Stress corrosion cracking behavior and mechanism of aging treated Monel K500 alloy in flowing seawater

Monel K500 alloy is widely used in sea engineering and suffers the failure risk of flowing seawater under load. Therefore, the stress corrosion cracking (SCC) and flow accelerated stress corrosion cracking (FA-SCC) behavior and mechanism of aged Monel K500 alloy were investigated. Results showed that TiCN particles were observed in alloys, and the number and size of γ′ phase in Monel K500 alloy gradually increased as the aging temperature increased, while γ′ phase was not found in solution treated alloy. The yield strength of Monel K500 alloy after heat treatment and SCC experimentation was, from high to low, in the order of the ones aged at 630 °C, 700 °C, 560 °C, and solution treated. The corrosion resistance of Monel K500 alloy from high to low during SCC and FA-SCC experiments is in the order of alloys aged at 560 °C, 700 °C, 630 °C, and solution treated. Pit corrosion was found at the matrix adjacent to TiCN particles, and cracks were mainly observed at grain boundaries (GBs) after SCC and FA-SCC experiments and after tensile testing. Generally, the SCC of alloys was caused by the synergistic effect of the anodic dissolution at exposed metal matrix and the pit corrosion of metal matrix adjacent to TiCN particles, which was further accelerated by flowing.