Corrosion Fatigue Crack Propagation Mechanism of High-Strength Steel Bar in Various Environments

This paper investigated the corrosion fatigue crack propagation mechanism of high-strength steel bar HRB400 in various corrosive environments. Fatigue crack growth (FCG) tests were conducted under different fatigue loading types, environments, and stress ratios. The fatigue loading type included the constant and stepwise decreasing load amplitude. The environments were air, distilled water, 3.5% NaCl solution, and an artificially accelerated corrosive environment. The stress ratio ranged from 0.1 to 0.7. The threshold stress-intensity factor range and FCG rate under various test conditions were obtained. The FCG path and fracture morphology were examined by optical microscopy and scanning electron microscopy, respectively. The threshold stress-intensity factor ranges, FCG rates, FCG paths, and fracture features under different conditions were compared. The corrosion fatigue mechanism of the steel bar under the test environments were quantitatively analyzed. The results showed that hydrogen embrittlement played a predominant role in the corrosion fatigue process of the HRB400 steel bar. The contribution of anodic dissolution to the FCG rate increased as the aggressiveness level increased. The contribution of hydrogen embrittlement to the FCG rate increased with the increase of stress ratio and stress-intensity factor range.