Effect of oxygen contents in shielding gas on GTAW joints of commercially pure titanium

This work investigates the impact of oxygen content in shielding gas on GTAW joints of commercially pure titanium. Commercially pure titanium GTAW welds exhibit unique color characteristics, with silver, straw, and white/grey indicating varying degrees of quality. The study finds that a 100% argon shielding gas results in silver-colored, acceptable welds. However, increasing oxygen content of shielding gas leads to color changes, indicating oxidation and potential defects. Liquid penetrant testing confirms that higher oxygen levels in the shielding gas can result in cracks and reduced quality. Microstructure analysis reveals the thickening of surface oxide layers with increased oxygen content. XRD analysis identifies oxide phases, such as Ti ₆ O and TiO ₂ . Weld penetration remains consistent, but oxygen-rich environments lead to narrower melt pools and irregular bead shapes. Microstructural analysis shows the formation of beta-Ti phases and subgrains in the fusion zone, influenced by oxygen content. Oxygen concentration analysis corroborates the presence of oxygen-induced beta-Ti phases. Hardness increases with higher oxygen content due to precipitation and subgrain formation. Subgrain formation is attributed to residual stresses during welding. Overall, maintaining oxygen content below 5% in the shielding gas during GTAW welding of pure titanium positively affects weld hardness.