
                           magnetic stirrer)                              
           electroplating time                                            
                           50 minutes                                     
dispersing of mix-                                                        
           stirrer         Ultra Turrax                                   
ture, electrolyte,                                                        
           stirrer speed   10 000 r.p.m.                                  
particles and                                                             
           stirring time   11/2  minutes                                  
surfactant                                                                
composite coating                                                         
           volume percentage/                                             
of nickel  distribution of                                                
and chromium                                                              
           incorporated particles                                         
powder     with 25 mg of surfactant                                       
           per 1 g of particles                                           
                           47%/homogeneous                                
           coating thickness                                              
                           about 52 μ                                  
______________________________________                                    
 
    
     
                                           TABLE 7                                 
__________________________________________________________________________
Inorganic  supplier    Kempten G.m.b.H.                                   
particles  particle size                                                  
                       about 5 μm                                      
           density     3.25 g/cm.sup.3                                    
           specific surface area                                          
                       about 2 m.sup.2 /g                                 
silicium   zeta-potential without                                         
carbide    surfactant  -57 mV                                             
(&#34;SiC 1200&#34;)                                                              
           zeta-potential with                                            
           surfactant in a                                                
           concentration of 30 mg                                         
           per 1 gramme of                                                
           particles   +65 mV                                             
           content in the bath                                            
                       50 g/l                                             
Surfactant type        cationic CH-type                                   
           structure                                                      
                        ##STR10##                                         
                        ##STR11##                                         
           content relative to                                            
           the inorganic particles                                        
                       30 mg of surfactant per 1 g                        
                       of particles                                       
electrolyte bath                                                          
           Ni (NH.sub.2 SO.sub.3).sub.2                                   
                       460 g/l                                            
           NiCl.sub.2  5 g/l                                              
           H.sub.3 BO.sub.3                                               
                       40 g/l                                             
           pH          4.2                                                
Nickel sulfamate                                                          
           temperature 55° C.                                      
bath       bath vessel 2000 ml-beaker                                     
           anode       nickel plate                                       
           cathode     stainless steel bar, 4 mm in                       
                       diam., 60 mm long                                  
           current density                                                
                       15 A/dm.sup.2                                      
           bath agitation                                                 
                       moderate (with magnetic                            
                       stirrer)                                           
           electroplating time                                            
                       15 minutes                                         
dispersing of mixture,                                                    
           stirrer     Ultra Turrax                                       
electrolyte, particles                                                    
           stirrer speed                                                  
                       10 000 r.p.m.                                      
and surfactant                                                            
           stirring time                                                  
                       2 minutes                                          
           rating of mixture with                                         
           30 mg of surfactant per                                        
           1 g of particles                                               
                       very flocculent                                    
composite coating                                                         
           volume percentage/                                             
of nickel and                                                             
           distribution of the                                            
silicium carbide                                                          
           incorporated particles                                         
           with 30 mg of surfactant                                       
           per 1 g of particles                                           
                       0%                                                 
           coating thickness                                              
                       about 50 μm                                     
__________________________________________________________________________
 
    
     
                                           TABLE 8                                 
__________________________________________________________________________
Inorganic                                                                 
         supplier      Kempten GmbH                                       
particles                                                                 
         particle size about 5 μm                                      
         density       3.25 g/cm.sup.3                                    
         specific surface area                                            
                       about 2 m.sup.2 /g                                 
         zeta-potential without                                           
         surfactant    -57 mV                                             
silicium zeta-potential with sur-                                         
carbide  factant in a concentration                                       
(&#34;SiC.sub.1200 &#34;)                                                         
         of 30 mg per 1 gramme                                            
         of particles  +90 mV                                             
         content in the bath                                              
                       50 g/l                                             
Surfactant                                                                
         type          cationic, CH-type                                  
         structure                                                        
                       C.sub.16 H.sub.33 --SO.sub.2 --NH--(CH.sub.2).sub.3
                        --.sup.⊕N--(CH.sub.3).sub.3                   
                       CH.sub.3 O--SO.sub.3                               
         content relative to the                                          
         inorganic particles                                              
                       30 mg of surfactant per 1 g of                     
                       particles                                          
electrolyte                                                               
bath     Ni(NH.sub.2 SO.sub.3).sub.2                                      
                       460 g/l                                            
         NiCl.sub.2    5 g/l                                              
         H.sub.3 BO.sub.3                                                 
                       40 g/l                                             
         pH            4.2                                                
nickel sulfamate                                                          
         temperature   55° C.                                      
bath     bath vessel   2000 ml-beaker                                     
         anode         nickel plate                                       
         cathode       stainless steel bar, 4 mm                          
                       in diam., 60 mm long                               
         current density                                                  
                       15 A/dm.sup.2                                      
         bath agitation                                                   
                       moderate (magnetic stirrer)                        
         electroplating time                                              
                       2 minutes                                          
dispersing of                                                             
         stirrer       Ultra Turrax                                       
mixture, elec-                                                            
         stirrer speed 10,000 r.p.m.                                      
trolyte, particles                                                        
         stirring time                                                    
                       2 minutes                                          
and surfactant                                                            
         rating of mixture with                                           
         30 mg of surfactant per                                          
         1 gramme of particles                                            
                       slightly flocculent                                
composite coating                                                         
         volume percentage/                                               
of nickel and                                                             
         distribution of in-                                              
silicium carbide                                                          
         corporated particles                                             
         with 30 mg of surfactant                                         
                       12%/inhomogeneous                                  
         per 1 gramme of particles                                        
         coating thickness                                                
                       50 μm                                           
__________________________________________________________________________
 
