Effects of sintering temperature on the microstructure evolution and mechanical properties of TiB2-20 wt% CoNi cermets

Abstract

Microstructure evolution and mechanical properties of TiB2-CoNi cermets at different sintering temperatures were investigated. A small amount of liquid phase appeared between 1362 ºC and 1398 ºC. Solid phase sintering mainly occurred below this temperature range, while liquid phase sintering mainly occurred above this temperature range. At around 1460 ºC, dissolution and re-precipitation occurred around TiB2 particles due to liquid phase migration. Only TiB2 and CoNi phases were detected on XRD patterns at different sintering temperatures. As the sintering temperature increased, the relative density, fracture toughness, transverse fracture strength, and hardness of cermets increased, while their porosity decreased. The main influencing factors on the properties of cermets sintered at 1460 ºC and above were the interface bonding strength and the grain size, while the porosity was the main influencing factor for cermets sintered below 1460 ºC.