Study on the Effect of Ni Addition on the Microstructure and Properties of NiTi Alloy Coating on AISI 316 L Prepared by Laser Cladding

Yuqiang Feng; Zexu Du; Zhengfei Hu

doi:10.3390/ma14164373

Study on the Effect of Ni Addition on the Microstructure and Properties of NiTi Alloy Coating on AISI 316 L Prepared by Laser Cladding

Materials (Basel). 2021 Aug 4;14(16):4373. doi: 10.3390/ma14164373.

Authors

Yuqiang Feng¹, Zexu Du¹, Zhengfei Hu¹

Affiliation

¹ Shanghai Key Laboratory for R&D and Application of Metallic Functional Materials, School of Materials Science and Engineering, Tongji University, Shanghai 201804, China.

Abstract

This paper investigated 55 NiTi commercial alloy powder and 55 NiTi with 5% pure Ni mixed powder (55 NiTi + 5 Ni) coatings fabricated by laser cladding to study the effect of extra Ni addition on the microstructure and properties of the coating. The XRD and EDS results show that the major phases in the coatings were NiTi and Ni₃Ti. Besides that, a second phase like Ni₄Ti₃, Fe₂Ti, and NiTi₂ was also detected, among which, NiTi₂ was only found in 55 NiTi coating. The proportion of the phase composition in the coating was calculated via the software Image-Pro Plus. The hardness of the cladding layer reaches 770-830 HV, which was almost four times harder than the substrate, and the hardness of 55 NiTi + 5 Ni coating was around 8% higher than that of 55 NiTi coating. The wear resistance of the 55 NiTi + 5 Ni coating was also better; the wear mass loss decreased by about 13% and with a smaller friction coefficient compared with the 55 NiTi coating. These results are attributed to the solid solution strengthening effect caused by Ni addition and the second phase strengthening effect caused by the content increase of the Ni₃Ti phase in the cladding layer.

Keywords: NiTi alloy; laser cladding; microstructure; wear.