Effect of long-term service exposure on microstructure and mechanical properties of Alloy 617

The present work was carried out to investigate the effect of long-term service exposure on microstructure and mechanical properties of a gas turbine hot gas path component, made of Alloy 617. The results showed significant service-induced microstructural changes, such as excessive grain boundary Cr-rich M23C6 carbides formation and some oxidation features in the exposed material in compare with the solution-annealed material. Also it was found that the yield strength and hardness of the alloy have increased while the ductility of the alloy has decreased. In the similar test conditions, the stress-rupture life of the exposed alloy decreased considerably compared to the solution-annealed sample, which could be attributed to the microstructural degradation, especially formation of continuous M23C6 carbides on grain boundaries.

Research highlights
► The major microstructural degradation is grain boundary M23C6 carbides formation.
► The major mechanical properties degradation is decreasing in ductility of the alloy.
► Formation of continuous carbides along GBs reduced the rupture life of the alloy.