Slide surface construction
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a slide surface construction constituting a slide surface for a mating member. 
     2. Description of the Prior Art 
     An example of such conventionally known slide surface construction is an Fe-plated layer which is formed around the outer peripheral surfaces of a land portion and a skirt portion of a base material of an aluminum alloy, for example, in a piston for an internal combustion engine, in order to improve the wear resistance of the piston. 
     However, under existing circumstances where a high speed and a high output of the internal combustion engine are desired, the prior art slide surface constructions suffer from problems of insufficient oil retaining property, i.e., oil retention, and poor initial conformability and seizure resistance. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a slide surface construction of the type described above, which has a sufficient oil retention and a good initial conformability by specifying the crystal structure, thereby providing an improved seizure resistance. 
     To achieve the above object, according to the present invention, there is provided a slide surface construction, which is formed of an aggregate of metal crystals having a body-centered cubic structure, the aggregate including at least one of two types of metal crystals: (h00) oriented metal crystals with their (h00) planes (by Miller indices) oriented toward a slide surface and having a content S in a range represented by S&lt;25%, and (3hh0) oriented metal crystals with their (3hh0) planes (by Miller indices) oriented toward the slide surface and having a content S in a range represented by S&lt;25%. 
     If the (h00) oriented metal crystals with their (h00) planes (by Miller indices) oriented toward the slide surface and/or the (3hh0) oriented metal crystals with their (3hh0) planes (by Miller indices) oriented toward the slide surface are present in the above-described concentrations in the aggregate of the metal crystals having the body-centered cubic structure, a large number of relatively large pyramid-shaped (and/or truncated pyramid-shaped) metal crystals are precipitated in the slide surface into mutually biting states. As a result, the slide surface takes on an intricate morphology comprising a large number of fine crests, a large number of fine valleys formed between the crests, and a large number of swamps formed due to the mutual biting of the crests. Therefore, the slide surface construction has an improved oil retention. In addition, the initial conformability of the slide surface construction is enhanced by the preferential wearing of tip ends of the pyramid-shaped metal crystals. Thus, the slide surface construction exhibits an excellent seizure resistance. However, if the content S of the (h00) oriented metal crystals is equal to or more than 25%, or if the content S of the (3hh0) oriented metal crystals is equal to or more than 25%, the morphology of the slide surface tends to be simplified with an increase in content of the oriented metal crystals and hence, the oil retention and initial conformability of the slide surface construction are reduced. 
     The above and other objects, features and advantages of the invention will become apparent from the following description of a preferred embodiment, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a piston; 
     FIG. 2 is a sectional view taken along line 2--2 in FIG. 1; 
     FIG. 3 is a perspective view illustrating a body-centered cubic structure and its (h00) and (3hh0) planes; 
     FIG. 4 is a perspective view of an essential portion of one example of a slide surface construction; 
     FIG. 5 is a sectional view taken along line 5--5 in FIG. 4; 
     FIG. 6 is a diagram for explaining an inclination of the (h00) plane in the body-centered cubic structure; 
     FIG. 7 is an X-ray diffraction pattern for a first example of the slide surface construction; 
     FIG. 8 is a photomicrograph showing the crystal structure of the slide surface in the first example of the slide surface construction; 
     FIG. 9 is an X-ray diffraction pattern for a second example of the slide surface construction; 
     FIG. 10 is a photomicrograph showing the crystal structure of the slide surface in the second example of the slide surface construction; 
     FIG. 11 is a photomicrograph showing the crystal structure of the slide surface in a third example of the slide surface construction; 
     FIG. 12 is a graph illustrating the relationship between the content of {200} oriented Fe crystals and the seizure generating load; 
     FIG. 13 is a plane view illustrating crystal planes located on slants at a trigonal pyramid-shaped tip end portion; 
     FIG. 14 is a plan view illustrating crystal planes located on slants in one example of a hexagonal pyramid-shaped tip end portion; 
     FIG. 15 is a plan view illustrating crystal planes located on slants in another example of a hexagonal pyramid-shaped tip end portion; 
     FIG. 16 is a perspective view illustrating crystal planes located on slants and end faces of a small pyramid-shaped tip end portion; and 
     FIG. 17 is a plane view illustrating the crystal planes located on slants of a quadrangular pyramid-shaped tip end portion. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 and 2, a piston 1 for an internal combustion engine includes a base material 2 of an aluminum alloy. A lamellar slide surface construction 4 is formed by plating on outer peripheral surfaces of a land portion 3 1  and a skirt portion 3 2  of the base material 2. 
     As shown in FIGS. 3 and 4, the slide surface construction 4 is formed of an aggregate of metal crystals having a body-centered cubic structure (bcc structure). The aggregate includes (h00) oriented metal crystals with their (h00) planes oriented toward the slide surface 4a for an inner wall 5 of a cylinder bore and/or (3hh0) oriented metal crystals with their (3hh0) planes oriented toward the slide surface 4a for the inner wall 5. The content S of the (hh0) oriented crystals and the (3hh0) oriented crystals are set in a range represented by S&lt;25%, respectively. 
     For example, if both the oriented metal crystals are present at the levels in the above-described ranges, a large number of relatively large pyramid and/or truncated pyramid-shaped, e.g., trigonal pyramid-shaped (in the illustrated embodiment) metal crystals 6 are precipitated in the slide surface 4a into mutually biting states. Thus, the slide surface 4a takes on an intricate morphology comprising a large number of fine crests 7, a large number of fine valleys 8 between the crests 7, and a large number of fine swamps 9 formed due to the mutual biting of the crests 7. Therefore, the slide surface construction 4 has good oil retention. In addition, the tip ends of the trigonal pyramid-shaped metal crystals are preferentially worn, thereby providing an improved initial conformability to the slide surface construction 4. 
     As shown in FIG. 6, the inclination of the (h00) plane with respect to a phantom plane 10 along the slide surface 4a will cause an inclination of the trigonal pyramid-shaped metal crystal 6 and hence, an influence is imparted to the oil retention and initial conformability of the slide surface construction 4. Thereupon, the inclination angle formed by the (h00) plane with respect to the phantom plane 10 is set in a range represented, by 0°≦θ≦15°. The inclination angle θ of the (3hh0) plane is likewise set in a range represented by 0°≦θ≦150°. In this case, the direction of the inclination of the (h00) and (3hh0) planes is not limited. If the inclination angle of the (h00) and (3hh0) planes is larger than 15°, the oil retention and the initial conformability of the slide surface construction 4 are reduced. 
     Examples of the metal crystal having the bcc structure are those of simple metals such as Fe, Cr, Mo, W, Ta, Sr, Nb, V, etc., and the alloys thereof. 
     In the plating treatment for forming the slide surface construction 4 according to the present invention, basic conditions for the electrolytic deposition of the Fe-plating are shown in Tables 1 and 2. 
     
