Solidification characteristics and microstructure of TaNbZrTi refractory high entropy coating by extreme high-speed laser cladding

• Published in: International journal of refractory metals & hard materials Vol. 115; p. 106257
• Main Authors: Zhou, Jia-li, Cheng, Yan-hai, Wan, Yi-xing, Wang, Yun-fei, Chen, Yong-xiong, Liang, Xiu-bing
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.09.2023
• Subjects: Dynamic solidification; Extreme high-speed laser cladding; Microstructure; Molten pool simulation; Refractory high entropy alloy; Molten pool simulation; Dynamic solidification; Microstructure; Refractory high entropy alloy; Extreme high-speed laser cladding
• ISSN: 0263-4368; 2213-3917
• DOI: 10.1016/j.ijrmhm.2023.106257

Extreme high-speed laser cladding (EHLC) has shown potential in producing refractory high entropy alloy (RHEA) coatings with excellent forming quality. However, there is a lack of theoretical guidance for the EHLC process, and the traditional heat source model is unsuitable. In this study, the laser-molten metal composite heat source model was improved based on the characteristics of EHLC, and a temperature field model suitable for EHLC tubular matrix surface was established and verified by infrared thermal imaging. The solidification characteristics and microstructure of TaNbZrTi RHEA coating prepared by laser cladding (LC), high-speed laser cladding (HLC), and EHLC were compared through temperature field simulation and experimental characterization. The results indicate that the cooling rate of molten pool increases significantly with the increase of scanning speed. EHLC coating has higher cladding efficiency, lower heat accumulation and dilution rate, and denser grain structure compared to LC and HLC coatings. TaNbZrTi coating exhibits a BCC1 + BCC2 phase structure, and the hardness of LC, HLC, and EHLC coating is 577.5, 487.8, and 545.2 HV0.3, respectively. This study provides a simulation model and process guidance for the preparation of TaNbZrTi RHEA coatings. •The temperature field model of EHLC was established by improving the laser-molten metal composite heat source model.•With the increase of scanning speed, G × R increases significantly, and the EHLC has a denser grain structure.•With the rapid decrease of G/R, the grains transform into plane grains → columnar grains → dendrites → cellular grains.•Due to the diffusion of substrate elements, eutectic structure is formed at the coating-substrate binding region.