Strengthening Alumina Protective Layer on MCrAlY Atmospheric Plasma Sprayed Coating by Chromate Processing

The high temperature oxidation resistance behavior of atmospheric plasma sprayed CoNiCrAlY coating with a thin layer of Cr₂O₃ employing chromate treatment was investigated. The high-temperature oxidation test was performed at 1423K for 7.2, 14.4 and 32.4ks, respectively. The formation of the oxide layer on the CoNiCrAlY coatings with Cr₂O₃ thin layer by chromate treatment was compared with that of the non-Cr₂O₃ thin layer. The oxide layer formed on the both types of MCrAlY coatings grows with increasing the elevated temperature and the holding time. Also, the thickness of the oxide layers was proportional to the square root of time. The thickness of the oxide layer on CoNiCrAlY coatings with the thin layer of Cr₂O₃ was only 60% as compared with that of the non-Cr₂O₃ thin layer in high temperature oxidation tests at 1423K.