Analysis of microstructure, mechanical properties, and wear performance of NiTi alloy fabricated by cold metal transfer based wire arc additive manufacturing

Abstract

In this work, wall-shaped NiTi components were fabricated by cold metal transfer (CMT) based wire arc additive manufacturing (WAAM) with optimized depositing speed. The microstructure, mechanical properties, and wear performance of the as-fabricated specimens along the building direction, together with their correlations were investigated in-depth. Coarse columnar grains were refined gradually with the increase of wall height. An equiaxed microstructure was obtained in the upper region. The Ni4Ti3 precipitates were distributed in the matrix. The microhardness, critical stress, and elongation increase monotonously with the increase of wall height. Plastic deformation, together with wear-induced work hardening is the main form of wear, which is mainly hindered by the superelasticity of NiTi alloys. Good homogeneity of the microstructure, mechanical properties, and wear resistance is obtained due to the CMT process with optimized depositing speed, indicating that this technique provides great potential to make novel NiTi flexible structures.

Keywords

• NiTi alloy
• Superelasticity
• Wire arc additive manufacturing
• Cold metal transfer
• Microstructure
• Mechanical properties