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利用开有V形缺口的平板试样,研究了GH230合金在试验最高温度分别为700、800、900和1000℃,最低温度为20℃的热循环下的热疲劳行为。研究表明,随着热疲劳试验最高温度的增加,GH230合金热疲劳裂纹扩展速率增加,但合金在不同循环温度条件下裂纹扩展长度与循环周次基本满足线性关系。通过光学显微镜和扫描电镜观察了试样的热疲劳裂纹形貌,研究了合金热疲劳损伤机制。结果表明,热疲劳主裂纹主要从V形缺口处萌生,而且主裂纹萌生和扩展方式都为穿晶断裂,同时二次裂纹也是以穿晶断裂方式扩展。当最高循环温度为9001、000℃时,合金的高温氧化进一步加速其失效。
The thermal fatigue behavior of GH230 alloy under the thermal cycling of 700, 800, 900 and 1000 ℃ with the lowest temperature of 20 ℃ was studied by using the V-notch plate samples. The results show that the thermal fatigue crack growth rate of GH230 alloy increases with the increase of the maximum temperature of the thermal fatigue test, but the linear relationship between the crack propagation length and the cycle number of the alloy basically meets the requirements at different cycling temperatures. The thermal fatigue crack morphology of the sample was observed by optical microscope and scanning electron microscope, and the thermal fatigue damage mechanism of the alloy was studied. The results show that the main thermal fatigue crack initiation occurs mainly from the V-shaped notch, and the main crack initiation and propagation modes are transgranular fracture, meanwhile the secondary crack is also propagated by transgranular fracture. When the maximum cycle temperature is 9001,000 ℃, the high temperature oxidation of the alloy accelerates its failure further.