                       TABLE 1                                                     
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Plating bath composition (g/liter)                                        
Ferrous                                                                   
sulfate                                                                   
       Boric acid                                                         
                 Ammonium sulfate                                         
                               Organic additive(s)                        
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150˜400                                                             
       5˜50                                                         
                 50˜200  10˜150                               
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                       TABLE 2                                                     
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Treating conditions                                                       
Plating bath                                                              
         Plating bath temperature                                         
                         Cathode current density                          
pH       (°C.)    (A/dm.sup.2)                                     
______________________________________                                    
2˜6.5                                                               
         10˜60     0.1˜3                                      
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     In the electrolytic deposition of the Fe-plating under the above-described conditions, the precipitation and content of the (h00) and (3hh0) oriented Fe crystals are controlled by the cathode current density, the pH of the plating bath, the amount of organic additive incorporated and the like. 
     In addition to the electrolytic plating processes, examples of other plating treatments that may also be used include PVD processes, CVD processes, sputtering processes, ion plating and the like, which are gas-phase plating processes. Conditions for W- or Mo-plating by a sputtering process are, for example, an Ar pressure of 0.2 to 1 Pa, an Ar acceleration power of 0.1 to 1.5 kW in direct current; and a base material temperature of 80 to 300° C. Conditions for W-plating by a CVD process are, for example, a WF 6  starting material; a gas flow rate of 2 to 15 cc/min.; a pressure of 50 to 300 Pa within the chamber; and a base material temperature of 300 to 600° C. 
     Particular examples will be described below. 
     A plurality of pistons 1 for internal combustion engines were produced by subjecting the outer peripheral surfaces of a land portion 3 1  and a skirt portion 3 2  of a base material of an aluminum alloy to an electrolytic Fe-plating process to form a slide surface construction 4 comprised of an aggregate of Fe crystals. 
     Tables 3 to 6 show the conditions for the electrolytic Fe-plating process for examples 1 to 17 of the slide surface constructions 4, wherein Tables 3 and 5 show the plating bath composition, and Tables 4 and 6 show the treating conditions. 
     
