Abstract: By designing the specimens with/without CoNiCrAl coatings as stepped ones to exclude other environmental factors, the effect of stress on the creep microstructure and elemental diffusion of DZ411 superalloy at 950 ℃ was studied, and the protective effect of the coating on the specimen was analyzed. The results show that the coating can significantly increase the creep life of the specimen. It is find that the greater the stress in the specimen, the higher the degree of degradation of the γ' phase and the higher the degree of compactness, especially the γ' phase in the high-stress zone is completely rafted, and that in the rest zones shows different degrees of spheroidization. The coating of the coated specimen in the high-stress zone is seriously damaged, while the coating in the low-stress and the non-stress zones only undergo slight oxidation. The degree of oxidation on the surface of the uncoated specimen increases with the increase of stress, though that in the high stress zone is more serious and with defects such as cracks and looseness, while the surface of the low stress position is still kept more complete. In addition, the element diffusion also changes with the stress, and different oxides are formed on the surface of the specimens, among which the Ti element content of the coated specimen gradually decreases from the matrix to the oxide layer surface, and decreases with the decrease of stress, while the Cr element content continues to increase from the surface to the inside and then decreases.

Key words: DZ411 superalloy, CoNiCrAl coating, stress, creep, diffusion, rafting