合金元素对Co-Al-W合金高温氧化行为的影响

Effect of alloying elements on oxidation behavior of Co-Al-W alloys at high temperature

研究新型Co-Al-W合金在800和900℃空气中氧化动力学及元素Mo、Nb、Ta和Ti对合金高温氧化行为的影响。结果表明:在800℃氧化100 h后,Co-8.8Al-9.8W(摩尔分数,%)和Co-8.8Al-9.8W-2Ta合金的质量增加较小,表明其抗高温氧化能力较强;在900℃氧化时,Co-8.8Al-9.8W-2Mo、Co-8.8Al-9.8W-2Nb、Co-8.8Al-9.8W-2Ta和Co-8.8Al-9.8W-2Ti合金的质量增加小于Co-8.8Al-9.8W合金的,表明加入合金元素可以提高合金的抗高温氧化能力;在不同温度下,Co-Al-W合金氧化膜表面出现团聚、开裂和脱落现象;氧化膜分为3层,外层为Co3O4氧化物,中间层为W、Al和合金元素的复杂氧化物,内层为Co和Al的氧化物。从合金氧化动力学曲线来看,在800℃时合金元素增强Co-Al-W合金抗高温氧化能力由强至弱依次为Ta、Ti、Mo、Nb;在900℃时按Ti、Ta、Mo、Nb顺序依次减弱。

The oxidization kinetics of novel Co-Al-W supperalloys in air at 800 and 900 ℃,and the effects of alloying elements（Mo,Nb,Ta,Ti） on oxidation behavior of Co-Al-W alloys at high-temperatures were investigated.The results show that after being oxidized at 800 ℃ for 100 h,the mass gain of Co-8.8Al-9.8W or Co-8.8Al-9.8W-2Ta is less,indicating that they have better anti-oxidative ability than other alloys at 800℃.After being oxidized at 900 ℃,the mass gain of Co-8.8Al-9.8W-2Mo,Co-8.8Al-9.8W-2Nb,Co-8.8Al-9.8W-2Ta or Co-8.8Al-9.8W-2Ti is less than that of Co-8.8Al-9.8W alloy,indicating that for anti-oxidant property,Co-8.8Al-9.8W-2Mo,Co-8.8Al-9.8W-2Nb,Co-8.8Al-9.8W-2Ta and Co-8.8Al-9.8W-2Ti alloys are superior to Co-8.8Al-9.8W alloy.There are agglomeration,voids at local scale/alloy interface,crack and deterioration in the oxidation films on Co-Al-W alloy surfaces at different temperatures.The oxide scales exhibit multi-layered structure including an outer layer of Co3O4 oxide,an intermediate mixed layer of oxides of W,Al and alloying elements and an internal attacked layer of oxides of Co and Al.According to the fitted oxidization kinetic curves,the ability of alloying elements（Mo,Nb,Ta,Ti） on the anti-oxidation of Co-Al-W alloy is in an decreasing order of Ta,Ti,Mo,Nb at 800 ℃,but Ti,Ta,Mo,Nb at 900 ℃.