Creep failure mechanism of -oriented thin-wall Ni3Al-based single crystal superalloys

Abstract

Currently, thin-wall structures are widely employed in aviation engine turbine blades to enhance cooling efficiency. However, the mechanical properties of thin-walled structures exhibit significant sensitivity to thickness. This study investigates the creep behavior of a <111>-oriented Ni3Al-based single-crystal superalloy with different thicknesses (0.3, 0.5, 0.8 mm) at 1100 °C/137 MPa. The results indicate a significant reduction in creep life with a decrease in wall thickness. The mechanism of various influencing factors on different creep stages was analyzed from both microscopic and macroscopic perspectives combined with finite element modeling. The alteration in stress state from thick-wall to thin-wall influences the number of slip systems that are activated, which mainly affects the primary and steady-state creep stages. Surface oxidation as time-dependent damage leads to non-invasive crack formation, somewhat increasing the steady-state creep strain rate of thin-wall samples. The accumulation and propagation in varying wall thicknesses of cleavage microcracks primarily influence the steady-state and tertiary creep stages, respectively, thereby exacerbating the thickness debit effect.