镍基高温合金粉末的室温吸氧特性与高温氧化行为

Oxygen absorption characteristics and high temperature oxidation behavior of nickel-based superalloy powder

摘要:

本文研究了不同粒径镍基高温合金粉末的球形度、比表面积、氧含量、表面氧状态和高温氧化特征,总结了粉末在室温下的吸氧特性与高温氧化行为。将氩气雾化粉末筛分为<30 μm、30 ~ 49 μm、50 ~ 60 μm、61 ~ 73 μm和74 ~ 105 μm等不同粒度。发现粒径为61 ~ 73 μm的粉末平均球形度最低,比表面积最小,且氧含量最低；粒径为30 ~ 49 μm的粉末球形度最高,比表面积最大。但粒径小于30 μm的粉末氧含量最高。粉末在950 ℃高温氧化的过程可分为两个阶段。氧化初期(0~12 h),粉末表面形成致密的NiO、Cr2O3和TiO2混合氧化层。氧化后期(大于12 h),混合氧化层脱落,抗氧化性失效。氧化24 h后氧化层明显脱落并暴露基体,抗氧化性彻底失效。高温曝露100 h后,粉末已氧化为NiO,表面无明显层状氧化物。

Abstract:

The sphericity, specific surface area, oxygen content, surface oxygen state, and high temperature oxidation characteristics of nickel-based superalloy 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 powders were sieved into different sizes of <30 mm, 30~49 mm, 50~60 mm, 61~73 mm, and 74-105 mm. The results show that the powders with size of 61~73 μm have the lowest average sphericity, minimum specific surface area, and lowest oxygen content. The powders with size of 30~49 μm have the highest average sphericity and specific surface area. However, the powder less than 30 μm has the highest oxygen content. The high-temperature oxidation process of powders at 950 ℃ 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, Cr2O3 and TiO2 was formed on the powder surface. After 12 hours oxidation, the mixed oxide layer peels off and the oxidation resistance begins to fail. After 24 hours oxidation, the mixed oxide layer peels off obviously and exposes the substrate, resulting in complete failure of oxidation resistance. After 100 hours oxidation, the powder was mainly oxidized into NiO and no obvious oxide layer exists on the surface.