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

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小于30、30~49、50~60、61~73和74~105μm等不同粒度。发现粒径为61~73μm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30~49μm的粉末球形度最高,比表面积最大;但粒径小于30μm的粉末氧含量最高。粉末在950℃高温氧化的过程可分为2个阶段:氧化初期(0~12 h),粉末表面形成致密的NiO、Cr_(2)O_(3)和TiO_(2)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。高温暴露100 h后,粉末已氧化为NiO,表面无明显层状氧化物。

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 powder was sieved with sizes of<30,30-49,50-60,61-73 and 74-105 μ m.The results show that the powder with size of 61-73 μm has the lowest average sphericity,minimum specific surface area and lowest oxygen content.The powder with size of 30-49 μm has the highest average sphericity and specific surface area.However,the powder with size less than 30 μm has the highest oxygen content.The high-temperature oxidation process of powder 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,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.