材料期刊网

The effect of an NiAl microcrystalline coating prepared by magnetron sputtering on the high-temperature oxidation behavior of NiAl-28Cr-5Mo-1Hf was investigated in static air at 1000-1150degreesC. The additions of Cr, Mo, and Hf changed the single beta-phase structure into a multiphase structure [beta-NiAl, alpha-Cr(Mo), and Heusler phase]. The NiAl-28Cr-5Mo-1Hf alloy formed a nonprotective mixed scale of Al2O3 + Cr2O3 + HfO2 and exhibited relatively large weight gains. The large weight gains were attributed to extensive internal oxidation. The sputtered NiAl microcrystalline coating remarkably improved the oxidation resistance of NiAl-28Cr-5Mo-1Hf due to the formation of a compact and adherent Al2O3 scale at all test temperatures. It was found that the theta- alpha-Al2O3 transformation caused the anomalous behavior of the oxidation-kinetics cures of the NiAl microcrystalline coating in the temperature range 1000-1150degreesC. A change in the morphology of scales occurred with the transformation.