Creep Performance Study of Inconel 740H Weldment Based on Microstructural Deformation Mechanisms

The creep behavior of Inconel 740H weldment at the temperature of 760 °C is investigated experimentally and analytically using the deformation-mechanism-based true stress (DMTS) model. The Inconel 740H weldment specimens are prepared with the gas tungsten arc welding technique. Creep testing is performed on the Inconel 740H weldment specimens under a range of stress levels from 190 MPa to 447 MPa at the temperature of 760 °C. The DMTS model is employed to analyze the creep curves and creep rates. The model parameters for Inconel 740H weldment are determined from the analyses of the creep testing data in combination with that from the previous studies of similar materials based on the same creep mechanisms that involve grain boundary sliding and intragranular dislocation climb-plus-glide with dislocation multiplication. The creep life predictions of the DMTS model for Inconel 740H weldment agree very well with creep rupture test data within a temperature range of 700–800 °C. The fractured surfaces and longitudinal sections of creep-tested Inconel 740H weldment specimens are examined using scanning electron microscopy, which corroborates the DMTS model inference that the creep failure of Inconel 740H weldment is in a mode of predominantly intergranular fracture. The present study suggests that grain boundary sliding is the most significant controlling factor for the creep failure of Inconel 740H weldment.