INFLUENCE OF CRYSTALLOGRAPHIC ORIENTATION ON CREEP BEHAVIOR OF ALUMINIZED NI-BASE SINGLE CRYSTAL SUPERALLOYS

摘要

The effect of chemical compositions and secondarycrystallographic orientation dependence on the formation ofdiffusion layer and creep behavior were investigated. Three alloysof different generations: PWA 1480 (1~(st) generation), CMSX-4 (2~(nd)generation) and TMS-75 (3~(rd) generation), were studied. Afteraluminized coating process, creep rupture test were performed at900 °C and 392 Mpa. The creep rupture properties of the alloyswith and without the aluminized coating treatment were compared.The coating treatment resulted in a significant decrease in rupturelives for three alloys. No reductions in rupture elongation wereobserved. Creep strength was significantly degraded withaluminide coating due to the diffusion layers formed undercoating layer. Creep fractures of the coated materials wereessentially controlled by the crack nuclei in the coated layer. Itwas also found that the specimens with (100) side-surface showedlonger creep rupture life than the specimens with (110) sidesurface,which means the results were anisotropic with respect tothe secondary orientation which is normal to the primaryorientation. The anisotropic creep behavior was caused by thedifferent arrangement of {111}<101> slip systems between thetwo side-surface specimens. The results obtained in this studysuggest the importance of secondary orientation normal to thecomponent surface on designing the single-crystalline turbineblades.