The mechanism of thermal corrosion fatigue (TCF) on nickel-based single crystal superalloy and the corresponding structure shape effect

摘要

The thermal fatigue behavior under hot corrosion is studied at 25 degrees C 900 degrees C. The whole process of thermal corrosion fatigue (TCF), including crack initiation and propagation, is analyzed in detail from the perspective of driving force and the intensity factor for cracking. By controlling the Cr content in nickel-based single crystal superalloy, different hot corrosion degrees and reaction products are obtained, and its influence on the thermal fatigue mechanism of the alloy is analyzed comprehensively. It can be concluded from the research that hot corrosion has a great influence on thermal fatigue. Firstly, severe hot corrosion which induces spallation can lead to crack initiation dominantly. Secondly, the thermal mismatch between the hot corrosion products and the matrix provides a high driving force for thermal fatigue. Subsequently, the driving force can influence the thermal corrosion fatigue (TCF) process by stress concentration generated by crack tip and products shape. Finally, the loose and fragile nature of the hot corrosion products can provide a channel for crack propagation. These characteristics of thermal corrosion fatigue (TCF) behaviors are obvious in low Cr content Nickel-based single crystal superalloy.