    
     
                                           TABLE 9                                 
__________________________________________________________________________
Inorganic                                                                 
         supplier    Kempten GmbH                                         
particles                                                                 
         particle size                                                    
                     about 5 μm                                        
         density     3.25 g/cm.sup.3                                      
         specific surface area                                            
                     about 2 m.sup.2 /g                                   
silicium zeta-potential without                                           
carbide  surfactant  -57 mV                                               
(&#34;SiC.sub.1200 &#34;)                                                         
         zeta-potential with                                              
         surfactant in a con-                                             
         centration of 30 mg per                                          
         1 gramme of particles                                            
                     +50 mV                                               
         content in the bath                                              
                     50 g/l                                               
Surfactant                                                                
         type        cationic, CHtype                                     
         structure                                                        
                      ##STR12##                                           
                      ##STR13##                                           
         content relative to the                                          
                     30 mg of surfactant per                              
         inorganic particles                                              
                     1 g of particles                                     
electrolyte                                                               
bath     Ni(NH.sub.2 SO.sub.3).sub.2                                      
                     460 g/l                                              
         NiCl.sub.2  5 g/l                                                
         H.sub.3 BO.sub.3                                                 
                     40 g/l                                               
         pH          4.2                                                  
nickel   temperature 55° C.                                        
sulfamate bath                                                            
         bath vessel 2000 ml-beaker                                       
         anode       nickel plate                                         
         cathode     stainless steel bar 4 mm in                          
                     diam. 60 mm long                                     
         current density                                                  
                     15 A/dm.sup.2                                        
         bath agitation                                                   
                     moderate (magn. stirrer)                             
         electroplating time                                              
                     15 minutes                                           
dispersing of                                                             
         stirrer     Ultra Turrax                                         
mixture, stirrer speed                                                    
                     10 000 r.p.m.                                        
electrolyte,                                                              
         stirring speed                                                   
                     2 minutes                                            
particles and                                                             
         rating of mixture                                                
surfactant                                                                
         with 30 mg of sur-                                               
         factant per 1 gramme                                             
         of particles                                                     
                     slightly flocculent                                  
composite coating                                                         
         volume percentage/                                               
of nickel and                                                             
         distribution of the                                              
silicium carbide                                                          
         incorporated particles                                           
         with 30 mg of surfac-                                            
                     10%/inhomogeneous                                    
         tant per 1 g of                                                  
         particles                                                        
         coating thickness                                                
                     50 μm                                             
__________________________________________________________________________
 
    
     
                                           TABLE 10                                
__________________________________________________________________________
Inorganic                                                                 
         supplier of MoS.sub.2                                            
                       Fluka A.G.                                         
particles                                                                 
         particle size abt 25 μm                                       
         density       4.8 g/cm.sup.3                                     
         specific surface area                                            
                       0.5 m.sup.2 /g                                     
silicium zeta-potential without                                           
carbide  surfactant                                                       
         of SiC        -55 mV                                             
         of MoS.sub.2  not measurable (strongly                           
as in example VIII                                                        
         with surfactant in a                                             
                       hydrophobic)                                       
and MoS.sub.2                                                             
         concentration of                                                 
         25 mg per g SiC                                                  
                       +65 mV                                             
         25 mg per g MoS.sub.2                                            
                       +55 mV                                             
         content in the bath                                              
                       25 g/l SiC and 25 g/l MoS.sub.2                    
Surfactant                                                                
         type          cationic, FC-type                                  
         structure                                                        
                        ##STR14##                                         
         content relative to the                                          
                       both for SiC and                                   
         inorganic particles                                              
                       MoS.sub.2 25 mg/l                                  
electrolyte                                                               
         NiSO.sub.4 . 6 H.sub.2 O                                         
                       240 g/l                                            
         NiCl.sub.2 . 6 H.sub.2 O                                         
                       40 g/l                                             
         H.sub.3 BO.sub.3                                                 
                       40 g/l                                             
         pH            4.2                                                
Watt&#39;s nickel                                                             
         temperature   52°  C.                                     
plating bath                                                              
         bath vessel   2000 ml-beaker                                     
         anode         bent nickel plate                                  
         cathode       stainless steel bar, 4 mm                          
                       in diam. 60 mm long                                
         current density                                                  
                       7.5 A/dm.sup.2                                     
         bath agitation                                                   
                       moderate (with magnetic                            
                       stirrer)                                           
         electroplating time                                              
                       30 minutes                                         
dispersing of mix-                                                        
         stirrer       Ultra Turrax (the two                              
ture, electrolyte      substances at once)                                
particles and                                                             
         stirrer speed 10 000 r.p.m.                                      
surfactant                                                                
         stirring time 2 minutes                                          
composite coating                                                         
         volume percentage/                                               
                       SiC : 27 volume %                                  
of nickel and                                                             
         distribution of incorporated                                     
                       MoS.sub.2 : 13 volume %                            
chromium powder                                                           
         particles with                                                   
                       both substances were                               
         25 mg/g for the two types                                        
                       homogeneously distributed                          
         of particles  within each other                                  
         coating thickness                                                
                       about 45 μm                                     
__________________________________________________________________________