Thermal fatigue crack initiation in K465 superalloy

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ÎÄÕÂÒ³Â룺71 - 77

Key words£ºthermal fatigue£» oxidation£» creep£» crack initiation

Abstract: Thermal fatigue crack initiation of K465 superalloy was studied by optical microcope and scanning electron microscope(SEM). The maximum temperature and its corresponding holding time during thermal fatigue were respectively 950¤@¡æ for 100¤@s and 300¤@s, 1¤@000¤@¡æ for 100¤@s and 1¤@050¤@¡æ for 100¤@s and 300¤@s. The minimum temperature was 20¤@¡æ. The data of initiation lives shows that increasing the maximum temperature or holding time at peak temperature decreases TF crack initiation life and the effect of holding time is more distinct than that of peak temperature. The metallographic observation presents that TF crack initiates at voids aggregation damage zones(VADZs), carbide fracture damage zones(CFDZs), cracked carbide and phases interface. VADZs basically result from creep-fatigue interaction deformation whereas CFDZs is mainly induced by oxidation.