Mechanical properties and corrosion resistance of TC4 titanium alloy joints by plasma arc welding plus 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 beta/alpha phase volume ratio, small grain size, and HAGB content.