On the influence of the dendritic structure on the creep behavior of a Re-containing superalloy at high temperature/low stress

Despite the standard heat treatments, chemical segregations remain in MCNG, a fourth generation nickel base single crystal superalloy. Very different behaviors are observed within the dendrites and the interdendritic regions. Firstly, these areas exhibit different room temperature hardness whether in the as-received state or after being crept. Secondly, during isothermal creep at high temperature/low stress, rafting is delayed in the interdendritic regions but further evolution of the γ′ precipitates, such as topological inversion, is faster in these areas. The role of as-received microstructure on the local differences observed within the dendritic structure is discussed. Based on previous work on a first generation nickel base single crystal superalloy, an isothermal creep model, taking into account the average homogenized microstructure evolution, is proposed.