高温氧化是限制镍基高温合金服役寿命的主要因素之一。本工作旨在通过调控Al含量来提升Ni20Cr合金的抗氧化性能。采用机械合金化(MA)和放电等离子烧结(SPS)的方法制备了Al含量(质量分数)分别为1.5%、3.0%、5.0%的Ni20Cr-xAl合金，对比研究了SPS制备合金与相同成分铸态合金在900℃空气中的高温氧化行为。结果表明，SPS制备合金成分、组织均匀且晶粒细小，大量晶界显著加速了元素的扩散，在Al含量为1.5%时，Al内氧化严重，Cr快速外氧化生成含有大量孔隙和裂纹的Cr₂O₃膜，而在Al含量为3.0%和5.0%时，形成了保护性的连续致密的α-Al₂O₃薄膜，合金内部弥散的Al₂O₃颗粒为外Al₂O₃膜提供了形核位点并起到了钉扎作用，因此2者表现出优异的抗氧化性能，氧化速率分别为1.06 × 10^-7和4.92 × 10^-8 mg²/(cm⁴·s)。铸态合金都发生了内氧化，而且无法形成连续的外Al₂O₃膜，氧化膜的主要成分为疏松多孔的Cr₂O₃，因而氧化速率快且发生了氧化膜开裂和剥落。

As a high-performance structural material, nickel-based superalloy has excellent comprehensive properties, such as high-temperature mechanical properties, thermal stability, and corrosion resistance. It is widely used in hot-end parts, including the combustion chamber, turbine blades, and turbine disks, among others. Due to severe working environments, oxidation has become a major life-limiting factor for the nickel-based superalloy. However, the high-temperature oxidation behavior of a superalloy is complex, related to many factors, such as chemical composition and preparation technology. Many advances have been achieved through improving alloy compositions to meet the anti-oxidation requirements, and others have been accomplished using major innovations in processing. As a new powder metallurgy technology, spark plasma sintering (SPS) has the advantages of a fast heating rate, low sintering temperature, and short sintering time. However, there are few studies on the oxidation behavior of alloys prepared by this technology. In this study, Ni20Cr-xAl alloys with Al content (mass fraction) of 1.5%, 3.0%, and 5.0% were prepared by mechanical alloying and SPS. Oxidation kinetics, XRD, SEM, and TEM were used to compare and investigate the isothermal oxidation behaviors of the SPSed and the as-cast alloys with the same composition in air at 900^oC. Results indicate that the SPSed alloys have uniform microstructures and fine grains, and abundant grain boundaries significantly accelerate the diffusion of elements. When the Al content is 1.5%, severe internal oxidation of Al occurs, and a Cr₂O₃ scale containing large pores and cracks is formed due to rapid external oxidation of Cr. Al₂O₃ particles dispersed in the alloy serve as nucleation sites for the exterior Al₂O₃ scale and have a pinning effect. However, when the Al content reaches 3.0% and 5.0%, a protective, continuous, and dense α-Al₂O₃ thin scale emerges. Therefore, both alloys display excellent oxidation resistance, the oxidation weight gain is 0.25 and 0.20 mg/cm², respectively, and the corresponding oxidation rate is 1.06 × 10^-7 and 4.92 × 10^-8 mg²/(cm⁴·s). Internal oxidation occurs in all the as-cast alloys, and no continuous external Al₂O₃ scale can be formed. The main component of the oxide scales is porous Cr₂O₃, which results in high oxidation rates and crack and spallation of the oxide scales.