Fatigue properties of the refurbished INCO-617 alloy

The transition piece in gas turbines is an important component, which joins the combustion chamber to the turbine nozzles. The high temperature operation and thermal fatigue limits the lifetime of a component. The transition pieces are made from an alloy, which is considerably expensive. Consequently, the life extension of the alloy through a refurbishment process will be fruitful. In the present study, a heat treatment of the INCO-617 alloy previously used over 30,000 h is considered. Three heat treatment conditions are taken into account. The microstructures and elemental composition of the alloy before and after the heat treatment are investigated. It is found that the heat treatment of the alloy for 1 h improves partially the cavitations at grain boundaries. The fatigue response of the workpiece does not improve considerably; however, the tensile fractographs of the heat-treated workpiece show the dimples at grain boundary facets, which are the evidences for the ductility of the workpiece.