Oxidation behavior of Al2O3-dispersion-strengthened MCrAlY bond coat at 1100 °C

To achieve a lower oxidation rate and a longer service life, we fabricated an oxide-dispersion-strengthened MCrAlY(M= Co and/or Ni)bond coat with alumina as the dispersion phase. The oxidation behavior of free-standing CoNiCrAlY bond coats prepared by high-velocity oxygen-fuel (HVOF) spraying were studied, using alumina-dispersion-strengthened (ADS) powder and conventional powder (Non-ADS). The microstructure and composition of the materials were analyzed by SEM, TEM, FIB, XRD, EDS, etc. Thermogravimetric experiments indicated that a lower oxidation rate for the ADS bond coat compared to the conventional one that conducted in air at 1100°C. Microscopic analysis shows that the alumina scale formed on the surface of the ADS bond coat is uniform, and there is no large obvious segregation phase formed in the alumina scale. Alumina scale is composed of equiaxed crystals on the outside and columnar crystals on the inside. For the non-ADS bond coat, the alumina scale presents a typical internally grown columnar crystal structure, but large segregation phases enriched with reactive elements in the alumina scale. The result analysis shows that the ADS bond coat with 2 wt. % alumina has the lowest oxidation rate, which is 30% lower than that of non-ADS. Due to the presence of the dispersed phases, the rapid diffusion of the reactive element Y is inhibited. This work discusses the influence of different contents of dispersed phases on the oxidation resistance of bond coat, and obtaining an outstanding service life.