Effects of post-weld heat treatment on the microstructure and mechanical properties of laser-welded NiTi/304SS joint with Ni filler

By Yuhua Chen, Song-lin Sun, Timing Zhang, Xingwen Zhou, Shuhan Li. Materials Science & Engineering: A, 2020

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Abstract Adding Ni as filler material is one of the effective methods to restrain the cracks in laser-welded joints of NiTi/stainless steel (SS), while the formation of Ni3Ti at the NiTi/Ni interface result in uneven distribution of the microstructure of the joint, which limits tensile strength of the joint. In this study, post-weld heat treatment (PWHT) at 650 °C and 850 °C were applied on a defect-free NiTi/Ni/SS joint to improve its mechanical properties. As the PWHT temperature increases, more Ni3Ti was observed at the weld metal. This precipitation strengthened the weld metal, resulting in the average hardness of the weld metal increased from 375 HV0.2 to 493 HV0.2. Owing to the homogenization of microstructure of joints after PWHT, the tensile strength of the joint improved. The highest joint average strength reached 643 MPa at 850 °C PWHT, which is about 2.12 times higher than that of the as-welded joint.

Subfields: Materials Chemistry, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/b637fda3d3a0fa6ed4844bb5e7e9d95d20b9d3d9