Abstract
For long life-time durability of advanced gas turbines, protective coatings, which shield the underlying substrate superalloys from oxidation and corrosion attacks, are essential requirements for the hot section components. Conventionally, MCrAlY (where M indicates Co, Ni or their combinations) is deposited on the substrate as the protective coating, as well as the bond coat of thermal barrier coating system, by using low pressure plasma spray (LPPS) and high velocity oxygen fuel (HVOF) processes. Recently, Cold spray (CS) technique has been investigated as the coating process for those coating. These coatings induce additional thermal stress due to the mismatch of thermal expansion coefficient between the substrate and the coating, which impel the substrate to be exposed to more severe conditions. Thus, thermo-mechanical fatigue strength is one of critical issue to determine the life. In this work, the damage behaviors by thermo-mechanical fatigue loading were investigated in a CS protective coated Ni-base superalloy IN738LC. The high temperature fatigue strength of protective coatings was affected by the coating process due to the residual stress induced by coating process.
