GB762418A - Improved process and apparatus for the improvement of surfaces of metals, in particular iron and steel - Google Patents

Abstract

762,418. Coating with metals. NOWAK, R., and HASSE, E. June 23, 1954 [July 3, 1953], No. 18466/54. Class 82(2) In a process for the coating of metallic surfaces by diffusion, the workpieces to be treated are subjected to the action of such sub-halides of the diffusion element which react with the basic metal in the form of a heterogeneous chemical replacement reaction, the gases resulting from the diffusion treatment being continuously regenerated in a circulation system, by the diffusion element or a substance containing the diffusion element, to the subhalides of the diffusion element. Catalysts, e.g. FeCl 3 , FeCl 2 , SnCl 2 , SnCl 4 , AlCl 3 , AlBr 3 , BF 3 , BCl 3 , CuCl 2 , MgCl 2 , may be added to the reaction gases. Prior to coating, the metallic surface is chemically activated by oxidation and subsequent reduction. As shown, workpieces to be coated are heated to reaction temperature in chamber 1, oxidized in chamber 2, reduced in chamber 3, contacted with reaction gases in chamber 4 and cooled in chamber 5. Rotary blower 10 forces the reaction gases through the circulation system from the chamber 4, through pipe line 8, regeneration chamber 11, pipe line 9 and finally back into the chamber 4. In one example is described the siliconizing of steel plates wherein the process is started by introducing SiCl 4 + AlCl 3 into chamber 4, the SiCl 4 reacting with the plates to diffuse Si and release FeCl 2 which is regenerated by Si or FeSi in chamber 11 to the subchloride of silicon SiCl 2 , this reacting with the plates to diffuse Si and release FeCl 2 which is regenerated as before. The other examples describe (a) the siliconizing and aluminizing of cast-iron or steel bars (b) the titanium-coating of Mo wire and (c) the coating of iron and steel objects with Cu-Al.