superalloycoated

Superalloycoated is a term used in materials engineering to describe a protective coating applied to a nickel- or cobalt-based superalloy substrate to enhance performance at elevated temperatures. The coating can be metal, ceramic, or composite, and is chosen to improve oxidation resistance, hot corrosion resistance, wear resistance, or thermal management without compromising mechanical properties at service temperatures.

Common coating types include diffusion aluminide coatings, such as platinum- or palladium-based aluminides, which form protective aluminum oxide scales during high-temperature exposure; MCrAlY bond coats that also serve as diffusion sources for protective oxide scales; and ceramic thermal barrier coatings (TBCs), typically yttria-stabilized zirconia, applied over a metallic bond coat to reduce surface temperature. Environmental barrier coatings are used on some alloys and ceramic matrix composites to resist moisture and corrosive species.

Manufacture methods include diffusion coating processes like pack cementation and vapor-phase deposition, and protective coating applications such as plasma spray and electron beam physical vapor deposition (EB-PVD) for TBCs, with high-velocity oxy-fuel (HVOF) as an alternative.

Applications are dominated by gas turbine engines for aircraft and power generation, where coated superalloys extend service life and permit higher operating temperatures. Limitations include coating spallation, mismatch in thermal expansion between coating and substrate, added manufacturing costs, and the need for specialized inspection and maintenance.

Historically, protective coatings for superalloys evolved to address oxidation and hot corrosion in turbine environments, with diffusion aluminide and MCrAlY coatings appearing in the mid-20th century and TBCs becoming widespread in the late 20th century.