Abstract
Underwater laser beam welding (ULBW) with filler wire was applied to Ti-6Al-4V alloy. Process parameters including the back shielding gas flow rate (BSGFR) (the amount of protective gas flowing over the back of the workpiece per unit time), focal position, and laser power were investigated to obtain a high-quality butt joint. The results showed that the increase of BSGFR could obtain the slighter oxidation level and refiner crystal grain in the welded metals. Whereas the back shielding gas at a flow rate of 35 L/min resulting in pores in the welded metals. With the increasing of the heat input, the welded metals went through three stages, i.e., not full penetration, crystal grain refinement, and coarseness. Crystal grain refinement could improve the mechanical properties, however, not full penetration and pores led to the decline in mechanical properties. Under optimal process parameters, the microstructure in the fusion zones of the underwater and in-air weld metals was acicular martensite. The near the fusion zone of the underwater and in-air weld metals consisted of the α + α′ phase, but almost without the α′ phase in the near base metal zone. The tensile strength and impact toughness of the underwater welded joints were 852.81 MPa and 39.07 J/cm2, respectively, which approached to those of the in-air welded joints (861.32 MPa and 38.99 J/cm2).
Highlights
Titanium and its alloys have many advantages, such as high specific strength, outstanding corrosion resistance, and superior biocompatibility, so they are extensively applied to aerospace field, ocean engineering, and biomedical devices
Underwater welding (UW) turns into the dominating means of maintenance, which was used in offshore pipelines and platforms, vessels, seashore components, as well as port equipment and systems [4]
underwater dry welding (UDW) is usually implemented in an underwater high-pressure chamber and can obtain high-quality welded joints, but in comparison to underwater wet welding (UWW), the welding equipment of UDW is complex and expensive, extremely [6]
Summary
Titanium and its alloys have many advantages, such as high specific strength, outstanding corrosion resistance, and superior biocompatibility, so they are extensively applied to aerospace field, ocean engineering, and biomedical devices. Welding of Ti-6Al-4V alloy [1]. Beguin et al explored the laser welding of thin titanium sheet [2]. Chen et al carried out laser welding with filler wire of Ti-alloy [3]. Underwater welding (UW) turns into the dominating means of maintenance, which was used in offshore pipelines and platforms, vessels, seashore components, as well as port equipment and systems [4]. UDW is usually implemented in an underwater high-pressure chamber and can obtain high-quality welded joints, but in comparison to UWW, the welding equipment of UDW is complex and expensive, extremely [6]. UWW technology is generally employed [7]
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