Behavior of a Next-Generation Nickel Super Alloy Turbine Component under Direct Exposure to Gas Heat from Combustion in a Long-term Operation

In this research, the microstructural evolution and creep behavior of a second-stage vane from a gas turbine after ۱۲۰۰ long-term cycles were evaluated through microstructural examinations and creep tests. Microscopic analyses revealed an increase in the volume fraction and size of secondary phases such as gamma prime and carbides. These microstructural changes led to the embrittlement of the investigated nickel superalloy. Hardness testing results indicated an increase in hardness from ۴۲۰ Vickers to ۴۸۰ Vickers for the service-exposed vane after direct exposure to gas heat. Thermal analysis showed a ۶۰°C decrease in the complete dissolution temperature, suggesting a need for repair or rejuvenation of the alloy. The growth of gamma prime precipitates through the shearing of dislocations and the coarsening of carbides due to the inhibition of grain boundary sliding resulted in an ۱۱-hour reduction in creep life. The reference sample failed at a stress of ۲۴۷ MPa and a temperature of ۹۰۰°C after ۴۰ hours with a strain of ۹%. In contrast, the service-exposed vane exhibited a reduction in creep life and creep strain to ۲۹ hours and ۴%, respectively.

کلیدواژه ها:

Nickel Superalloy ، Carbides and γ′ - phase metallographic evaluation ، MAUD ، XRD ، Creep resistance