The effect of cryogenic treatment on rejuvenation of exposed IN738LC gas turbine blade

In the present study, the service-exposed gas turbine blade was rejuvenated after 80000 hr of service. In this report, the effect of cooling on liquid nitrogen and cryogenic after two stages of solution (full and partial) was investigated. Microstructural studies by scanning electron microscopy (SEM) showed that increasing of the cooling rate in full solution resulted decrease in the size and percentage of volume fraction of γ´ precipitates after aging. whereas the cryogenic effect at full solution stage was less than the cooling rate. The effect of high cooling rate on partial solution was a decrease in γ´ precipitates volume fraction after aging compared to similar effect on full solution stage. Cryogenic treatment after partial solution increased the secondary γ´ precipitates volume fraction and size till 230 nm. High cooling rate of partial solution resulted in the maximum of hardness after aging and high cooling rate of full solution resulted in minimum of hardness after aging.