Effect of Sandblasting Process on the Oxidation Behavior of HVOF MCrAlY Coatings
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Surface characteristics, such as topography and roughness (R a), are important in affecting the isothermal oxidation behavior of MCrAlY coatings. In this study, the effect of sandblasting on the oxidation behavior of HVOF thermal-sprayed MCrAlY coatings was investigated. Oxidation tests were conducted under isothermal conditions at 1050 °C for different periods. The R a of the bondcoat was approximately 12 μm. Before and after oxidation, the thermally-grown scale composition and morphology were analyzed using scanning electron microscope (SEM/EDX) and X-ray diffraction. The results showed that the oxide scale that formed on the as-sprayed coatings was a mixture of Al2O3 and spinel, while the oxide formed on the sandblasted coating was composed mainly of Al2O3. In addition, with increasing R a of the bondcoat, the oxidation rate progressively decreased and the amount of Al2O3 increased compared with the as-sprayed coating. Scanning electron microscope analysis showed that the thickness of the scale layer on the sandblasted CoNiCrAlY coating at 1050 °C was much thinner than that on the as-sprayed one.
KeywordsMCrAlY coatings Sandblasting Thermally grown oxide (TGO) Surface roughness
The authors are grateful to the Poudr afshan Company for financial support and their assistance with the HVOF spraying.
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