Underwater Laser Welding of Pure Ti: Oxidation and Hardening Behaviors
Abstract
:1. Introduction
2. Materials and Methods
3. Results and Discussion
3.1. Macro-Morphology
3.2. Microstructure
3.3. Oxidation Behavior of Underwater Weld
3.4. Hardening Behavior of Underwater Welds
4. Conclusions
- (1)
- The weld morphology of underwater local dry laser welding is smooth and slightly oxidized, which is better than that of underwater wet welding. With the increase of welding speed, the oxidation degree of the surface of the weld decreases due to the decrease of local energy input.
- (2)
- Compared with a weld with the same process parameters in atmosphere, the cross-section geometric morphology was almost unaffected by the special underwater welding environment. The variation law of the cross-section morphology was the same as that in ordinary atmosphere laser welding.
- (3)
- The weld of underwater local dry laser welding presents a three-layer structure of an oxide layer, an oxygen-enriched area, and an oxidation free area. High temperature and high pressure water vapor and local blowing are the direct causes of weld oxidation, and the porosity defects further aggravate the oxidation behavior. Reducing the heat input and adjusting the blowing direction of the assisting gas may reduce the weld oxidation.
- (4)
- The water environment will affect the solid-state phase transformation process, accelerate the cooling of the molten pool, and form fine acicular martensite. It will increase the overall microhardness of the weld in water. In addition, the oxygen enriched ambience is the cause of the increase in local microhardness.
- (5)
- With the increase of welding speed, the microhardness of a weld in water decreases. When the welding speed was increased to 3 m/min, the microhardness of the weld was almost the same as that in the atmospheric environment. In this way, local dry underwater laser welding with air assistance is a cost-effective method, which is promising for the in situ repair of large-scale underwater facilities.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Process No. | Power P (kW) | Welding Speed v (m/min) | Raw Water Depth D (mm) | Welding Environment |
---|---|---|---|---|
1 | 3 | 1.0 | 0 | Atmosphere |
2 | 3 | 1.0 | 2 | Local dry |
3 | 3 | 1.5 | 2 | Local dry |
4 | 3 | 2.0 | 2 | Local dry |
5 | 3 | 2.5 | 2 | Local dry |
6 | 3 | 3.0 | 2 | Local dry |
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Luo, M.; Wei, P.; Li, Q.; Hu, R.; Huang, A.; Pang, S. Underwater Laser Welding of Pure Ti: Oxidation and Hardening Behaviors. Metals 2021, 11, 610. https://doi.org/10.3390/met11040610
Luo M, Wei P, Li Q, Hu R, Huang A, Pang S. Underwater Laser Welding of Pure Ti: Oxidation and Hardening Behaviors. Metals. 2021; 11(4):610. https://doi.org/10.3390/met11040610
Chicago/Turabian StyleLuo, Manlelan, Pengyu Wei, Quanhong Li, Renzhi Hu, Anguo Huang, and Shengyong Pang. 2021. "Underwater Laser Welding of Pure Ti: Oxidation and Hardening Behaviors" Metals 11, no. 4: 610. https://doi.org/10.3390/met11040610