Advanced burner-rig test for oxidation-corrosion resistance evaluation of MCrAlY/superalloys systems

Overview & Synopsis

Protective coatings are used on gas turbine components to enable them to survive in engine-operating conditions. This study presents a recently developed cyclic burner-rig test that is used to simulate helicopter engine conditions and to assess the oxidation and hot corrosion behaviour of MCrAlY coatings on nickel-base superalloys. A diluted sea-salt solution is atomised into the burner-rig to simulate hot-corrosion. Each cycle lasts 1 h with temperatures varying in the range of 900 °C to 1000 °C followed by 15 min cooling to room temperature. Specimens are tested up to 1000 such cycles. Three different NiCoCrAlYTa coating thicknesses are used to determine the influence of the Al reservoir on the lifetime of the coated MC2 superalloy. The evolving microstructural features are identified using high resolution scanning electron microscopy and energy dispersive spectroscopy and compared with isothermal testing in pure oxidising conditions. The NiCoCrAlYTa microstructure obtained after the burner-rig test has typical features of a Type 1 hot corrosion degradation, with internal oxidation and nitruration and a front of chromium and yttrium-rich sulphides. This type of advanced burner-rig test cycle is successful in reproducing the accelerated combined hot-corrosion/oxidation damage.