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本文用应变控制的低周疲劳试验方法,研究了室温、350、450和550℃下,燃气轮机叶轮用钢GH34的低周疲劳性能。试验表明,各温度下的循环应力——应变特性均为循环软化。试验温度提高,低周疲劳性能下降。由于蓝脆性的发展,450℃的低周疲劳性能迅速下降,接近550℃的低周疲劳性能。COFFIN—MANSON方程中的指数α随试验温度提高而增大。高温低周疲劳裂纹的扩展,主要为Ⅱ阶段扩展,在所采用的试验条件下,没有发现蠕变引起的治晶疲劳断裂。
In this paper, low-cycle fatigue test method of strain control was used to study the low cycle fatigue behavior of gas turbine impeller GH34 at room temperature, 350, 450 and 550 ℃. Experiments show that the cyclic stress-strain characteristics at all temperatures are cyclic softening. Test temperature increased, low cycle fatigue performance decreased. Due to the development of blue brittleness, the low cycle fatigue performance at 450 ℃ decreased rapidly, which is close to the low cycle fatigue performance at 550 ℃. The exponential α in the COFFIN-MANSON equation increases with increasing test temperature. The expansion of high temperature and low cycle fatigue cracks is mainly Ⅱ phase expansion, in the test conditions used, found no creep caused by crystal fatigue fracture.