Effects of constant load on corrosion cracking of 304 ASS at 600°C in molten salts

The effects of constant load (CL) on corrosion cracking of 304 austenitic stainless steel (ASS) in molten salts (binary nitrate salts, 60 wt% NaNO₃, and 40 wt% KNO₃) were investigated. A pair of novel clamping fixture was designed to fix the tensile sample, making the gauge section immersed in molten salts. The CL tensile tests were applied with the initial stress of 212 MPa and the temperature of 600°C. Optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy were employed to characterize the deformation behavior and corrosion features. The results show that corrosion of 304 ASS in molten salts was aggravated by the continuous deformation due to the cracking of protective oxide scale. Grain boundaries were oxidized and weakened by the molten salt, leading to a crack propagating. Compared with the creep test result, a reduced rupture life of 304 ASS under constant loading in molten salts was observed.