Correlation of the microstructural degradation and mechanical strength of Ni-based superalloy after thermal exposure

Abstract

Many hot gas components in gas turbine are made of Ni-based superalloy because of their high temperature performance. During the operation of power generation gas turbines, the blades and other elements of hot gas path suffer service induced degradation which may be natural or accelerated due to different causes. The degradation or damage may have a metallurgical or mechanical origin and results in reduction of reliability and availability. It also increases risk of failure occurring. Also, due to blade material metallurgical deterioration, the material creep, fatigue, impact and corrosion properties decrease. There are different factors which influence blade lifetime as design and operation conditions but the latter are more critical. In order to have an instrument for the deterioration evaluation of gas turbine blade alloy, it is necessary to correlate the influence of microstructural degradation to the change in mechanical properties. In this work, we survey the effect of long-term thermal exposure on microstructure and mechanical properties. The degradation of mechanical properties due to the exposure temperature and time has been examined and correlated with the microstructural changes during the long-term thermal exposure