                       TABLE 3                                                     
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Plating bath composition (g/liter)                                        
Example Ferrous   Boric   Ammonium                                        
No.     sulfate   Acid    sulfate Urea Saccharin                          
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1       230       30      100     100  1                                  
2       230       30      100     100  1                                  
3       230       30      100     100  1                                  
4       230       30      100     100  1                                  
5       230       30      100     100  1                                  
6       230       30      100     100  0.4                                
7       230       30      100     100  1                                  
8       230       30      100     100  1                                  
9       230       30      100     100  0.4                                
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                       TABLE 4                                                     
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Treating conditions                                                       
Example Plating   Plating bath  Cathode current                           
No.     bath pH   temperature (°C.)                                
                                density (A/dm.sup.2)                      
______________________________________                                    
1       6         50            0.2                                       
2       6         50            1                                         
3       6.2       50            0.2                                       
4       5.1       50            1                                         
5       5.8       50            1                                         
6       4         50            1                                         
7       2.8       50            1                                         
8       6.2       50            1                                         
9       4.2       50            5                                         
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                       TABLE 5                                                     
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Plating bath composition (g/liter)                                        
Example Ferrous   Boric   Ammonium                                        
No.     sulfate   Acid    sulfate Urea Saccharin                          
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10      230       30      100     100  0.4                                
11      230       30      100     100  0.4                                
12      230       30      100     100  0.4                                
13      300       30      100      20  0.4                                
14      300       30      100      20  1                                  
15      300       30      100      20  1                                  
16      300       30      100      20  0.4                                
17      230       30      100     100  0.4                                
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                       TABLE 6                                                     
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Treating conditions                                                       
Example Plating   Plating bath  Cathode current                           
No.     bath pH   temperature (°C.)                                
                                density (A/dm.sup.2)                      
______________________________________                                    
10      4         50            5                                         
11      3.2       50            7                                         
12      2.7       50            7                                         
13      3.3       50            10                                        
14      5.4       50            10                                        
15      6.2       50            6                                         
16      3.3       50            8                                         
17      3.5       50            7                                         
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     Tables 7 and 8 show the crystal shape of the slide surface 4a, the grain size of the Fe crystals, the content S of the oriented Fe crystals and the hardness for Examples 1 to 17. 
     
                                           TABLE 7                                 
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     Crystal                                                              
     shape of                                                             
          Grain                    Hard-                                  
Example                                                                   
     slide                                                                
          size Content S of oriented Fe crystals (%)                      
                                   ness                                   
No.  surface                                                              
          (μm)                                                         
               {110}                                                      
                   {200}                                                  
                       {211}                                              
                           {310}                                          
                               {222}                                      
                                   (HV)                                   
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1    AHP* about 8                                                         
               16.6                                                       
                   1.8 29.3                                               
                           1.7 50.6 1                                     
                                   278                                    
2    Trigonal                                                             
          about 10                                                        
               32.8                                                       
                   1.2 20.8                                               
                           2.2 43  302                                    
     pyramid                                                              
3    Trigonal                                                             
          about 8                                                         
               20  4   20  6   50  300                                    
     pyramid                                                              
     SP*  about 1                                                         
4    Trigonal                                                             
          about 8                                                         
               20.7                                                       
                   3.3 30  5.4 40.6                                       
                                   400                                    
     pyramid                                                              
     SP*  about 1                                                         
5    Trigonal                                                             
          about 8                                                         
               30  6   15  9   40  270                                    
     pyramid                                                              
     Plate-like                                                           
6    Trigonal                                                             
          about 8                                                         
               30  8   10  12  40  310                                    
     Pyramid                                                              
     Plate-like                                                           
7    Trigonal                                                             
          about 6                                                         
               20  12  30  18  20  410                                    
     pyramid                                                              
     SP*  about 1                                                         
8    Trigonal                                                             
          about 8                                                         
               10  15  15  20  40  310                                    
     pyramid                                                              
     Very fine                                                            
          ≦0.5                                                     
     grain                                                                
9    Trigonal                                                             
          about 8                                                         
               12  23  15  10  40  280                                    
     pyramid                                                              
     Very fine                                                            
          ≦0.5                                                     
     gain                                                                 
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 AHP* = Approximately hexagonal pyramid                                   
 SP* = Small pyramid                                                      
 
