Mechanical properties and corrosion resistance of TC4 titanium alloy joints by plasma arc welding + gas tungsten arc welding combination welding

In this paper, plasma arc welding (PAW) and plasma arc welding combined with gas tungsten arc welding (PAW + GTAW) were used to weld TC4 titanium alloy plate (thickness of 8 mm). The relationship between mechanical properties, corrosion resistance, phase composition, and microstructure of PAW welded joint (P) and PAW + GTAW welded joint (P + G) was compared. Tensile test and microhardness results show that P + G welded joints exhibit superior mechanical properties compared to P welded joints. The polarization curves and EIS results of both P and P + G samples were compared. The surface morphology of the samples was evaluated, and the potential corrosion mechanism of P and P + G samples was provided. The research results reveal that the PAW + GTAW welding has positively affected the corrosion performance of TC4 alloy welded joints. The improved corrosion resistance of welded joints is associated with a low β/α phase volume ratio, small grain size, and HAGB content.