Comparison of inward and outward grown Pt modified aluminide diffusion coatings on a Ni based single crystal superalloy |
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Authors: | J Angenete K Stiller |
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Affiliation: | Department of Experimental Physics, Chalmers University of Technology and Göteborg University, SE-412 96 Göteborg, Sweden |
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Abstract: | Two commercial Pt modified aluminide coatings (RT22 and MDC150L) on the same single crystal Ni-based superalloy (CMSX-4) were studied by: scanning electron microscopy; transmission electron microscopy; energy dispersive X-ray spectrometry; and gravimetry. The RT22 coating is an inward grown coating (high activity), while MDC150L is produced by outward growth (low activity). Samples were oxidised in still laboratory air at 1050 °C for various times up to 2000 h. It was found that the outward grown coating produced a slower growing oxide that was more spallation resistant. Several possible reasons for this were identified including: coating purity; coating surface topography; and ductile to brittle transition temperature. The microstructural differences between the two coatings in the as-coated condition were investigated and the development of their microstructure during heat treatment was described. A model for coating growth during heat treatment was proposed. |
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Keywords: | Platinum modified aluminide diffusion coatings RT22 MDC150L CMSX-4 High temperature oxidation |
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