Mechanical properties and high-temperature oxidation of (WC-12Co) + MoSi2 hardmetals

The present study used a spark plasma sintering technique to fabricate WC-12Co hardmetals with 0, 5, 10, and 15 wt% MoSi2 addition. The effect of MoSi2 concentration on structure, high-temperature oxidation, density, and hardness was investigated and clarified. Phase analysis reveals the formation of Co3Mo3C, WSi2, and Mo2C with the increase of MoSi2 content. At 700 °C, there is no significant difference between the oxidation resistance of WC-12Co and 5 wt% MoSi2 compacts. However, 10 and 15 wt% MoSi2 addition leads to a significant decrease in oxidation resistance, forming a thick and porous oxide layer. All compositions form mix oxide layer consisting mainly of CoWO4 and WO3 scales. The XRD quantitative analysis indicates that the mass fraction of the oxide scales strongly depends on the hardmetals constituent. High MoSi2 content results in the formation of a high fraction of WO3. Interestingly, the crack formation in the oxide layer tends to decrease as the MoSi2 concentration increases. In addition, it is noteworthy that as sintered compact, the WC-12Co becomes lighter but harder with the addition of MoSi2. •As the MoSi2 content increases, the WC-12Co forms new phases such as Co3Mo3C, WSi2, and Mo2C.•At 700 °C, 10 and 15 wt% MoSi2 addition leads to a significant decrease in oxidation resistance forming a thicker oxide layer.•The oxide layer formed consists mainly of a mixture of CoWO4 and WO3 scales whose fraction depends on the MoSi2 content.•Interestingly, the crack formed in the oxide layer tends to decrease with the increase of MoSi2 concentration.•Moreover, as a sintered compact, WC-12Co becomes lighter but harder with the addition of MoSi2.