Wide-Temperature-Range Tribological Properties of In Situ Ceramic-Reinforced TaMoTiCr Refractory High-Entropy Alloy Composites

In-situ ceramic phase-reinforced TaMoTiCr refractory high-entropy alloy (RHEA) composites were prepared by spark plasma sintering with the addition of 2.5wt% and 5.0wt% h-BN, separately. Results show that the h-BN promotes the uniform formation of (Ti, Ta)N, TaB₂, and MoB ceramic phases within the body-centered cubic matrix, significantly increasing microhardness to 1136.95 HV. Tribological test results show that the composite with the addition of 2.5wt% h-BN presents great performance at room temperature with an ultra-low wear rate of 1.64×10^-7 mm³·N^-1·m^-1, while the composite with the addition of 5.0wt% h-BN shows optimal performance at 300 °C. Above 800 °C (elevated temperature condition), lubricious oxide tribolayers, rich in Cr₂O₃, TiO₂, and B₂O₃, form on the material surface, effectively reducing friction and wear. At 1000 °C, the composite with the addition of 2.5wt% h-BN achieves a wear rate of 5.22×10^-7 mm³·N^-1·m^-1. This in situ ceramic reinforcement approach effectively enhances wear resistance of RHEAs across a wide temperature range, offering great potential for advanced aerospace applications.