CREEP DATA ANALYSES OF A COLUMNAR-GRAINED NICKEL-BASE SUPERALLOY BY CONVENTIONAL AND BETA-ENVELOPE METHODS

Creep-rupture properties of a columnar-grained nickel-base superalloy have been evaluated over a wide temperature range (1033 to 1311 K) and stress levels (80 to 850 MPa). Creep data analyses based on the conve ntional approach as well as on a new graphical method-the beta-envelop e method (Ref1)-have been carried out for creep strain and life estima tion purposes, The relation between minimum creep rate of the alloy wi th the applied stress obeys simple power law, whereas the rupture data of the ahoy fits well to the Larson-Miller parameter. Also, the Monkm an-Grant relation between the minimum creep rate and the rupture life produces a trend with some degree of scatter in the data. The latter r elation in its generalized form by the beta-envelope method exhibited the best correlation,vith significantly reduced scatter in the data.