Microstructure, high temperature wear resistance and corrosion behaviour of NiCrCoNbMox high-entropy alloy coatings on 15CrMoG alloy by laser cladding

The waste incineration results in the emission of a substantial amount of high-temperature corrosive atmosphere and particles, requiring stringently high-temperature corrosion and abrasion resistance on the heating surfaces of water-wall tubes in boilers. In order to improve the service life of the water-cooled wall tubes, NiCrCoNbMox coating was laser-cladded on 15CrMoG alloy. The microstructure and phase are investigated, microhardness, wear and salt corrosion resistance at 500℃ are tested, the mechanism are discussed. NiCrCoNbMox coating exhibits a dendritic (Nb, Mo)-rich Laves phase and a (Nb, Mo)-poor FCC phase. With the increase of Mo content, the Laves phases are refined. When x=1.5, the coating grains are effectively refined and uniformly distributed. The NiCrCoNbMox coating microhardness is 550~620 HV0.3, two times that of the substrate. The wear rate of NiCrCoNbMo1.5 coatings is 8×10-6mm³N-¹m-¹, which exhibits 95.9% reduction compared to the substrate. NiCrCoNbMo1.5 coating shows the excellent wear resistance at 500°C. The wear mechanism is abrasive wear, oxidative wear, accompanied by slight abrasive wear. The NiCrCoNbMo1.5 coating shows the optimal resistance to high-temperature salt corrosion due to the denser oxides such as FeCr2O4, Cr2O3, MoO3, and NiO during the high-temperature salt corrosion process.