Modification of Larson–Miller Parameter Technique for Predicting Creep Life of Materials

Abstract

Larson–Miller parameter is the most extensively used extrapolation technique for predicting creep life of metallic materials. In this technique, the Larson–Miller parameter (P) is empirically expressed as: P = T [C + log(t)] where the C is considered as a constant. This is under the assumption that iso-stress lines in the plot of log(t) versus 1/T when extended, intersects the vertical axis at 1/T = 0, which corresponds to the Larson–Miller constant C. Analysis of the literature data reveals that the intersection of the iso-stress lines at a common point is rarely met in practice. The present paper is aimed at investigating the value of Larson–Miller constant C in the Larson–Miller parameter technique. Accelerated creep tests on micro-alloyed HP40Nb steel were conducted at constant stresses in the range 47–120 MPa and temperatures 650–1050 °C for the prediction of creep life by Larson–Miller parameter. The results reveal that the Larson–Miller constant C in the expression for P is not a constant, rather, it is a linear function of applied stress. The authors proposed to modify the expression for the Larson–Miller parameter for predicting the creep life of materials.