GB594068A - An improved hard composition and method of manufacturing same - Google Patents

Abstract

Sintered hard compositions are made by forming a powder mixture from grains of aluminium oxide and at least one element of the group tungsten, molybdenum, tantalum, rhenium, osmium, ruthenium and iridium, the aluminium oxide amounting to from 52-98.5 per cent of the product, heating the mixture to a temperature sufficiently above the melting point of the aluminium oxide to cause the said element to become incorporated by fusion into the crystal structure of the aluminium oxide, solidifying the mass, crushing the mass to a powder, mixing the powder with another powder consisting of at least one metallic element of the group tungsten, molybdenum, tantalum, rhenium, osmium, ruthenium and iridium with or without the addition of at most 20 per cent of one or more of chromium, nickel, cobalt and iron, and of such weight and volume as to leave the aluminium oxide still predominant in weight and volume in the mixture and subjecting the mixture to a sintering process at a temperature sufficient to bring about atomic mobility of all the grains thereof. When more than one of the specified elements are to be fused with the aluminium oxide or added to the powder containing aluminium oxide prior to sintering, the said metals may be added in the form of alloys. The fusion of the aluminium oxide with the specified metals may be omitted and the oxide sintered directly with one or more of tungsten, tantalum, molybdenum, osmium, rhenium, ruthenium and iridium with or without one or more of chromium, nickel, cobalt and iron. Sintering may be performed at a temperature from 1000 DEG C-2000 DEG C. in a protective atmosphere or vacuum.