Abstract In the present work, fatigue crack propagation behavior of 316LN tungsten inert gas (TIG) weldment and weldment with post weld heat treatment (PWHT) was investigated at liquid helium temperature. Results indicates that the weldment with PWHT results in the highest fatigue crack propagation resistance, whereas the base material demonstrates the lowest fatigue crack propagation resistance. Microstructure evolution reveals that the fatigue crack propagation is characterized as transgranular fracture for the base material as well as the as-welded weldments and the weldment with PWHT. Moreover, the crack propagation path of the weldments shows a zigzag crack extension, especially for the weldment with PWHT, whereas the crack extension of the base material is relative straight. Electron backscattered diffraction reveals more amount of strain-induced martensite near the crack tip in the base material compared to in the as-welded weldment and in the weldment with PWHT, which is considered to be a crucial factor in the fatigue crack propagation behavior at cryogenic temperature.

中文翻译：

---

液氦温度下316LN TIG焊件疲劳裂纹扩展行为评价

摘要 在目前的工作中，研究了 316LN 钨极惰性气体 (TIG) 焊件和焊后热处理 (PWHT) 焊件在液氦温度下的疲劳裂纹扩展行为。结果表明，采用 PWHT 的焊件的疲劳裂纹扩展阻力最高，而母材的疲劳裂纹扩展阻力最低。显微组织演变表明，疲劳裂纹扩展的特点是母材、焊件和焊件的穿晶断裂。此外，焊件的裂纹扩展路径呈锯齿形裂纹扩展，尤其是焊件焊件，而母材的裂纹扩展是相对直线的。