Abstract
The surface of metal parts operating at high temperature in energy production and aerospace industry is typically exposed to thermal stresses and oxidation phenomena. To this aim, plasma spraying was employed to deposit NiCoCrAlYRe coatings on metal substrates. The effects of early-stage oxidation, at ~1100 °C, on their microstructure were investigated. The partial infiltration of oxygen through some open pores and microcracks embedded in coating microstructure locally assisted the formation of a stable Al2O3 scale at the splat boundary, while the diffusion of Cr and Ni and the following growth of Cr2O3, Ni(Cr,Al)2O4 and NiO were restricted to Al depleted isolated areas. At the same time, a continuous, dense and well adherent Al2O3 layer grew on the top-surface, and was somewhere supported by a thin mixed oxide scale mainly composed of Cr2O3 and spinels. Based on these results, the addition of Re to the NiCoCrAlY alloy is able to enhance the oxidation resistance.
Highlights
IntroductionThe application of ceramic thermal barrier coatings (TBCs) is well-suited for this challenge, by reducing the heat flux and the temperature at the surface of the underlying component [2]
High-temperature coatings are commonly employed to protect the surface of metal components operating in energy production and aerospace industry, with the purpose to improve their resistance to oxidation and hot-corrosion phenomena, as well as to prolong their lifetime [1].High-temperature coatings are potential tools for increasing the efficiency of thermal engines.The application of ceramic thermal barrier coatings (TBCs) is well-suited for this challenge, by reducing the heat flux and the temperature at the surface of the underlying component [2]
High-temperature aging produced some effects of oxidation and oxide scale formation
Summary
The application of ceramic thermal barrier coatings (TBCs) is well-suited for this challenge, by reducing the heat flux and the temperature at the surface of the underlying component [2]. In this context, metal coatings can be successfully adopted to cover turbine components in order to improve their environmental resistance, without compromising their structural stability and mechanical strength [3,4,5]. Plasma spraying is a cost-effective technology to manufacture MCrAlY coatings In this process, a gas plasma is employed as heat source to process the powder-based raw material. The powder particles are injected in the plasma jet by a carrier gas, and melted and accelerated toward the substrate, where they impact at high speed and quench, producing the build-up of a coating with unique microstructure
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