    
     
                                           TABLE 8                                 
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     Crystal                                                              
     shape of                                                             
          Grain                    Hard-                                  
Example                                                                   
     slide                                                                
          size Content S of oriented Fe crystals (%)                      
                                   ness                                   
No.  surface                                                              
          (μm)                                                         
               {110}                                                      
                   {200}                                                  
                       {211}                                              
                           {310}                                          
                               {222}                                      
                                   (HV)                                   
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10   Very fine                                                            
          about 0.5                                                       
               15  27  15  13  30  290                                    
     grain                                                                
     Partially                                                            
          about 5                                                         
     pyramid                                                              
11   Very fine                                                            
          &lt;0.5 15  30  15  20  20  190                                    
     grain                                                                
12   Very fine                                                            
          about 0.5                                                       
               16  34  10  19  21  280                                    
     grain                                                                
13   SP*  about 1                                                         
                2   0  75   0  23  580                                    
     Very fine                                                            
          about 0.5                                                       
     grain                                                                
14   Very fine                                                            
          about 1                                                         
               10  10  40  25  15  290                                    
     grain                                                                
15   Plate-like                                                           
          about 8                                                         
               30  20  15  25  10  270                                    
     Very fine                                                            
          ≦0.5                                                     
     grain                                                                
16   Very fine                                                            
          ≦0.5                                                     
               20  20  15  25  20  320                                    
     grain                                                                
17   Very fine                                                            
          ≦0.5                                                     
               12  30  18  25  15  220                                    
     gain                                                                 
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 SP* = Small pyramid                                                      
 
