Effect of heat treatment on microstructure and residual stress of wire arc sprayed high carbon steel coating

The 0.8% carbon steel wire was used to deposit coating, and the coated samples were annealed at 550, 650 and 800 degrees C respectively, which were then quenched in water. The microstructure, phase composition and residual stress of the heat treated coatings were studied and compared with that of the coating without any post-treatment. Results show that the heat treatment processes have significant influences on coating oxide, steel alloy grains and residual stresses. The high carbon steel coating expressed tensile stress after spraying, but when the special quenching process was applied, martensite and bainite were formed in the coating, resulting in expansion of material volume, which made the residual stress of the coating change from tension to compression. The correlation between the microstructure and residual stress strongly informed that phase transformation in the coating should be carefully controlled if spray forming thick coating is aimed.