Effect of heat and cryogenic treatments on the microstructure and properties of YF3 modified NiTi-Si laser cladding coatings

YF 3 modification NiTi-Si coatings were prepared on Ti-6Al-4 V substrate by laser cladding. On this foundation, heat and cryogenic treatments were conducted respectively to explore the effect of after-treatment procedures. The consequence of post-treatment methods on the phase constituent, microstructure, mechanical property, and phase transition characteristics of post-treatment coatings was studied. The phase constituent of the three coatings was roughly the same, composed of NiTi and NiTi 2 . The results show that heat treatment led to the coarsening of NiTi phase grain size and increased Si content in the NiTi 2 phase. In addition, due to the rapid cooling rate provided by cryogenic treatment, the spinodal decomposition of the Si element occurred in the NiTi 2 phase. Furthermore, the post-treatments also affected the phase transformation characteristics of the coatings. As the temperature of martensitic transformation is sensitive to the content of Ni element in the NiTi phase, the M s and M f points of the heat treatment coating were slightly higher. In contrast to the heat treatment, the M s and M f points of the cryogenic treatment coating decreased. The microhardness of the three coatings is as follows: cryogenic treatment > original coatings > heat treatment. The cryogenic treatment coating has the highest microhardness due to grain refinement and spinodal decomposition. In addition, the cryogenic treatment coating showed the best wear morphology.