SINTERED HARD ALLOY OF SUPER FINE GRAINS

摘要

PURPOSE:To lower sintering temp., to reduce grown grains, and to improve strength by substituting Co super fines for a part or all of Co fines in a sintered hard alloy of super fine grains consisting of a WC-base hard phase and a Co- base binding phase. CONSTITUTION:The sintered hard alloy is composed of, by weight, the 75-90% hard phase mainly composed of WC and the 10-25% binding phase mainly composed of Co. In the composition, the Co super fines of =0.1mum average grain size are substituted for a part or all of the Co fines so that the ratio super fines/(super fines + fines) is 1/10-1. By use of this Co super fine powder, sintering temp. can be lowered, by which the grain growth of a type of precipitative reaction by melting can be inhibited and fine structure can be obtained. Moreover, further substitution of TaC and NbC for 0.5-5% of the hard phase produces a more excellent effect.