316L不锈钢焊接接头高温低周期疲劳显微结构变化和断裂特征

Microstructure and Fracture Behavior of 316L Stainless Steel Welded Joints under High Temperature Low Cycle

本研究对316L奥氏体不锈钢母材和焊缝分别进行高温低周疲劳试验,对试样的微观结构和裂纹扩展形貌进行观察,分析母材和焊缝在高温低周疲劳循环应力响应下的位错结构和损伤机制。结果表明,316L奥氏体不锈钢母材在试验过程中由于位错增殖和位错湮灭导致发生循环硬化和循环稳定,在焊缝中由于位错湮灭导致发生循环软化。母材和焊缝在连续低周疲劳试验中裂纹主要以穿晶方式扩展,焊接接头处孔洞的连接是最终导致焊接接头疲劳断裂的主要机制。

Low cycle fatigue tests of 316 Laustenitic stainless steel base metal and weldment were carried out at 873 Ktemperature.The microstructure and crack propagation evolution in the specimens were examined experimentally.The effect of tensile dwell on the low cycle fatigue cyclic stress response and damage mechanism of base and weld metal were investigated.The results show that clear cyclic hardening and cyclic saturation stage are observed in base metal whereas continuous cyclic softening is observed during continuous low cycle fatigue in weldment.Transgranular propagation of crack is the main character during continuous low cycle fatigue.The connection of the hole at the welded joint is the main mechanism that leads to the fatigue fracture.