Effect of grit blasting and subsequent heat treatment on stress rupture property of a Ni-based single-crystal superalloy SGX3

In the present study, the effect of grit blasting and subsequent heat treatment on the stress rupture properties of a third-generation nickel-based single-crystal superalloy SGX3 sheet was studied. It was found that the stress rupture life of alloy SGX3 sheet at 980 °C/250 MPa was reduced by about 60% by only vacuum heat treatment at 1100 °C for 200 h and further reduced by 20% and 70% respectively with grit blasting of 0.3 MPa/1 min and 0.5 MPa/2 min before heat treatment. The microstructure analysis results indicated that the degradation of stress rupture life of alloy SGX3 sheet by vacuum heat treatment was mainly attributed to the variation of γ/γ′ microstructure, i.e., the decrease in γ′ volume fraction and the coarsening of γ′ precipitates. Furthermore, such degradation by grit blasting and subsequent vacuum heat treatment should be attributed to the formation of cellular recrystallization with different thicknesses at the surface of alloy SGX3 sheet, which not only acts as the vulnerable site for cracks to initiate and propagate but also reduces the effective loading area.