Microstructure and wear resistance of in-situ TiN/(Nb, Ti)5Si3 reinforced MoNbTaWTi-based refractory high entropy alloy composite coatings by laser cladding

MoNbTaW Refractory High Entropy Alloy (RHEA) coating has caught the extensive interest of researchers due to its simple body-centered cubic structure and excellent room temperature plasticity. However, it is difficult to prepare refractory high-entropy alloy coatings by laser melting due to its high melting point. In this study, MoNbTaWTi (Si3N4) x: (weight ratio; x = 0.5, 1.0, 1.5 and 2.0) RHEA composite coatings were fabricated by laser cladding on the Ti-6Al-4V alloy. The experimental results show that laser cladding may produce TiN/(Nb, Ti)5Si3 ceramic particles and BCC phases in- situ in the coating when nano-Si3N4 is added. Moreover, the in-situ reaction between element Ti and element N in the molten pool can be release a large amount of heat, which can efficiently facilitate the synthesis of RHEA coating. The in-situ generated TiN/(Nb, Ti)5Si3 ceramic particles significantly increase the hardness and wear resistance of the composite coatings. The influence of the content of Si3N4 on the ceramic morphology, microstructure, microhardness, and tribology of RHEA coatings was comprehensively evaluated.