Hot corrosion behavior of three different zones of linear friction welded Ti‐22Al‐25Nb alloy

Abstract

Ti‐22Al‐25Nb joint was achieved by using linear friction welding (LFW) technique. The hot corrosion behavior of base metal, weld zone, and thermo‐mechanically affected zone (TMAZ) was investigated at 700 °C in 25% NaCl‐75% Na2SO4 (wt%) mixed molten salt. In the initial stage, the base metal and joint exhibit similar oxidation resistant ability, and the corrosion products formed on all zones are mainly composed of TiO2, Nb2O5, and Al2O3. The formation of NaNbO3 first occurs in base metal and TMAZ after 50 h, while the weld zone is free of NaNbO3 until 100 h. The development of pitting corrosion in both base metal and TMAZ is caused by the diffusion of sulfur and re‐oxidation of sulfides. After a prolong exposure in molten salts, more serious sulfuration, acid dissolution, and escape of gaseous chlorides occurred in base metal leading to a drastic acceleration of corrosion rate.

Why do cracks occur in the weld joint of Ti-22Al-25Nb alloy during post-weld heat treatment?

“…In some cases, Ti-22Al-25Nb alloy, like any structural material, must be welded to fabricate components with complex geometries. The joining of Ti-22Al-25Nb alloy has been conducted using various welding technologies, such as diffusion bonding welding (Zou et al, 2009;Chu et al, 2017), electron beam welding (Chen et al, 2016;Li et al, 2017), laser beam welding (Zhang et al, 2021b;Zhang et al, 2021c), and friction welding (Chen et al, 2018;Zhao et al, 2020). The main shortcomings of these Ti-22Al-25Nb alloy welding methods are their high cost and limited versatility.…”

Oxidative Corrosion Mechanism of Ti2AlNb-Based Alloys during Alternate High Temperature-Salt Spray Exposure

“…In recent years, a series of studies have been carried out at home and abroad on the various properties of Ti 2 AlNb alloys [15,[18][19][20][21][22]. He et al [18] investigated the oxidation behaviour of a novel-element alloyed Ti 2 AlNb-based alloy in the temperature range of 650-850 • C. It has been demonstrated that the oxidation rate and mass gain of the Ti 2 AlNb alloy becomes progressively greater with increasing temperature.…”