【作者】 屈文娟；

【导师】 杨世伟；

【作者基本信息】 哈尔滨工程大学 ， 材料学， 2011， 硕士

【摘要】 为满足超超临界汽轮机叶片的工况需求,本文采用料浆法在1Cr11MoNiW1VNbN不锈钢表面制备了Al-Si涂层。依据GB/T13303-91《钢的抗氧化性能测定方法》和HB5258-2000《钢及高温合金的抗氧化性能测定试验方法》标准,对制备Al-Si涂层的试样和无涂层试样制定了高温氧化试验：温度为700℃、保温时间为1000h的恒温氧化试验；温度为700℃、冷热循环11次的循环氧化试验。利用扫描电镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)等分析检测手段对Al-Si涂层的表面形貌、成分、组织结构及涂层开裂和剥落的成因进行了分析和研究。制备的Al-Si涂层分为外层、金属间化合物层和过渡层三层。外层富铝层的厚度约为8μm,主要成分是a-Al和少量的FeAl3相；金属化合物层的厚度约为16μm,主要成分为Fe2A15相；过渡层约为14μm,因接近基体组织以a-Fe和Fe3A1相为主。金属化合物层是抗高温氧化的有效保护层,该层致密、厚度均匀、与基体结合界面平整且结合良好。试验结果表明,Al-Si涂层700℃恒温氧化1000h表面形成致密、连续的a-A1203保护性氧化膜。氧化初期生成PBR>1的FeAl2O4和FeO氧化物导致膜内产生的压应力,后期阶段氧化膜由θ-Al2O3向α-Al2O3转变时产生的拉应力,以及涂层内的孔洞均会造成表面氧化膜开裂和剥落。但是涂层由FeAl3相、Fe2A15相向FeAl相的转变,可以为表层提供足够的Al元素来不断形成Al2O3氧化膜,涂层具有良好的自修复能力。涂层中的Si元素可以有效控制脆性相Fe2Al5的生长,改善Al2O3氧化膜塑性,促进β相向γ’相的转变,降低渗铝层的脆塑性转变温度,增强渗层的吸附能力；Si与合金元素生成的第二相能有效阻碍涂层与基体元素的互扩散,提高涂层的抗高温氧化性能。依据GB/T13303-91和HB5258-2000标准对Al-Si涂层和无涂层试样进行高温氧化性能评定：无涂层试样为抗氧化等级,Al-Si涂层属于完全抗氧化等级。对比分析恒温氧化动力学曲线和循环氧化动力学曲线,Al-Si涂层的抗高温氧化性能优于无涂层试样。更多还原

【Abstract】 In this paper, Al-Si coating was prepared on 1Cr11MoNiW1VNbN stainless steel by slurry process to improve application temperature of ultra steam turbine blades. According to the criterion of GB/T13303-91 and HB5258-2000, the isothermal oxidation testing at 700℃in air for 1000h and oxidized circularly at 700℃for 11 times was carried out.The composition, structure, surface morphology and the failure causes of Al-Si coating were analysised and researched by the analysis and detection methods of SEM, EDS, XRD and so on.The Al-Si coating prepared by slurry process includes outer layer, intermetallic compound layer and transition layer.The Al-rich outer layer mainly contains the phase ofα-Al and few FeAl3, whose thickness is about 8μm. The metal compound layer is about 16μm. and the main component is the Fe2Al5 phase.The transition layer is about 14μm and its composition approach to the matrix organizations.The Metallic compound layer is the effective protection against high temperature oxidation,which is dense, uniform, smooth and consolidated well.The results indicated that, the dense and continuous oxide films ofα-Al2O3 with a certain thickness formed on the surface of Al-Si coating at 700℃for 1000h were the barriers in the high temperature oxidation.The oxides of FeAl2O4 and FeO generated in the early oxidation produce compressive stress,while the transition fromθ-Al2O3 toα-Al2O3 produces tensile stress in oxide film.Those stresses and the holes in the coating will cause oxide film cracked and spalled.But the enough Al element provided by phase transition from FeAl3 and Fe2Al5 to FeAl can keep the repaired formation of the oxide film itself. Si elements in the coating can effectively control the growth of brittle phase, improve the plastic of Al2O3, promote phase transition fromβtoγ’, reduce the brittle-plastic transition temperature and increase the adsorption capacity of coating;The second phase particles formed by Si and alloying elements can effectively hind interdiffusion of the coating and substrate alloying elements, and the performance of high temperature oxidation resistance of the coating is improved.Assessing by the standards of GB/T13303-91 and HB5258-2000, Al-Si coating is completely antioxidant, and the oxidation rate was significantly lower than uncoated samples.The Al-Si coating has a better ability than uncoated samples in the high temperature oxidation and cyclic oxidation.更多还原