Analysis of Electrode Tip Angle Variation on Weld Geometry, Distortion, and Hardness in Commercially Pure Titanium Welded Using Pulsed-Gas Tungsten Arc Welding

Abstract

Gas tungsten arc welding (GTAW) and its variants are esteemed as economically efficient welding methods for welding titanium alloys in the aerospace and nuclear industries. In the present work, the influence of electrode tip angle on weld geometrical elements, distortion, and hardness was investigated in commercially pure titanium (CP-Ti) sheets welded through pulsed-GTAW. Bead-on-plate (BOP) welding was performed on 2 mm thick CP-Ti sheets using electrode tip angles of 30, 45, 60, 75, and 90°. Defect-free welds were obtained by utilizing an indigenously developed shielding setup assembled with p-GTAW machine. The weld geometrical elements were evaluated using metallographic samples of weldment cross section under the stereomicroscope. The findings revealed that as the electrode tip angle increased from 30 to 60°, weld bead width decreased from 6.84 to 5.32 mm. Additionally, the weld penetration initially increased from 1.59 to 1.75 mm up to 60°, but subsequently decreased to 1.51 mm at 90°. Furthermore, increasing the electrode tip angle led to reduction in weld distortion. Microhardness measurements demonstrated an increase in hardness from the base (141 HV_0.2) to the weld region (151 HV_0.2), with a slight decrease observed in the HAZ (134 HV_0.2). This hardness trend across the weldment remained consistent with each electrode tip angle, and higher hardness was observed using large electrode tip angle.