Effect of hydrogen content on cold cracks in titanium alloy welding

This work is aiming at investigation on Hydrogen impact on welded cold cracks in titanium weldments. The results indicated that when the hydrogen content in titanium alloy is below 300 ppm, the difficulty of delayed cracking in welded joints is relatively high. With the increase of hydrogen content, the tendency of delayed cracking increases, and the fracture mode changes from ductile fracture to brittle fracture, the amount of primary α phase in the alloy decreases and eventually disappears, while the amount of β transition microstructure gradually increases with more acicular α′ phase and δ hydride. The delayed cracking at the weld toe position of the joint is related to high residual stress and the enrichment of hydrogen elements. The influence of hydrogen content on the delay of cold crack was analyzed, the mechanism of delayed cold crack generation was discussed. A model for the critical hydrogen content that causes welding cold cracks due to the coupling of welding stress and hydrogen was constructed, the coupling mechanism of welding stress and hydrogen content was clarified, and the influence of the two on the cold crack of titanium alloy welding was revealed.