Corrosion fatigue behaviors of HSB800 and its HAZs in air and seawater environments

Corrosion fatigue behaviors of high-performance steel, HSB800, and its heat-affected zones (HAZs) were investigated in air and seawater environments through uniaxial tension-compression fatigue tests. Three types of material including the as-received base metal (BM), coarse-grained (CG) HAZ, and inter-critically reheated coarse-grained (ICCG) HAZ of HSB800 were used. A 3.5% sodium chloride solution was used as a seawater environment. A 600–940 MPa maximum stress was applied during the fatigue load cycles, and the minimum stress was set to zero. The test results show that the ICCG HAZ had much less fatigue resistance than the BM and CG HAZ in both air and seawater environments. The deterioration mechanisms of the corrosion fatigue behaviors based on the microstructural aspects were also discussed. In addition, an empirical model for estimating corrosion fatigue life was developed by considering the stress sensitivity of loading conditions. Subsequently, material parameters in the power-law relationship between applied stress amplitude and cycles-to-failure were characterized. The ICCG HAZ exhibited more sensitivity on the stress level of the corrosion fatigue life than on those of the BM and CG HAZ. Meanwhile, the amount of environmental degradation of fatigue life of BM from in-air to in-seawater condition was greater than the others because of its microstructure with relatively adequate potential to corrode.