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焊后热处理对308L奥氏体不锈钢焊缝蠕变-疲劳损伤机制的影响

Effect of post weld heat treatment on damage mechanism of gas tungsten arc welded 308L stainless steel during creep-fatigue

  • 摘要: 对钨极氩弧焊308L奥氏体不锈钢焊接接头在高温下进行应变控制的蠕变-疲劳试验,使用光学显微镜和扫描电镜分别对焊态试样和焊后热处理试样进行观察,同时用能谱议(EDS)对析出相进行判定,分析微观结构演变和裂纹扩展机制,研究焊后热处理对焊缝金属微观组织以及焊接接头蠕变-疲劳破坏行为的影响.结果表明,经高温焊后热处理,焊缝金属中δ-铁素体的连续网状结构被打破,裂纹扩展模式由沿晶扩展向混合型扩展转变,从而提高了焊接接头的蠕变-疲劳抗力.

     

    Abstract: Strain controlled creep-fatigue tests were conducted on gas-tungsten-arc welded (GTAW) 308L stainless steel joints at elevated temperature. The influence of post-weld heat treatment (PWHT) on the ferrite morphology and creep-fatigue behaviors of the weldment were investigated. The microstructure evolution and crack propagation behavior of the as-welded and post weld heat treated (PWHT) weldments during creep-fatigue test were examined with optical microscope (OM) and scanning electron microscope (SEM). Energy dispersive spectroscopy (EDS) was also used for intermetallic phase identification. It was found that high temperature PWHT reduced the amount of δ-ferrite in the weldment, and the creep-fatigue life increased with the increasing PWHT temperature. After high temperature PWHT, the crack propagation character was transformed from intergranular mode to mixed mode. High temperature PWHT resulted in the broken of the continuous δ-ferrite network and promoted the creep-fatigue resistance of the weldment.

     

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