Oxygen Absorption Characteristics and High Temperature Oxidation Behavior of Nickel-Based Superalloy Powder

The sphericity, specific surface area, oxygen content, surface oxygen state and high temperature oxidation characteristics of nickel-based super alloy powders with various particle sizes were studied. The oxygen absorption characteristics of the alloy powder at room temperature and the oxidation characteristics at high temperature were obtained. The argon-atomized powder was sieved with sizes of<30, 30-49, 50-60, 61-73 and 74-105 mu m. The results show that the powder with size of 61-73 mu m has the lowest average sphericity, minimum specific surface area and lowest oxygen content. The powder with size of 30-49 mu m has the highest average sphericity and specific surface area. However, the powder with size less than 30 mu m has the highest oxygen content. The high-temperature oxidation process of powder at 950 degrees C can be defined as two stages: the initial stage of oxidation (0-12 h) and the later stage of oxidation (>12 h). At the initial stage of oxidation, a dense mixed oxide layer of NiO, Cr(2)O(3 )and TiO(2 )is formed on the powder surface. After oxidation for 12 h, the mixed oxide layer peels off and the oxidation resistance begins to decrease. After oxidation for 24 h, the mixed oxide layer peels off obviously and exposes substrate, resulting in complete failure of oxidation resistance. After oxidation for 100 h, the powder is mainly oxidized into NiO without obvious oxide layer existing on the surface.