High temperature oxidation behaviour of combustion flame sprayed CoNiCrAlY coatings

摘要

This paper investigates the high temperature oxidation behaviour of combustion flame sprayed CoNiCrAlY coatings. Three CoNiCrAlY coatings with different fractions of internal oxides were prepared by varying the standoff distance and the oxygen-to-acetylene ratio. The high temperature oxidation behaviour of the combustion flame sprayed CoNiCrAlY coatings were examined in air at 1100 degrees C. Microstructural analysis revealed that spinel oxides and alumina scale formed in the CoNiCrAlY coatings which have low content of internal oxide stringers. NiCo-oxides, which exhibit polyhedral morphology, were found in the coating with high content of internal oxide stringers. In addition, it is found that the internal oxidation initiated in the concave regions at the oxide/coating interface and internal nitridation occurred at long exposure conditions.