预氧化对一种镍基单晶高温合金的热腐蚀影响

摘要

To understand the effect of pre-oxidation on short-term hot corrosion of nickel-based single crystal superalloys, salt corrosion method was used to study the hot corrosion behavior of a superalloy after preoxidation under Na2SO4-NaCl salt solution. The corrosion kinetics curves of different pre-oxidation treatment time of the alloy were measured, the microstructure of the cross-section of the alloy corrosion layer was observed with a scanning electron microscope (SEM), and the phase structure was confirmed by X-ray diffraction (XRD). The result showed that the alloy surface without pre-oxidation was severely corroded, hot corrosion weight gain reached the maximum mass 0. 033 mg/cm2, and the corrosion kinetic curve followed the parabolic law. After pre-oxidation treatment, the corrosion of the alloy surface was obviously improved, the hot corrosion of the alloy at 900 ℃ accorded with the model of sulfurization oxidation, and corrosion products appeared layered structure. The main corrosion products of the alloy were Ni O, Al2O3, a small amount of NiCr2O4, TiO2, NiS2, and so on, among which oxides such as Al2O3, TiO2 located on the outermost layer of the oxide layer. The pre-oxidized Al2O3 layer had a significant protective effect on short-term hot corrosion of superalloy under Na2SO4-NaCl salt film. The thickness of the etching layer was reduced from 170 μm to80 μm. A dense oxide layer could significantly prevent the diffusion of sulfur and improve the hot corrosion resistance of the tested alloy.%为了解预氧化对镍基单晶高温合金的短时热腐蚀影响, 采用涂盐法研究了一种高温合金经预氧化后在Na2SO4-NaCl盐膜条件下的热腐蚀行为, 测量了不同预氧化处理时间合金的腐蚀动力学曲线, 借助扫描电子显微镜 (SEM)观察了合金腐蚀层截面的微观组织, 并利用X-射线衍射仪 (XRD)确定相结构.结果表明:未经过预氧化处理的合金表面腐蚀严重, 热腐蚀增重质量最多达到0. 033 mg/cm2, 其腐蚀动力学曲线遵循抛物线规律, 而经过预氧化处理后合金表面腐蚀明显改善;合金在900℃下的热腐蚀符合硫化氧化模型, 腐蚀产物出现了分层结构;合金的主要腐蚀产物是Ni O、Al2O3以及少量NiCr2O4、TiO2、Ni S2等, 其中Al2O3、TiO2等氧化物位于氧化层最外层;预氧化生成的Al2O3层对高温合金在Na2SO4-NaCl盐膜下的短时热腐蚀有明显的保护作用, 腐蚀层厚度从170μm降低至80μm.致密的氧化物保护层能够显著阻止硫元素的扩散, 提高合金的耐热腐蚀性能.