SEM, TEM and X-ray diffraction methods were used to observe and analyze the microstructure, phase distribution and composition distribution of Cu and Mo-containing (Ni-A) and Cu and Mo-free (Ni-B) Ni-based alloy spray-welding coatings. The micro-Vickers hardness of the matrix and the heat-effected, combined and coating areas was measured. The thermal fatigue process was actualized by an induction heater to investigate the phase morphology and composition distribution and the phenomenon of thermal cracks appearing and spreading. Experimental results show that there exists needle Cr-rich phase with excellent thermal fatigue property in both Ni-A and Ni-B coatings. Ni-A coating can be divided into two areas:one is round-shaped Cr-rich phase which distributes near the matrix uniformly and the other is needle-shaped Cr-rich phase which distributes near the surface with a distance of about 200μm away from the outer surface of the coating. The volume of the needle-shaped Cr-rich phase is smaller than that of the roundshaped Cr-rich phase by several ten times. Compared with Ni-A coating, Ni-B coating has only needle-shaped Cr rich phase distributing in the spray coating uniformly. The thermal fatigue property of Ni-A coating is better than that of Ni-B because of a transition area in Ni-A coating. The results obtained by EDS analysis show that there is almost no diffusion of elements in Ni-A and Ni-B coatings during the thermal experiment and the two types of coatings have excellent thermal stability.
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