Transactions of Nanjing University of Aeronautics & Astronautics
Study on Ultrahigh Cycle Fatigue Performance of GH4169 Nickel-Based Alloy at 650 ℃
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Abstract:
The fatigue test between 105—109 cycles of GH4169 nickel-based superalloy commonly used in aircraft engines is carried out by ultrasonic fatigue machine at 650 ℃. The S-N curve is obtained and the fatigue fracture morphology is observed. The fatigue S-N curve presents a“step-like”shape， with the first inflection point near 1×107 cycles and the second inflection point near 1×108 cycles. There is no engineering fatigue limit， and it still shows a downward trend after 107 or even 109 cycles. The crack initiation location is related to its life. Cracks are generated on the surface below 107 cycles， while it is inside above 107 cycles. The crack initiation source in the ultra-high cycle fatigue at 650 ℃ is mainly the local intergranular fracture and casting defect of the matrix. In the phase of crack propagation， the mixed propagation of intergranular and cleavage is the main form.
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TG146
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