Method of bonding silicon carbide body to a metal part
United States Patent [191 Ingleby Apr. 1,1975  
 [ METHOD OF BONDING SILICON CARBIDE BODY TO A METAL PART [75] Inventor: Bryan Edward Ingleby, Preston,  
 England [73] Assignee: United Kingdom Atomic Energy Authority, London, England [22] Filed: Mar. 12, 1974 [21] Appl. N0.: 450,293  
 [30] Foreign Application Priority Data Mar. 22, 1973 United Kingdom 13973/73 [52] US. Cl. 29/473.l 204/32 R [51] Int. Cl. B23k 31/02 [58] Field of Search 29/4731, 502; 204/32 R,  
 [56] References Cited UNITED STATES PATENTS 2,885,329 5/1959 Slatin 204/32 R 3,620,799 11/l97l Hoelscher... 29/473.1 X  
 Miyata et al. Heap et al.  
  204/32 R 29/473.l X  
 Primary Examiner-Carl E. Hall Attorney, Agent, or FirmLarson, Taylor and Hinds 6 Claims, No Drawings METHOD OF BONDING SILICON CARBIDE BODY TO A METAL PART BACKGROUND OF THE INVENTION This invention relates to silicon carbide bodies.  
  There is a requirement for the bonding of metal parts to self-bonded silicon carbide bodies, that is bodies which are formed from a pressed mixture of green silicon carbide and carbon by treatment with molten silicon or silicon vapour.  
 SUMMARY OF THE INVENTION According to the present invention a self-bonded silicon carbide body is treated to remove free silicon from the surface of the body and electro-plated with a metal. The metal plating may be subsequently bonded to a metal part, by brazing for example.  
  Nickel is a metal which can be satisfactorily plated. Copper is an alternative.  
  The preplating treatment of the silicon carbide body to remove free silicon may be effected by immersion in caustic alkali, for example sodium hydroxide, or in a hydrofluoric acid/nitric acid mixture.  
  In an example of a preferred way of carrying the invention into effect a self-bonded silicon carbide body was leachedin boiling 30% caustic soda solution for several hours in order to remove free silicon from the surface layer. The body was then plated with nickel using a standard plating solution of the following composition:  
 Nickel chloride 100 parts Nickel sulphate 600 parts Boric acid 70 parts Sodium formate 30 parts Tcepol 40 parts Water 2000 parts The nickel plating was carried out at 60C with a nickel anode and the silicon carbide body as cathode.  
 LII  
 The voltage was adjusted and plating commenced with a current of A amp until the initial bond and a com plete plated layer had formed. The current was then increased up to 1 amp and plating continued until the required thickness has been obtained, for example between 0.020 and 0.050 inch.  
  A silicon carbide body plated in the manner described in the example so as to receive a plating layer 0.020-0.050 in thick has been bonded to stainless steels using as braze material common silver solder of composition 50% silver, 15 copper, 16 zinc and 19% cadmium. The flux used was Easyflo stainless steel grade which was supplied by Johnson Matthey Ltd, 81 l-Iatton Garden, London, England.  
 I claim:  
  1. A process for joining a metal part to a self-bonded silicon carbide body, the process comprising the steps of treating the silicon carbide body to remove free silicon from the surface of the body, electroplating the treated body with a metal and bonding the metal plating to a metal part.  
  2. A process for joining a metal part to a self-bonded silicon carbide body as claimed in claim 1 wherein the electroplated metal is nickel.  
  3. A process of joining a metal part to a self-bonded silicon carbide body as claimed in claim 1 wherein the electroplated metal is copper.  
  4. A process ofjoining a metal part to a self-bonded silicon carbide body as claimed in claim 1 wherein the free silicon is removed by immersion of the body in caustic alkali.  
  5. A process of joining a metal part to a self-bonded silicon carbide body as claimed in claim 1 wherein the free silicon is removed by immersion of the body in a hydrofluoric acid/nitric acid mixture.  
  6. A process of joining a metal part to a self-bonded silicon carbide body as claimed in claim 1 wherein the metal part is of stainless steel.