The Influence of TaC Addition on High Temperature Strength of WC-10%Co Cemented Carbide

Abstract

The transverse-rupture strength of WC-TaC-100%Co alloys containing TaC up to 10% was investigated mainly in the temperature range from 600 to 900°C in relation to the fracture source. The WC-10%Co two-phase alloy (its mean carbide grain size is about 1.4μ) and WC-(1, 5, 10)%TaC-10%Co three-phase alloys (about 1.3μ) were used as specimens. The strength test was carried out according to the Japanese Industrial Standard.
The results obtained were as follows; (1) The fracture source in the TaC contained alloys was similar to those found in WC-Co alloy; that is, the structural defects were observed as the source below about 600°C and the regions of stable crack propagation were observed above about 600-700°C. (2) The intrinsic strength, i.e., the strength of TaC contained alloys being free from defects sharply decreased at about 600-700°C also in the same way as WC-Co alloy. The difference in the strength between the TaC contained alloy and WC-Co alloy decreased with increasing temperature up to about 800°C, and above this temperature the strength of TaC contained alloys was considered to correspond to that of WC-Co alloy in contrast to the general knowledge, when the carbon contents of the alloy were the same.