    
     The content S was determined in the following manner on the basis of X-ray diffraction patterns (X-rays were applied in a direction perpendicular to the slide surface 4a) for the examples 1 to 17. Example 2 will be described below. FIG. 7 is an X-ray diffraction pattern for Example 2. The content S for each of the oriented Fe crystals was determined from each of following expressions. Here, the term &#34;{110} oriented Fe crystal&#34; means, for example, an oriented Fe crystal with its {110} plane oriented toward the slide surface 4a. 
     {110} oriented Fe crystals: S 110  ={(I 110  /IA 110 )/T}×100 
     {200} oriented Fe crystals: S 200  ={(I 200  /IA 200 )/T}×100 
     {211} oriented Fe crystals: S 211  ={(I 211  /IA 211 )/T}×100 
     {310} oriented Fe crystals: S 310  ={(I 310  /IA 310 )/T}×100 
     {222} oriented Fe crystals: S 222  ={(I 222  /IA 222 )/T}×100 
     wherein each of I 110 , I 200 , I 211 , I 310  and I 222  is a measurement (cps) of the intensity of X-rays reflected from each crystal plane; each of IA 110 , IA 200 , IA 211 , IA 310  and IA 222  is an intensity ratio of X-rays reflected from each crystal plane in an ASTM card. Further, IA 110  =100, IA 200  =20, IA 211  =30, IA 310  =12 and IA 222  =6. Furthermore, T=(I 110  /IA 110 )+(I 200  /IA 200 )+(I 211  /IA 211 )+(I 310  /IA 310 )+(I 222  /IA 222 ). 
     FIG. 8 is a photomicrograph showing the crystal structure of the slide surface 4a in the example 2. In FIG. 8, a large number of mutually bitten trigonal pyramid-shaped Fe crystals are observed. As shown in Table 7 and FIF. 7, the content S of the (h00), i.e., {200} oriented Fe crystals in the example 2 is equal to 1.2%, and the content S of the (3hh0), i.e., {310} oriented Fe crystals in the example 2 is equal to 2.2%. 
     FIG. 9 is an X-ray diffraction pattern of example 4, and FIG. 10 is a photomicrograph showing the crystal structure of the slide surface 4a in example 4. In FIG. 10, a large number of relatively large trigonal pyramid-shaped Fe crystals and a large number of small pyramid-shaped crystals are observed. It can be seen from FIG. 10 that oil swamps are formed between the trigonal pyramid-shaped Fe crystals, and oil swamps are formed even by the small pyramid-shaped Fe crystals precipitated in a very intricate state in the valleys thereof. As shown in Table 7 and FIG. 9, the content S of the {200} oriented Fe crystals in the example 4 is equal to 3.3%, and the content S of the (310) oriented Fe crystals in the example 4 is equal to 5.4%. 
     FIG. 11 is a photomicrograph showing the crystal structure of the slide surface 4a in the example 17. It can be seen from FIG. 11 that if the content S of the {310} oriented Fe crystals in the example 4 is equal to or more than 25%, the slide surface 4a assumes a simplified morphology and is smoothed. 
     A seizure test for the examples 1 to 17 was carried out in a chip-on-disk manner to determine the seizure generating load, thereby providing the results shown in Tables 9 and 10. Conditions for the test were as follows: the material of the disk was an Al-10% by weight of Si alloy; the rotational speed of the disk was 15 m/sec.; the amount of oil supplied was 0.3 ml/min.; and the area of the slide surface of a chip made from the slide surface construction was 1 cm 2 . 
     
                       TABLE 9                                                     
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Example No. Seizure generating load (N)                                   
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1           860                                                           
2           850                                                           
3           810                                                           
4           800                                                           
5           810                                                           
6           800                                                           
7           700                                                           
8           650                                                           
9           600                                                           
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                       TABLE 10                                                    
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Example No. Seizure generating load (N)                                   
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10          500                                                           
11          325                                                           
12          300                                                           
13          300                                                           
14          350                                                           
15          350                                                           
16          300                                                           
17          300                                                           
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     FIG. 12 illustrates the relationship between the content S of the {200} oriented Fe crystals and the seizure generating load for the examples 1 to 17, wherein a line x 1  indicates the relationship when the content S of the {310} oriented Fe crystals is less than 25%, and a line x 2  indicates the relationship when the content S of the {310} oriented Fe crystals is equal to 25%. As apparent from FIG. 12 and the examples 1 to 9, the seizure generating load can be increased to 550 N or more to enhance the seizure resistance by setting the content S of the {200} oriented Fe crystals in a range represented by S&lt;25% and setting the content S of the {310} oriented Fe crystals also in a range represented by S&lt;25%. However, if the contents S of the {200} and {310} oriented Fe crystals are equal to 0% as in the example 13, the seizure generating load is low. 
     Tables 11 and 12 shows the conditions for the electrolytic plating treatment used for examples 18 and 19 in which the content S of the {200} or {310} oriented Fe crystals was set at 0% in each of the slide surface constructions 4. 
     
                       TABLE 11                                                    
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Plating bath composition (g/liter)                                        
Example Ferrous   Boric   Ammonium                                        
No.     sulfate   Acid    sulfate Urea Saccharin                          
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18      230       30      100     100  1                                  
19      230       30      100     100  1                                  
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                       TABLE 12                                                    
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Treating conditions                                                       
Example Plating bath                                                      
                   Plating bath Cathode Current                           
No.     pH         temperature (°C.)                               
                                density (A/dm.sup.2)                      
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18      6.2        50           1.3                                       
19      6          50           1.5                                       
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     Table 13 shows the crystal shape of the slide surface 4a, the grain size of the Fe 3  crystals, the content S of the oriented Fe crystals and the hardness for the example 18 and 19. 
     
