Microstructure and high-temperature compression performance of the hydrogenated titanium alloy welded joint

Titanium alloy blades repaired by welding in aero-derivative gas turbines often suffer from hydrogen embrittlement damage during service in hydrogen containing environments. The microstructure, Vickers hardness and hydrogen action mechanism, high-temperature compression performance of titanium alloy argon arc welded joints with different hydrogen content were studied in detail. The results show that large lamellar of δ hydride precipitated from the 0.12% H welded joint, with the increase of hydrogen content, the size of the hydride increased, and the microstructure of base metal, heat affected zone and weld zone evolved significantly. The hardness value of the 0.21% H was significantly higher than that of other hydrogen levels, and high hydrogen enhanced the hardness of the welded joint. The H solid solution strengthening effect at low hydrogen levels slightly increased the hardness of α grains. The precipitation of hydrides at high hydrogen levels was accompanied by lattice volume expansion, which caused local plastic deformation of the metal and subsequently generated a large number of dislocations. The movement of dislocations required winding or cutting through hydrides, which caused a significant increase in the hardness of α grains. The amount of compression had limited influence on the high-temperature compression rheological stress, and the recrystallization softening effect was mainly controlled by the deformation temperature. As the amount of compression increased, the α grains along with hydrides were elongated along the vertical compression direction or bent at a certain angle with the compression direction. The hydride grew along the grain boundaries of lamellar α, and the phenomenon of tissue recrystallization was not obvious during hot compression.