In-situ observations of melt degassing and hydrogen removal enhanced by ultrasonics in underwater wet welding

• Published in: Materials & design Vol. 188; p. 108482
• Main Authors: Chen, Hao, Guo, Ning, Xu, Kexin, Xu, Changsheng, Zhou, Li, Wang, Guodong
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.03.2020; Elsevier
• Subjects: Diffusible hydrogen; In-situ X-ray imaging; Solidification; Ultrasonic melt processing; Underwater welding; In-situ X-ray imaging; Diffusible hydrogen; Underwater welding; Ultrasonic melt processing; Solidification
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2020.108482

In this study, the phenomenon of gas removal behaviors in the melt pool and the flow behaviors of melt pool were observed using an in-situ X-ray imaging method. Based on the ultrasonic effects, a novel processing method was developed to reduce porosity and decrease diffusible hydrogen content in the deposited metal. The effects of ultrasonic output power on the size and frequency of gas bubble collapsing were studied. Results showed that with the assistance of ultrasonic, the gas bubble size were smaller and the collapsing frequency was significantly increased. The porosity decreased from 1.4% to 0.5% and the hydrogen diffusible content decreased from 24.5 to 18.6 ml/100 g when the ultrasonic power increased to 720 W. The possible hydrogen removal mechanism was proposed by two aspects including the microcosmic and macrocosmic scale. [Display omitted] •Melt degassing phenomenon enhanced by ultrasound is studied by an in-situ imaging method.•Effects of ultrasonic power on weld porosity and diffusible hydrogen content are investigated•Appropriate ultrasonic power decreases the porosity and diffusible hydrogen content in the welds.•Mechanism of ultrasonic degassing and diffusible hydrogen decreasing are discussed.