                                           TABLE 13                                
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     Crystal                                                              
     shape of                                                             
          Grain                    Hard-                                  
Example                                                                   
     slide                                                                
          size Content S of oriented Fe crystals (%)                      
                                   ness                                   
No.  surface                                                              
          (μm)                                                         
               {110}                                                      
                   {200}                                                  
                       {211}                                              
                           {310}                                          
                               {222}                                      
                                   (HV)                                   
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18   AHP* about 8                                                         
               10  3   17  0   70  305                                    
19   AHP  about                                                           
               12  0   15  3   70  310                                    
          10                                                              
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 AHP* = Approximately hexagonal pyramid                                   
 
    
     A seizure test for the examples 18 and 19 was carried out in a chip-on-disk manner under the same conditions as those described above. As a result, it was confirmed that the examples 18 and 19 had a seizure generating load of 940 N. Thus, if either the {200} oriented Fe crystals or the {310} oriented Fe crystals is present, the slide surface construction 4 has an excellent seizure resistance. In this case, when the content S of the {200} oriented Fe crystals is equal to 0%, the content S of the {310} oriented Fe crystals is less than 25%. On the other hand, when the content S of the {310} oriented Fe crystals is equal to 0%, the content S of the {200} oriented Fe crystals is less than 25%. 
     In the metal crystals having the body-centered cubic structure, the crystal shape produced on the slide surface, crystal planes located on the slants (which include the opposite triangular end faces in FIG. 16) and the like for the oriented metal crystals are shown in Table 14 . 
     
                                           TABLE 14                                
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       Crystal shape                                                      
               Crystal plane                                              
Oriented                                                                  
       on slide                                                           
               located on                                                 
                        Characteristic                                    
                                 Referential                              
metal crystal                                                             
       surface slant    slant    drawing                                  
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(hhh)  Trigonal                                                           
               (hh0) plane:                                               
                        High hardness,                                    
                                 FIG. 13                                  
       pyramid close-packed                                               
                        good                                              
               plane    wettability and                                   
                        good wear                                         
                        resistance                                        
       Hexagonal                                                          
               (hhh) plane:                                               
                        Excellent                                         
                                 FIG. 14:                                 
       pyramid 50%,     wettability                                       
                                 concave                                  
               5(hhh) plane:                                              
                        because of                                        
                                 slant                                    
               50%      (hhh) plane                                       
                                 FIG. 15:                                 
                        having a large                                    
                                 flat slant                               
                        surface energy                                    
               (hh0) plane: 50%                                           
                        High hardness,                                    
               (2hhh) plane: 50%                                          
                        good wettabilty                                   
               (hh0) plane: close-                                        
                        and good wear                                     
               packed plane                                               
                        resistance                                        
(2hhh) Small pyramid                                                      
               (hh0) plane:                                               
                        High hardness                                     
                                 FIG. 16                                  
               close-packed                                               
                        good                                              
               plane    wettability and                                   
                        good wear                                         
                        resistance                                        
(h00)  Quadrangular                                                       
               (hh0) plane:                                               
                        High hardness                                     
                                 FIG. 17                                  
       pyramid close-packed                                               
                        good                                              
               plane    wettability and                                   
                        good wear                                         
                        resistance                                        
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     It should be noted that for the wettability of the crystal planes located on the slants to oil or the like, the (hhh) plane is superior on the (hh0) plane. 
     The slide surface construction according to the present invention is applicable, for example, to the slide portion of any of following parts of an internal combustion engine: pistons (ring grooves), piston rings, piston pins, connecting rods, crankshafts, bearing metals, oil pump rotors, oil pump rotor housings, cam shafts, springs (end faces), spring seats, spring retainers, cotters, rocker arms, roller bearing outer cases, roller bearing inner cases, valve stems, valve faces, hydraulic tappets, water pump rotor shafts, pulleys, gears, transmission shaft portions, clutch plates, washers, and bolts (bearing surfaces and threaded portions).