Microstructure evolution and nucleation mechanism of Inconel 601H alloy welds by vibration-assisted GTAW
来源期刊:International Journal of Minerals Metallurgy and Materials2018年第7期
论文作者:Ze-long Wang Zhen-tai Zheng Li-bing Zhao Yun-feng Lei Kun Yang
文章页码:788 - 799
摘 要:Nickel-based alloys exhibit excellent high-temperature strength and oxidation resistance; however, because of coarse grains and severe segregation in their welding joints, these alloys exhibit increased susceptibility to hot cracking. In this paper, to improve the hot-cracking resistance and mechanical properties of nickel-based alloy welded joints, sodium thiosulfate was used to simulate crystallization, enabling the nucleation mechanism under mechanical vibration to be investigated. On the basis of the results, the grain refinement mechanism during the gas tungsten arc welding(GTAW) of Inconel 601 H alloy under various vibration modes and parameters was investigated. Compared with the GTAW process, the low-frequency mechanical vibration processes resulted in substantial grain refinement effects in the welds; thus, a higher hardness distribution was also achieved under the vibration conditions. In addition, the γ′ phase exhibited a dispersed distribution and segregation was improved in the welded joints with vibration assistance. The results demonstrated that the generation of free crystals caused by vibration in the nucleation stage was the main mechanism of grain refinement. Also, fine equiaxed grains and a dispersed γ′ phase were found to improve the grain-boundary strength and reduce the segregation, contributing to preventing the initiation of welding hot cracking in nickel-based alloys.
Ze-long Wang1,Zhen-tai Zheng1,Li-bing Zhao1,Yun-feng Lei1,Kun Yang2
1. School of Materials Science and Engineering, Hebei University of Technology2. Beiyang Chemical Equipment of Tianjin University Co., Ltd.
摘 要:Nickel-based alloys exhibit excellent high-temperature strength and oxidation resistance; however, because of coarse grains and severe segregation in their welding joints, these alloys exhibit increased susceptibility to hot cracking. In this paper, to improve the hot-cracking resistance and mechanical properties of nickel-based alloy welded joints, sodium thiosulfate was used to simulate crystallization, enabling the nucleation mechanism under mechanical vibration to be investigated. On the basis of the results, the grain refinement mechanism during the gas tungsten arc welding(GTAW) of Inconel 601 H alloy under various vibration modes and parameters was investigated. Compared with the GTAW process, the low-frequency mechanical vibration processes resulted in substantial grain refinement effects in the welds; thus, a higher hardness distribution was also achieved under the vibration conditions. In addition, the γ′ phase exhibited a dispersed distribution and segregation was improved in the welded joints with vibration assistance. The results demonstrated that the generation of free crystals caused by vibration in the nucleation stage was the main mechanism of grain refinement. Also, fine equiaxed grains and a dispersed γ′ phase were found to improve the grain-boundary strength and reduce the segregation, contributing to preventing the initiation of welding hot cracking in nickel-based alloys.
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