Improved high-temperature hardness and wear resistance of Inconel 625 coatings fabricated by laser cladding

Abstract

In this study, Inconel 625 coatings were fabricated by laser cladding and shielded metal arc welding, and the microstructure, hardness and wear resistance at both room and elevated temperatures are investigated. The results indicate that laser cladded Inconel 625 coating has finer microstructure, alleviated segregation of Mo and Nb and lower dilution of iron compared with arc welded one as revealed by XRD, SEM and EDS results. The hardness profile at room temperature can be divided into four regions, namely coating zone, iron dilution zone, heat affected zone and substrate. Laser cladded Inconel 625 coating has slightly higher hardness in coating zone, whereas much higher hardness in iron dilution zone, indicating that iron distribution plays important role in the hardness. At elevated temperatures, the hardness of laser cladded Inconel 625 coating is higher due to finer microstructure and alleviated segregation. The wear test results show that abrasive wear is apparent at room temperature, whereas adhesive wear is dominant at elevated temperature. In comparison, laser cladded coating has lower wear rate because of lower dilution of iron and higher hardness. Therefore, laser cladded Inconel 625 coating is preferred due to its better mechanical performance at both room and elevated temperature.