Study on the effect of Cu addition on the microstructure and properties of NiTi alloy fabricated by laser cladding

Microstructure and properties of laser cladded NiTi and NiTiCu coatings were investigated to reveal the effect of Cu addition in this system. The XRD and SEM results indicated that Cu addition formed a ternary phase TiNi0.8Cu0.2, distributed in the grain boundary region of the matrix. The microhardness of NiTiCu coating was much higher than that of NiTi coating, reaching 600-700 HV. The wear resistance was improved with the friction coefficient decreased by 25.8% and the wear loss decreased by almost 50%. This was due to the grain boundary strengthening and wetting effect caused by the intergranular ternary phase and the change of the phase transformation behavior.