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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。
Scanning electron microscopy study of DZ40M directional solidification of cobalt-based superalloy thermal fatigue properties. The results show that with the increase of the maximum temperature, the crack propagation rate increases and the thermal fatigue resistance decreases. When the upper temperature is the same, the thermal fatigue property is improved with the increase of the holding time, and the formation of a uniform and dense oxide protective film on the alloy surface is favorable to the improvement of the thermal fatigue property. Due to the different coefficients of thermal expansion between carbide and matrix, the alloy easily cracks at the interface between the matrix and the carbide when the temperature changes alternately. Thermal fatigue cracks propagate forward through the interconnection of cracked holes.