Abstract
The low-pressure plasma spray coating process has been established in the field of gas turbines and is used for parts (turbine blades, duct segments, etc.) which are exposed to corrosive gases at high temperatures. Overlay coatings based on the MCrAlY alloy system (M is Ni, Co or Fe) are commonly employed as oxidation- and corrosion- resistant coatings. Mechanical properties, such as low-cycle fatigue lives, of CoCrAlY, NiCrAlY and CoNiCrAlY coated systems were investigated at high-temperature as compared with the uncoated conventional IN738LC, unidirectional solidified CM247LC and single crystal CMSX-2.Low-cycle fatigue properties of the MCrAlY coated superalloys at high-temperature (IN738LC : 1123 K, CM247LC, UMSX-2: 1173 K) showed only a little superior performance in comparison with the uncoated results. It was because that the low-cycle fatigue cracks initiated at casting cavities inside the substrate in any cases and the low-cycle fatigue crack initiation due to coatings could not be observed. It seems to be possible to evaluate the low-cycle fatigue lives of the MCrAlY coated superalloys at high-temperature by using the uncoated results.
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