Threshold value ($\mathrm{\Delta }{K}_{\mathit{th}}$) and fatigue crack growth behavior at different temperatures and stress ratios were investigated in weld metal (WM) and heat-affected zone (HAZ) of an ex-service CrMoV steel joint. Compared with the $\mathrm{\Delta }{K}_{\mathit{th}}$ at 25 ℃, the $\mathrm{\Delta }{K}_{\mathit{th}}$ at 500 ℃ and 540 ℃ were still high, because significant oxide-induced crack closure (OICC) occurred in WM and HAZ during high-temperature tests. The high-temperature $\mathrm{\Delta }{K}_{\mathit{th}}$ of HAZ were higher than those of WM, due to their more severe oxidation and more significant OICC. This was owing to the lower Si and Cr content and smaller grain size in HAZ.

中文翻译：

---

退役 CrMoV 钢接头焊缝金属和热影响区的近阈值疲劳裂纹扩展行为

阈值 ($\mathrm{\Delta }{ķ}_{\mathit{th}}$) 以及不同温度和应力比下的疲劳裂纹扩展行为在退役 CrMoV 钢接头的焊缝金属 (WM) 和热影响区 (HAZ) 中进行了研究。与$\mathrm{\Delta }{ķ}_{\mathit{th}}$在 25 ℃ 时，$\mathrm{\Delta }{ķ}_{\mathit{th}}$在 500 ℃ 和 540 ℃ 时仍然很高，因为在高温试验期间 WM 和 HAZ 发生了显着的氧化物诱导裂纹闭合 (OICC)。高温$\mathrm{\Delta }{ķ}_{\mathit{th}}$HAZ 比 WM 高，因为它们的氧化更严重，OICC 更显着。这是由于 HAZ 中较低的 Si 和 Cr 含量以及较小的晶粒尺寸。