固溶处理对304H焊接接头高温蠕变疲劳性能的影响

采用具有保持时间的高温蠕变疲劳试验,研究了304H不锈钢焊接接头在相同条件下焊态和固溶态焊接接头蠕变疲劳寿命,使用断口扫描电镜、透射电镜、金相显微镜分析了断裂失效机理及裂纹扩展走向。结果表明,固溶处理可以显著提高焊接接头蠕变疲劳寿命,固溶态焊接接头蠕变疲劳寿命约为焊态的1. 6倍;焊态下断口主要呈穿晶韧窝断裂特征,固溶处理试样断口呈现穿晶与沿晶混合断裂特征,裂纹从纤维区向结晶区扩展断裂。两种状态均有脆性相碳化铬析出,但固溶处理后Cr的析出率降低,延迟了脆性相的生成;同时,固溶处理后晶粒变大,提高了蠕变强度,这些因素导致固溶态304H焊接接头蠕变疲劳寿命的增加。

Effect of Solution Treatment on the High-temperature Creep-fatigue Properties of 304H Welded Joint

The creep-fatigue life of the as-welded and solution treated 304H stainless steel welded joints under the same conditions was studied using the tests of high temperature creep fatigue with a holding time,and the fracture failure mechanism and propagation trend of the crack were analyzed using fracture scanning electron microscopy,transmission electron microscopy and metallographical microscopy.The results show that solution treatment can significantly improve the creep fatigue life of welded joint,and the creep fatigue life of the solution treated welded joint was about 1.6 times of the life of the as-welded joint;The fracture under the as-welded state mainly exhibited the characteristics of transgranular dimple fracture,and the fracture of solution treated specimen exhibited characteristics of transgranular and intergranular mixed fracture,and the crack propagates from the fiber zone to crystallization zone.There was precipitation of brittle carbon chromium compound under both states,but the rate of precipitation of Cr was reduced after solution treatment,which delays the formation of brittle phases;Meanwhile,the creep strength was improved due to increased size of grains after solution treatment.These factors led to the increase of the creep-fatigue life of 304H welded joints.