Thermal fatigue crack initiation in K465 superalloy
(1.Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China2.中围科学院金属研究所，沈阳1100163.Department of Superalloys, Institute of Metal Research, Chinese Academy of Sciences,Shenyang 110016, China)
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℃ for 100s and 300s, 1000℃ for 100s and 1050℃ for 100s and 300s. The minimum temperature was 20℃. 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.
Key words: thermal fatigue； oxidation； creep； crack initiation