Residual stresses study in butt welded joint of Inconel 617 alloy and effect of post weld heat treatment on residual stresses

Abstract

Distribution of weld-induced residual stress plays a significant effect on the service life of a welded component. The accumulation of high residual stress accelerates the crack propagation even if the crack is of microscopic level, reducing the service life of the welded component. Prior understanding of residual stress distribution can aid in the design of a component with an adequate factor of safety and reduce the probability of failure. In the present study, two separate circumferential butt welded pipes were fabricated using Alloy 617 and then subjected to post weld heat treatment) at 720°C and 980°C. The deep hole drilling method was used to measure the distribution of residual stress. The fabrication of the welded joint was done using the hot-wire TIG welding process. High welding speeds are possible with hot-wire tungsten inert gas (TIG) welding because it uses less heat than conventional TIG welding. Using hot-wire TIG welding, the welded joint's mechanical properties, such as hardness, are improved in addition to its metallurgical properties. The computational approach is provided to analyze temperature and residual stress fields in multi-pass TIG welds with different passes. Based on ABAQUS FEA software, a coupled thermomechanical computational approach was developed to analyze the residual stress distribution on the welded joint. A 3D finite element model for Alloy 617 tube was created to estimate the welding stress field in two separate multi-pass welded joints. Mixed hardening model (kinematic and isotropic) was used during the numerical analysis. The effectiveness of the computational approach was verified with experimental measurements. The magnitude of hoop and axial residual stresses were observed to be maximum at a depth of 6 mm from the upper surface. The stress gradient in the welded zone and heat-affected zone is dramatically reduced by 70–80% of the as-welded condition during the post weld heat treatment at 980°C.