Improvement of thermal shock resistance and hot mechanical properties by FCC/BCC/B2 multiphase strengthened microstructure in laser cladded high-entropy alloy coatings

Abstract

NiCoFeCrSiAlxCu0.5TiMoB0.4 high-entropy alloy (HEA) coatings were prepared by laser cladding, and the microstructure, phase structure and thermal properties were studied. The results showed that the solid solution phase of the coating matrix changed from FCC + BCC to BCC as the main phases with increasing Al content. Moreover, the enrichment of Ti resulted in the significant formation of a stacking fault structure in the interdendritic region of the dual-phase coatings. The ordered B2 phase precipitated from the BCC structure exhibited high hardness and crack damage resistance. The wear rates of the HEA-Al0.5 and HEA-Al1.5 coatings at 600 °C were 3.78 × 10−5 and 4.35 × 10−5 mm3/(N·m)−1, respectively. The wear mechanisms of HEA coatings were mainly abrasive wear and oxidation wear. Because of the high microhardness of the BCC phase, cracks initiated and propagated on the worn surface, which aggravated the oxidation wear deterioration of the HEA coating. Overall, this study may provide a theoretical basis for the microstructure-property relationships of HEA coatings and contribute to the development of high-performance coatings.