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In this paper, the crack initiation and propagation laws of GH4169 under thermal-shock load were investigated. It was found that the development of main cracks experienced three stages: accelerated growth in the small crack stage, decelerated growth in the long crack stage and finally discontinued growth. With the increase of temperature, the crack initiation life decreases and the propagation rate increases, the crack initiation life at 600°C is six times to that at 700°C. A thermal fatigue crack growth model was proposed to character the whole crack growth process, and a comparison was drawn with the Paris and Z-H model. The results show that the model is applicable to predict the whole process growth rate of thermal fatigue cracks.

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