Catastrophic and early failure of third stage blades of a gas turbine was investigated. Some areas on the fracture surface of 4 blades were covered with thick black oxide layer. Quantitative microscopic measurements of primary γ′ and MC carbide phases showed that the blades were not exposed to excessive temperature. Scanning electron microscopy and energy dispersive spectroscopy analysis of oxide layer on fracture surface and stress ruptured specimens within 760–980 °C up to 100 h, and heat-treated specimens were used to calculate the blades temperature. The results revealed that oxide bifilms discontinuities and internal cracks accompanied with shrinkage cavities, nucleation and dendritic growth of γ′ precipitates, and non-uniform microstructure led to locally weakened structures at the bottom of airfoils. Accordingly, uncontrolled parameters in casting were the main reasons for commencing the failure.

研究了燃气轮机第三级叶片的灾难性和早期故障。4个刀片断裂面上的某些区域覆盖有厚的黑色氧化层。γ'和MC碳化物初生相的定量显微测量表明，叶片未暴露于高温下。扫描电子显微镜和能量色散光谱分析仪分析了在760–980°C范围内长达100小时的断裂表面上的氧化层和应力破裂的样品，并使用经过热处理的样品来计算叶片温度。结果表明，氧化物双膜的不连续性和内部裂纹伴随着收缩腔，γ'析出的形核和树枝状生长，并且微观结构不均匀导致翼型底部的局部结构减弱。因此，