Research On High Temperature Crack Growth Behavior And Modelling Of A Nickel-based Superalloy For Turbine Disk

Not only the traditional fatigue life design, but also the damage tolerance design was required forthe disk which is a life critical fracture part of the aero engine. However, the turbine disk is workingunder high temperature, many factors can influence the fatigue crack growth behavior, and also thecrack growth model is more complex. Accurate high temperature crack growth model is one of thekey issues which need to be solved in turbine disk damage tolerance design. Nickel-based superalloyGH742high-temperature crack growth behavior and model research were carried out, a suitable hightemperature crack growth model for the material was established and verified, and the crack growthlife prediction method was preliminarily studied. Main work and conclusions are as follows:(1) The research status of nickel-based superalloy high temperature crack growth behavior andmodel at home and abroad were summarized.(2) GH742fatigue, creep, creep fatigue and simple spectrum loading crack growth experimentswere carried out in650℃. Fracture surface morphology was observed. The results show that crackwas predominantly transgranular fracture under high temperature fatigue load with little scopeintergranular fracture. Under sustained load, the thicker the sample, the greater the crack growth rateand the crack are all intergranular. Under creep fatigue load, the crack growth rate increased whenincreasing the hold time, and intergranular and transgranular fracture are both existed.(3) Based on the superposition principle, GH742high temperature creep fatigue crack growthmodel was established. In this process, the superposition of fatigue and creep crack growth model wasnot a very good description of the material creep fatigue crack growth test results, which was betterdescribed by Saxena superposition model.(4) The influence on the life prediction caused by different integral methods in crack growthprocess was discussed, and result shows that when calculating the increment of cycle crack growth,the influence of crack length on the stress intensity factor can be ignored.(5) The model based on the superposition principle can well predict GH742crack growth rateunder high temperature spectrum load. The high temperature crack growth life prediction of GH742standard CT specimen under spectrum load is in the scope of the test result of2times.