GB970734A - Improvements in or relating to the preparation of a mixture containing a metal carbide - Google Patents

Abstract

A mixture consisting of a carbide of a carburizable metal with a non-carburizable metal or with a carbide of another carburizable metal is prepared by drying a flowable composition of a volatile liquid containing dissolved decomposable compounds of said metals above the decomposition temperature of said compounds and simultaneously decomposing said decomposable compounds in such a manner as to drive off a substantial amount of the volatile solvent while avoiding segregation of the resulting compounds, grinding and reducing the product and carburizing any carburizable metal therein. The mixture prepared may be a single carbide-single non-carburizable binder metal mixture, a multi-carbide multi-non-carburizable binder metal mixture or a mixture of multi-carbides of metals, and cemented carbide strip may be formed from such mixtures. The drying of the flowable composition may be effected by drying it in the form of droplets or in the form of a thin film. Preferably the volatile liquid is a solvent for the decomposable compounds and the flowable composition is a true solution. The powder after carburization may be added to a further flowable composition consisting of a volatile liquid and a decomposable compound of a further metal capable of decomposition to a further reducible compound then forming in powdered form a mixture of said further reducible compound and the carburized powder and reducing the mixture. In the examples a Co-WC mixture is prepared by mixing solutions of cobalt powder dissolved in nitric acid and an aqueous ammonium metatungstate, drying the mixture in a rotary drum drier at 250 DEG C., heating the homogeneous product at 600 DEG C., grinding the product and then reducing it and finally mixing the reduced material with lamp-black and heating. Strips and bars may be made from the product. (7) A TiC-WC-Co mixture is prepared by mixing a TiC-WC powder prepared according to the invention with an aqueous solution containing Co(C2H3O2)2.4H2O, mixing the mixture and heating it on a drum drier, then further heating it, followed by grinding and reducing. In other examples the following mixtures are formed: (a) Mo2C-WC-Co-Ni, and (b) VC-Mo2C-Ni. Prior to the carburization, the powdered product of the reduction step may be blended with solid carbon and formed into a strip or bar. Alternatively the reduction and carburization may be carried out simultaneously.ALSO:A mixture consisting of a carbide of a carburizable metal with a non-carburizable metal or with a carbide of another carburizable metal is prepared by drying a flowable composition of a volatile liquid containing dissolved decomposable compounds of said metals above the decomposition temperature of said compounds and simultaneously decomposing said decomposable compounds in such a manner as to drive off a substantial amount of the volatile solvent whilst avoiding segregation of the resulting compounds, grinding and reducing the product and carburizing as carburizable metal therein. The mixture prepared may be a single carbide-single non-carburizable binder metal mixture, a multi-carbide multi-noncarburizable binder metal mixture or a mixture of multi-carbides of metals, and cemented carbide strip may be formed from such mixtures. The drying of the flowable composition may be effected by drying it in the form of droplets or in the form of a thin film. Preferably the volatile liquid is a solvent for the decomposable compounds and the flowable composition is a true solution. The powder after carburization may be added to a further flowable composition consisting of a volatile liquid and a decomposable compound of a further metal capable of decomposition to a further reducible compound, then forming in powdered form a mixture of said further reducible compound and the carburized powder and reducing the mixture. In the examples: (1) a WC-Co mixture is prepared by mixing solutions of cobalt powder dissolved in nitric acid and an aqueous ammonium metatungstate, drying the mixture in a rotary drum dryer at 250 DEG C., heating the homogeneous product at 600 DEG C., grinding the product, reducing it and finally mixing the reduced material with lamp-black and heating. Strips and bars may be made from the product; (7) a TiC-WC-Co mixture is prepared by mixing a TiC-WC powder prepared according to the invention with an aqueous solution containing Co(C2H3O2)2.4H2O, mixing the mixture and heating it on a drum dryer, then further heating it, then grinding and reducing the mixture. In other examples the following mixtures are formed: (a) Mo2C-WC-Co-Ni, (b) VC-Mo2C-Ni. Prior to the carburization the powdered product of the reduction step may be blended with solid carbon and formed into a strip or bar. Alternatively the reduction and carburization may be carried out simultaneously.