Thickness Debit in Creep Properties of PWA 1484

Abstract

The effect of section thickness on the creep properties of a single crystal superalloy, PWA 1484 was investigated. For this purpose, a series of isothermal, constant load creep tests were conducted on uncoated sheet specimens in air at temperatures ranging from 760C to 982C and at stresses varying from 207 MPa to 758 MPa. The average time to reach 1% creep strain showed very weak dependence on specimen thickness at all test conditions. In contrast, the thickness debit associated with rupture life showed a complex dependence on test conditions. For example, creep rupture lives obtained at 760C and 758 MPa decreased sharply (60%) with a reduction in specimen thickness from 3.18 mm to 0.38 mm. However, rupture lives of specimens tested at 871C and 982C exhibited a relatively modest dependence on specimen thickness. The results have been interpreted qualitatively in terms of the effect of plastic constraint on the deformation and fracture of ligaments between the interdendritic creep voids created during creep deformation.