Abstract
The effect of grain boundary orientation on the creep behaviour of a directionally solidified nickel base superalloy (CM 247 LC alloy) has been studied at 1123 K in the stress range 400–500 MN m−2. The variation of minimum creep rate with orientation in the alloy can be related to anisotropic slip and early onset of tertiary creep in specimens with inclined boundaries. Transgranular fracture in longitudinal specimens occurred by crack like cavity growth along γ–γ′ rafts which developed in the initial stages of creep deformation. In specimens with inclined boundaries, intergranular fracture occurred by cracklike void growth and power law creep may have made a significant contribution to the growth of voids.
MST/2097
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