The thermal fatigue behavior of K125 L superalloy at the peak temperature of 1,050 °C was investigated by optical microscope(OM), X-ray diffraction(XRD), and scanning electron microscope(SEM). The experimental results show that the crack initiation sites of tested alloys are at the V-notch tip and the V-notch tip propagates by way of continuous cracking along grain boundaries. The formation of high-temperature oxides and MC carbides accelerates the crack propagation, and no secondary carbides precipitate out. Oxides between cracks are mainly the Al2O3 as well as Cr_2O_3, and carbides are Ta-rich and Tirich MC carbides.
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