Abstract
AbstractThe oxidation and corrosion resistance of superalloys in present use is often enhanced by the application of MCrAlY overlay coatings, where M is a combination of cobalt and nickel. The properties of the basic coating may be further improved by suitable elemental additions. In this work, standard CoNiCrAlY coatings were augmented by the addition of 4·5 or 3 wt-%Ta. The coatings were deposited onto two different substrates, IN 100 and MAR M002, then oxidised at 1000 and 1050°C for up to 500 h. It was found that the addition of tantalum to the coating had a significant effect upon oxidation resistance only if the superalloy substrate was present. The tantalum within the coating was found to react, with titanium and carbon moving into the coating from the substrate with the formation of (Ta,Ti) carbides of the MC type. This reduced the amount of titanium in solid solution within the alumina scale and thus improved the oxidation resistance. The morphologies of particles within the coatings and oxide sc...
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