A new method of metal temperature estimation for service-run blades and vanes

Abstract

A NiCoCrAlYRe overlay coating, SICOAT 2453* exhibited a series of solid state transformations involving five equilibrium phase fields between room temperature and 1200°C. The largest changes in γ, γ′ and β phase fraction (over 50 v/o for γ and γ′) occurred in the temperature range 815°C to 970°C. These changes are potentially useful for metallurgical service temperature estimation, as they occur within the operating range of many combustion turbine blades and vanes. A phase fraction vs. temperature diagram was developed for SICOAT 2453 and used to estimate the local metal operating temperatures of a service-run, single crystal PWA 1483 alloy first stage blade and a polycrystalline first stage MAR M 509 turbine vane coated with the NiCoCrAlYRe alloy. The strengths and limitations of the new temperature estimation method are discussed and compared to older methods of obtaining metal temperature estimates from service-run blades and vanes.