Effects of aluminizing and combined strengthening on the fatigue property of K403 superalloy component under combined high and low cycle loading

Fatigue properties of K403 superalloy blades were tested using a combined high cycle fatigue (HCF) and low cycle fatigue (LCF) loading. Samples were tested in the as-cast, as-aluminized, and as-strengthened conditions. The strengthening treatment was wet sand blasting the blade root, followed by shot peening, and vibratory polishing. Metallographic and scanning electron microscope (SEM) fractographic examinations were conducted on the blades, including detailed characterization of the layered structures formed by aluminizing using energy dispersive spectroscopy (EDS). It has found that aluminizing created a surface which was brittle at the test temperature. Fatigue cracks initiated in the aluminized coating and propagated into the substrate, which reduced the fatigue life of the blades. However, the strengthening treatment improved the fatigue life by creating a compressive residual stress and removing a portion of the brittle outer layer of the aluminized coating.