• CN: 11-2187/TH
  • ISSN: 0577-6686

Journal of Mechanical Engineering ›› 2022, Vol. 58 ›› Issue (2): 176-184.doi: 10.3901/JME.2022.02.176

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Arc-fused Coating Process and Micro-joining Mechanism of NiTi Shape Memory Alloys

KE Wenchao1, CONG Baoqiang2, QI Zewu2, AO Sansan3, PANG Bowen1, GUO Wei2, PENG Bei1, CENG Zhi1   

  1. 1. School of Mechanical and Electrical Engineering, University of Electronic Science and Technology of China, Chengdu 611731;
    2. School of Mechanical Engineering and Automation, Beihang University, Beijing 100191;
    3. School of Materials Science and Engineering, Tianjin University, Tianjin 300350
  • Received:2021-05-06 Revised:2021-08-18 Online:2022-01-20 Published:2022-03-19

Abstract: NiTi Shape memory alloys (SMAs) is one of the most promising coating materials to improve the wear and oxidation resistance of the base components. In the study, the conventional direct current and ultra high-frequency pulsed (UHFP) current were respectively utilized to deposit 3-layer NiTi-coating on TA1 pure titanium substrates with tungsten inert gas welding (TIG)arc-fused coating technology. Using FLUENT software, a computational fluid dynamics (CFD) simulation model was established to analyze the coating process and micro-joining mechanism. The multiphysics, NiTi droplet transfer, Ni element transport and distribution in the micro interlayers were numerical analyzed under UHFP current compared with the direct current case. The numerical and experimental results agree well. It can be concluded that the 3-layer coatings are mainly composed of B19' NiTi martensites and NiTi2 phases, in which NiTi with nearly equal atomic ratio is dominant. The coating of the direct current case is mainly composed of coarse globular grains, while refined into smaller dendrites once UHFP current is used. In addition, the UHFP current is beneficial to the vibration of the molten pool, which promotes the uniform distribution of Ni element and effectively improves the forming quality of the coatings.

Key words: NiTi shape memory alloys (SMAs), arc-fused coating, ultra high-frequency pulsed (UHFP), computational fluid dynamics (CFD), chemical element distribution

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