Effect of Crystal Orientation on Cyclic Plastic Behaviors of Partially Recrystallized Single Crystal Nickel-based Superalloy

Abstract

Surface recrystallization (RX) is one of the main causes of fatigue failure of heavy gas turbine single crystal (SX) blade and thus a threat to safe long-time operation. Using crystal plasticity model, the effects of primary and secondary crystal orientation on the cyclic plastic deformation behaviors of recrystallized SX nickel-based superalloy was investigated via crystal plasticity finite element simulation. The results show that primary orientation has significant effect on the accumulated plastic shear stain γ of the recrystallized SX superalloy: the maximum accumulated plastic shear strain γmax occurs in SX matrix near RX transverse grain boundary; the maximum accumulated plastic shear strain γmax of RX-SX system increases with increasing primary orientation(β); the maximum accumulated plastic shear strain γmax at β=15° is 31.6% larger than that at β=0°; the maximum accumulated plastic shear strain γmax decreases first and then increases with the increasing of the secondary orientation(θ) from 0° to 90°, with the lowest value of γmax at θ=43°, which is 1.4% smaller than that at θ=0° and θ=90°. The study shows that the crystal orientation can be optimized to reduce the effect of recrystallized grain on the fatigue property of SX nickel-based superalloy.