DZ40M合金的热疲劳性能

Thermal Fatigue Properties of DZ40M Alloy

摘要:

采用扫描电子显微镜研究DZ40M定向凝固钴基高温合金的热疲劳性能。结果表明，随着上限温度的升高，裂纹扩展速率增加，热疲劳抗力降低。在上限温度相同时，随着保温时间的延长，热疲劳性能提高，在合金表面形成均匀致密的氧化物保护膜有利于热疲劳性能的提高。由于碳化物与基体的热膨胀系数不同，合金在受温度交替变化时，易在基体和碳化物界面处产生裂纹孔洞，从而萌生裂纹。热疲劳裂纹通过裂纹孔洞的相互连接向前扩展

Abstract:

Thermal fatigue properties of DZ40M directionally solidified cobalt-base superalloy was investigated by scanning electric microscope. The results show that the crack propagation rate increases and the thermal fatigue resistance decreases with the rise of the upper temperature. Resistance of thermal fatigue is improved with the holding time prolonging at the same upper temperature, which is caused by the formation of uniform and compact film of oxide on the surface. Due to different thermal expanding coefficients of the matrix and the carbides, crack holes are easily formed in the boundary of the matrix and carbides at alternating temperatures during thermal fatigue; as a result, cracks of thermal fatigue initiate. The interconnection of crack holes makes thermal fatigue crack propagate.