Determination of solution temperature in an ex-service Ni-based turbine blade

Subject Areas : Materials synthesis and charachterization

Mohammad Shademani ¹ , Mohamadreza Rahimipour ² , Ali Sedaghat ³ , Mohammad Farvizi ⁴

1 - Materials and Energy Research Center
2 - Materials and Energy Research Center
3 - Materials & Energy Research Center
4 - Materials and Energy Research Center

Received: 2016-12-27 Accepted : 2017-08-29 Published : 2017-12-15

Keywords: Microstructure, Nickel- based superalloy, Rejuvenation heat treatment, Gamma prime precipitates,

Abstract :

It is well-known that the harsh operational conditions of turbine blades lead to a gradual change in the microstructure of underlying Ni-based superalloy of blades. According to this, a rejuvenation process should be conducted on turbine blades superalloys to recover their microstructures. The first and main step of rejuvenation process is the determination of appropriate solution condition in which ϒʹ precipitates dissolve in the ϒ matrix. In this study, different heat treatment conditions were applied on a Ni-based single crystal superalloy to determine its solution condition. The results of scanning electron microscopy (SEM) studies showed that with increasing the solution treatment temperature from 1275°C (3h) to 1330°C (3h), first, ϒʹ precipitates at dendritic regions dissolve and only after increasing the solution temperature to 1350°C (3h), complete solution of ϒʹ phase occurs. The full solution condition (1350°C-3h) will be used as the first step of the rejuvenation process of these blades in future studies.