Influence of recrystallized surface layer on high-temperature stress rupture property of DZ4 superalloy

Effect of the recrystallized surface layer on the stress rupture property and fracture behavior of DZ4 superalloy was investigated by shot peening. The results showed that the stress rupture life of DZ4 superalloy at 500 MPa and 800°C was strongly affected by the recrystallized surface layer. The recrystallized surface layer, 205 fun in depth which is approximately 8 percent of the over-all fractured surface, resulted in a 22 percent decrease in stress rupture life. And the stress rupture life sharply decreased with the increasing depth of recrystallized surface layer. Decrease of stress rupture life of directionally solidified superalloy is the results of low strength of the recrystallized surface layer, poor harmony in deformation abilities and the stress concentration caused by notch-effect between the recrystallized layer and base material.