Research on Oxidation Behavior of Novel Co-Al-W Alloy at High Temperature

The high-temperature oxidation resistance of Co-Al-W alloy, strengthened by a ternary compound gamma'-Co-3(Al, W) phase, was investigated. The kinetic data of mass gain and the cyclic oxidation behavior of the Co-Al-W alloys, including Co-9Al-7.5W (7.5W), Co-9Al-9.8W (9.8W) and Co-9.2Al-10.7W (10.7W), were studied at 800 and 900 degrees C by XRD, SEM and EPMA technologies, and they were compared with a nickel-base Manaurite900 (MAN900) alloy. The results show that the anti-oxidative ability of 9.8W alloy is the best at 800 degrees C among these alloys. But at 900 degrees C the square of mass gain of 7.5W and 9.8W alloys are much greater, while the anti-oxidant property of MAN900 and 10.7W alloys are superior to other alloys. The oxide scales at 800 and 900 degrees C exhibit a multi-layered structure, including an outer layer of Co3O4, an intermediate layer composed of complex oxides of Co, Al and W elements layer, and an internal attacked layer with oxides of Co and Al.