Failure analysis of a service-degraded gas turbine combustor liner: A metallurgical evaluation

A comprehensive destructive analysis was conducted on a rejected inner liner segment from a V2500-5 aero-engine, a critical component made from B1900 nickel-based superalloy. The investigation combined field emission scanning electron microscopy–energy-dispersive X-ray spectroscopy characterization with JMatPro thermodynamic simulations to elucidate the degradation mechanisms that led to component rejection due to severe burning and thermal fatigue cracking. The results revealed that failure was a consequence of both intrinsic material properties and service-induced degradation. Microstructurally, the superalloy exhibited severe, non-directional coarsening of γ’ precipitates, signifying a loss of the material's primary strengthening mechanism. Furthermore, a direct correlation was established between JMatPro's prediction of elemental segregation of heavy elements such as Ta and Hf and the observed microstructural flaws, including continuous carbide films and expanded eutectic islands. These flaws created inherent weaknesses prone to incipient melting and embrittlement during service. The analysis also confirmed a dual-layer thermal barrier coating (NiCoCrAlY and yttria-stabilized zirconia) and an aluminide coating, both of which showed signs of failure, further accelerating substrate degradation and ultimately leading to catastrophic component rejection.