Effect of Si Addition on Tribological Properties of NbTaWMo Refractory High Entropy Alloy at High Temperature

In this study, NbTaWMo high entropy alloy with Si addition were produced by spark plasma sintering. The phase constitutions, microstructures and mechanical properties were analyzed, and the tribological properties from 25 ℃ to 800 ℃ were investigated. NbTaWMo refractory high entropy alloys were composed of BCC phase, and NbTaWMoSi_0.25 refractory high entropy alloys were composed of BCC and silicide phases. As Si was added in NbTaWMo refractory high entropy alloy, the yield strength, compressive strength and fracture strain at room temperature improved significantly. The friction coefficients of NbTaWMo and NbTaWMoSi_0.25 alloys were comparable. However, the wear rates decreased significantly as Si was added in NbTaWMo high entropy alloy. The wear mechanism of NbTaWMoSi_0.25 alloys was abrasive wear at low and medium temperatures. At high temperatures, the main wear mechanisms were abrasive wear and oxidation wear. NbTaWMoSi_0.25 refractory high entropy alloy had excellent wear resistance at a wide range temperatures. Therefore, NbTaWMoSi_0.25 refractory high entropy alloy had great potential for tribological applications at high temperature.