| 摘要 |
In a method of producing coatings of hard carbides of the metals of the 3rd-6th groups, e.g. Ti, V, W, on metallic or non-metallic objects by reaction of halides of the metals with hydrogen and hydrocarbons, a gas mixture is used which contains hydrogen, an amount of volatile hydrocarbons not greater than that corresponding to equilibrium between carbon and hydrogen and the volatile hydrocarbons at the deposition temperature of 800-1200 DEG C., and an amount of metal halide which is no more than, but preferably is as much as, will react to form the metal carbide. The gas mixture may be produced (a) by the action of hydrogen halide and/or halogen, with or without hydrogen, on the carbide of the carbide-forming metal with or without free carbon, or (b) by passing hydrogen halide and/or halogen, with or without hydrogen, over the metal the carbide of which is to be formed and mixing the resultant hydrogen and metal halide with hydrogen and hydrocarbon, e.g. methane, (produced by passing hydrogen over carbon) in the coating zone. Coatings which consist of mixtures of carbides may be produced; nitrides may be incorporated in the coatings, e.g. by adding nitrogen and/or compounds giving up nitrogen or a gas containing nitrogen, such as ammonia, in the coating zone to the carbide-producing mixture. Various alloy steels are mentioned as base materials. After application of the coatings, the base materials may be hardened by heat-treatment in a protective atmosphere, preferably pure nitrogen, and quenching. The coatings may be used for the surface protection of tools, machine parts &c., such as files, rasps, bearings, valves, thread guides of spinning and drawing tools. |
