• Vasudev, Hitesh
• Prashar, Gaurav

Abstract

<jats:p> Surface degradation (oxidation/corrosion/erosion) at elevated temperature is encountered commonly in engineering industries like gas turbines and thermal power plants. [Formula: see text]CrAl[Formula: see text] coatings which came into the picture in 1960s were used widely for surface protection in the elevated-temperature section of the gas turbine engines and in boilers to combat oxidation/corrosion/erosion. Among them, [Formula: see text]CrAlY ([Formula: see text], Co or [Formula: see text]) were developed to be used as the overlay coatings and bond coat (BC), which offer a combination of multiple features such as oxidation, corrosion and ductility. [Formula: see text]CrAlY coatings form a second layer of aluminum oxide beneath the chromium oxide layer at elevated temperatures which minimizes the oxidation/corrosion/erosive wear rates. But the desire to increase combustion efficiencies of power plants and gas turbine engines along with lower CO<jats:sub>2</jats:sub> emissions poses a significant challenge for coating design. As the temperature surpasses 900<jats:sup>∘</jats:sup>C, NiCrAlY coating degrades quickly due to nonregeneration of chromia or alumina. The research and development (R&amp;D) efforts are focusing continuously on improving the existing [Formula: see text]CrAl[Formula: see text] coatings or developing new sustainable [Formula: see text]CrAl[Formula: see text] coatings with improved oxidation performance. In this review, the roles of the alloying elements, microstructures, post-deposition treatment techniques and different deposition processes in the elevated-temperature oxidation/corrosion performance of [Formula: see text]CrAl[Formula: see text]-based alloys have been explored in detail. </jats:p>

Topics

• Deposition
• impedance spectroscopy
• microstructure
• surface
• corrosion
• chromium
• aluminum oxide
• aluminium
• combustion
• ductility