Near-threshold fatigue crack growth behavior of 10% Cr martensitic steel welded joint with 9% Cr weld metal in high temperature air

Abstract

The near-threshold fatigue crack growth (FCG) behavior under different stress ratios (R) of a 9%–12% Cr steel welded joint was studied in 538 °C air. The most significant oxide-induced crack closure (OICC) occurred in weld metal (WM) due to the lowest Cr content, resulting in the highest threshold value (ΔKth) of WM. The base metal (BM) with coarser grains and denser lath structures had more obvious roughness-induced crack closure (RICC) and more severe crack deflection, which led to a higher ΔKth of BM than heat affected zone (HAZ). The ΔKth of WM, HAZ and BM decreased as R increased.