GB600066A - Method of producing hard metal composition - Google Patents

Abstract

A hard wear-resisting composition comprises the carbides of two or more metals, e.g. titanium, tantalum, columbium, vanadium, chromium, tungsten, or molybdenum, prepared by forming a porous body from minute particles of the metals and exposing it at elevated temperatures to the action of a carburizing-agent. The metals are first comminuted or otherwise reduced to fine size, preferably of an average diameter of a few microns, and are pressed to shape. The shaped body is then introduced into a furnace heated to 1000-1400 DEG C., into which carbonaceous gases, e.g. a hydrocarbon such as methane, are passed. The extent of carburization is controlled by adjusting the pressure or by diluting with a neutral gas such as desiccated hydrogen. If carbon monoxide is employed, a reducing-gas such as lithium vapour is added. Alternatively, the gas may be produced by introducing carbonyls into the furnace. The body may be first subjected to a vacuum at 500-800 DEG C., e.g. in a compartment of the furnace, from which the body may be passed into the carburizing - compartment and thence into a cooling-compartment in which a neutral atmosphere, e.g. of nitrogen, or a vacuum is maintained.ALSO:A hard, wear-resisting composition for use in cutting, boring, drilling, milling, planing, or otherwise working metals, glass, or other tough or brittle materials, and consisting of two or more hard metal carbides with a relatively-small amount of a low-melting metal binder, is prepared by forming a porous body from minute particles of the metals of the carbides, exposing it at elevated temperatures to the action of a carburising - agent, and finally filling the pores with the binding-metal. A mixture of two or more carbides of titanium, tantalum, columbium, vanadium, chromium, tungsten, or molybdenum may be used, while the binding-metal, which may comprise 3-40 per cent of the whole composition, may be nickel or cobalt, a tungsten-chromium-cobalt or bronze base alloy, or, provided precautions to prevent decarburisation of the carbide are taken, iron, steel, or alloy steel; other metals which do not normally wet the carbide particles may be employed if they be first alloyed with a metal having such wetting-properties. The metals to be carburised are first comminuted or otherwise reduced to fine size, preferably of an average diameter of a few microns, and are pressed into a shape similar to that of the final body, an organic lubricant being used if large bodies or complicated shapes are required. The shaped body is then introduced into a furnace, heated to 1,000-1,400 degrees C., into which carbonaceous gases, e.g. a hydrocarbon such as methane, are passed, the body preferably travelling through the furnace from one end while the gas is introduced at the other. The extent of carburisation is controlled by adjusting the pressure or by diluting with a neutral gas such as desiccated hydrogen. If carbon monoxide is employed, a reducing-gas such as lithium vapour is added. Alternatively, the gas may be produced by introducing carbonyls into the furnace. The porous body is then compressed and/or heated to reduce the volume of the pores to the desired amount. The binding-metal is then melted in contact with the body and allowed to fill the pores. The body may be first subjected to a vacuum at 500-800 degrees C. e.g. in a compartment of the furnace, from which the body may be passed into the carburising-compartment and thence into a cooling-compartment in which a neutral atmosphere, e.g. of nitrogen, or a vacuum is maintained. If nickel or cobalt is used as the binding-metal, it may be allowed to infiltrate slowly and alloy with the tungsten, but iron should be caused to infiltrate rapidly and the mass should then be cooled quickly below 800 degrees C. to avoid decarburisation of the tungsten carbide. According to the Specification as open to inspection under Sect. 91 the use of a single carbide is also described. This subject-matter does not appear in the Specification as accepted.