Influence of High-Temperature Aging Time on Microstructure and Stress Rupture Property of Directionally Solidified DZ951 Ni-Based Superalloys

Abstract:

Influence of high-temperature aging time on microstructure and stress rupture property of DZ951 superalloys was investigated by optical microscopy (OM) and scanning electronic microscopy (SEM). The results reveal that carbide changes from skeleton-like of as-cast alloy to block-like and discontinuously distributes in grain boundary when the alloy is aged at 1130 °C. g￠ cubicity decreases and the size of g￠ phase increases with the elongation of holding time at 1130 °C. g￠ coarsens and rafts when the holding time is 6 h. For solid solution of some g￠, fine and spherical g￠ phase precipitates during the following cooling process after 1130 °C aging treatment. The volume fraction of fine g￠ phase increases with prolonging the holding time. The stress rupture life of DZ951 alloy at 1100 °C/60 MPa reduces and the elongation increases with the prolongation of holding time. Coarsening and rafting of g￠ is deleterious to the stress rupture life for alloys.

Key words:superalloy; high-temperature aging; microstructure; stress rupture property