GB1231084A - - Google Patents

Abstract

1,231,084. Tungsten carbide-cobalt bodies. E.I. DU PONT DE NEMOURS & CO. July 16, 1968 [Aug.16, 1967], No.33869/68. Addition to 1,134, 022. Headings C7A and C7D. A consolidated body having a density over 95% of theoretical comprises tungsten carbide grains having a ratio of the longest dimension to the shortest dimension not exceeding 3:1 and a mean grain size less than 1Á, at least 60% of the grains being smaller than 1Á, bonded with Co containing 8-33 wt.% of W, the Co content of the body being 1-30 wt.%. The WC is preferably C deficient with 0À81-1 atomic wts. of C per atomic wt. of W. The interdispersion of WC and Co from which the body is made may be produced by extensive milling in vacus or an inert atmosphere of the carbide and Co in a liquid medium such as acetone. Additions of W, Ta, Nb, Zr or Ti may be made if necessary to create a C deficiency. After drying, free C and O 2 may be removed by treatment of the powder at 750‹ -1, 000‹ C. in a stream of H 2 containing CH 4 and inert carrier gas such as Ar. The composition in powder or in pre-compacted form is next heated in vacus, an inert atmosphere or in H 2 , at a temperature which is above 1000‹ C. but below the final consolidating temperature: this step results in the transfer of W into the Co. For consolidation, the powder is hot pressed in a graphite mould. Preferably the powder is first pressed at 200-500 p.s.i., brought to maximum temperature with no pressure applied, and then maximum temperature and pressure are applied until complete densification is attained. The bodies are useful as tools for cutting, drilling, shaping and punching, as dies, saws, knives, and as parts of valves and pumps, and for bearings.