Corrosion Resistance of the Welded Joints from the Ultrafine-Grained Near-α Titanium Alloys Ti-5Al-2V Obtained by Spark Plasma Sintering

A solid-phase diffusion welding of coarse-grained and ultrafine-grained (UFG) specimens of titanium near-alpha alloy Ti-5Al-2V used in nuclear power engineering was made by Spark Plasma Sintering. The failure of the welded specimens in the conditions of hot salt corrosion and electrochemical corrosion was shown to have a preferentially intercrystalline character. In the case of the presence of macrodefects, crevice corrosion of the welded joints was observed. The resistance of the alloys against the intercrystalline corrosion was found to be determined by the concentration of vanadium at the titanium grain boundaries, by the size and volume fraction of the beta-phase particles, and by the presence of micro- and macropores in the welded joints. The specimens of the welded joints of the UFG alloy are harder and have a higher resistance to hot salt corrosion and electrochemical corrosion.

Automated summary

A solid-phase diffusion welding process using Spark Plasma Sintering was used to join coarse-grained and ultrafine-grained specimens of Ti-5Al-2V titanium alloy in nuclear power engineering. The failure of the welded specimens was mainly due to intercrystalline corrosion under hot salt corrosion and electrochemical corrosion conditions. The presence of macrodefects led to crevice corrosion in the welded joints. The resistance to intercrystalline corrosion was influenced by the vanadium concentration at grain boundaries, the size and volume fraction of beta-phase particles, and the presence of micro- and macropores in the welded joints. The UFG alloy welded joints exhibited higher hardness and better resistance to hot salt corrosion and electrochemical corrosion.