Effect of Sintering Atmosphere on The Mechanical Properties of Sintered Tungsten Carbide

Abstract

One of the crucial stages in fabrication of WC-Co composite is sintering process. Inappropriate sintering state, especially sintering temperature will lead to an abnormal grain growth and thus reduce the mechanical properties of the sintered parts. Sintering atmosphere also plays a big role in oxidation, carburizing, decarburizing and nitriding on the surface of sintered parts. Prevention of any unwanted process during sintering is demanded to maintain the performance of WC-CO composites without any by-products. In this work, the effect of different sintering atmosphere and sintering temperatures was studied on the mechanical properties of WC-Co composites. 95% nitrogen (N2) mixed with 5% hydrogen (H2) gases was used as sintering atmosphere in a tube furnace whereas vacuum atmosphere was carried out in vacuum furnace. The sintering process was conducted at 1300°C and 1400°C, respectively. Higher relative density, hardness and transverse rupture strength (TRS) were observed on the sintered parts. Sintering under N2-H2 atmosphere exhibited better mechanical properties. Low mechanical properties observed in vacuum atmosphere was probably due to over-sintering which led to grain growth activities and formation of η-phase.