Dissolution of fine γ' precipitates of MC2 Ni-based single-crystal superalloy in creep-fatigue regime

The dissolution kinetics of an ultra-fine γ’ precipitation occurring in the γ matrix between the standard secondary precipitates of MC2 Ni-based single crystal superalloy was investigated. Creep-fatigue experiments at 1050°C including an overheating at 1200°C were performed on oriented specimens to study the effects of fine γ’ particles on the plastic deformation. During these experiments, a decrease of the plastic deformation rate was observed just after the temperature peak. This hardening effect disappears once the fine γ’ precipitates had been dissolved. A mean time for this hyperfine precipitation dissolution could then be highlighted. Based on both simple binary diffusion and complex diffusion analysis, the mean time for the dissolution of the fine γ’ precipitates is analyzed and compared to the experimental ones. It is shown that considering only a simple binary diffusion is not sufficient and it should be considered a more complex diffusive analysis involving additional interplays.