一种镍基单晶高温合金的恒温氧化行为

通过静态增重法对一种镍基单晶高温合金在900℃和1000℃的恒温氧化行为进行了测定，并利用X射线衍射和扫描电镜对氧化产物进行了分析。结果表明，该合金在900℃和1000℃均为完全抗氧化级，900℃的氧化速率明显低于1000℃的氧化速率。合金的氧化产物以(Ni,Co)O为主，并形成了较多的α-Al₂O₃ 和较少量的Cr₂O₃，同时形成了CrTaO₄及（Ni,Co）Al₂O₄和 Co(Al,Cr)₂O₄等尖晶石氧化物。氧化物呈层状分布，(Ni,Co)O在最外层，而Al₂O₃在内层。另外，在靠近α-Al₂O₃层的合金基体中出现了内氮化物。

ISOTHERMAL OXIDATION BEHAVIOR OF A SINGLE CRYSTAL NICKEL-BASED SUPERALLOY

The oxidation behavior of a single crystal superalloy at 900℃ and 1000℃ in air was investigated by using discontinuous thermogravimetric analysis (TGA). The oxidized samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed the oxidation kinetics of the alloy at 900℃ and 1000℃ followed parabolic law basically. The oxidation resistance of the alloy at 900℃ and 1000℃ was the first grade, while the rate of oxidation at 1000℃ was higher than that at 900℃. The oxidation scales were composed of (Ni,Co)O prevalently. However,α-Al₂O₃, less Cr₂O₃ and complex oxides, such as CrTaO₄, (Ni,Co)Al₂O₄ and Co(Al,Cr)₂O₄ were found in the oxidation scales. The scales were layered with outer (Ni,Co)O layer and inner α-Al₂O₃ layer. The innerα-Al₂O₃ layer was continuous and dense and then provided good protection. Furthermore, there were nitride precipitates in the matrix of the alloy and close to theα-Al₂O₃ layer.