High-temperature hot-corrosion effects on the creep–fatigue behavior of a directionally solidified nickel-based superalloy: Mechanism and lifetime prediction

Creep–fatigue experiments were performed at 850℃ on bare and salt-coated directionally solidified Ni-based superalloy DZ125. Experimental test results showed that the salt-coated sample exhibited lower lifetime than that of the bare sample under all stress conditions. This reduction is found to correlate directly with the higher probability of crack initiation, due to surface micro-structural degradation and higher actual stress as a result of the decrease in effective bearing area. A modified damage accumulation model considering the creep, fatigue, and hot-corrosion interaction effect was proposed to predict the corrosion–creep–fatigue lifetime. In this model, a critical high-temperature hot-corrosion exposure time was proposed and was introduced using the Miller linear damage accumulation model. The predicted lifetimes correspond remarkably well with the experimental results.