【作者】 张关震；

【导师】 贺定勇；

【作者基本信息】 北京工业大学 ， 材料科学与工程， 2011， 硕士

【摘要】 本文从非晶/纳米晶合金成分设计出发,研究了B元素对Fe-Cr-B-C-Si合金系非晶相含量及纳米晶晶粒尺寸的影响机制及规律;建立了非晶相含量、纳米晶粒尺寸与涂层显微组织形貌等微结构特征的影响关系,并研究了非晶/纳米晶涂层的磨粒磨损与腐蚀行为及其相应的失效机理。主要研究结果如下:在一定范围内,通过调整粉芯丝材中B元素含量,采用电弧喷涂方法制备了五组不同非晶相含量、纳米晶粒尺寸的Fe基非晶/纳米晶涂层。涂层由变形良好的扁平化粒子相互搭接堆积而成,呈典型的层状结构形貌,结构致密,通过图像分析软件测量涂层孔隙率约在3%左右。其中Fe₅₆Cr₁₅B₂₆（CSi）₃合金具有相对最高的非晶相含量、最小的纳米晶粒尺寸,其非晶含量可达36.4%,纳米晶粒尺寸为12.4nm。所制备的涂层均具有较好的热稳定性,差热分析结果表明在760K以下使用涂层不会发生晶化。制备的非晶/纳米晶涂层均具有较高的硬度,维氏硬度值保持在865¹166HV0.1。涂层在室温下的耐磨粒磨损性能约为基体Q235钢的6¹3倍,主要磨损机制以疲劳磨损为主。随涂层中纳米晶粒尺寸的减小和非晶相含量的增加,涂层的维氏硬度逐渐提高,耐磨粒磨损性能相应增加。涂层在经过923K两个小时的退火处理后,其维氏硬度和相对耐磨性均得到提升,保持了良好的热稳定性。制备的非晶/纳米晶涂层在室温3.5%NaCl溶液中的电化学结果与基体相比均具有较高的自腐蚀电位,呈现相对较好的抗氯离子腐蚀能力,能够很好的对基体起到保护作用。腐蚀行为以点蚀为主同时兼有均匀腐蚀的进行。对合金成分差别较大的Fe₆₂Cr₁₅B₂₀（CSi）₃、Fe₅₆Cr₁₅B₂₆（CSi）₃两涂层对其进行高温腐蚀的研究,结果表明,在923K经过100h的高温腐蚀后,其高温氧化动力学曲线和涂盐（Na₂SO₄+K₂SO₄）热腐蚀动力学曲线均呈抛物线状,最终两涂层的氧化增重量稳定在6mg/cm²左右,涂盐热腐蚀增重量约为10mg/cm²,均明显优于基体材料,呈现相对较好的抗高温氧化和热腐蚀性能。两涂层高温氧化和涂盐热腐蚀后的表面产物均为Fe₂O₃和尖晶石FeCr₂O₄氧化物,由这些氧化物在涂层表层所构成的均匀致密的钝化膜有效的保护了涂层内部组织。更多还原

【Abstract】 In this study the effect of boron addtion on the Fe-Cr-B-C-Si amorphous alloy’s amorphous content and nanocrystalline grain size during arc spraying process was invistigated based on the design amorphous/nanocrystalline alloy system. The relationship between amorphous content, nanocrystalline grain size and microstructure of the coatings was established, the corrosion and abrasive wear behavior of the amorphous/nanocrystalline alloy coatings were studied in details. The major results are summarized as follows:Fe-based coatings with different amorphous content and nanocrystalline grain size were prepared by arc spraying technology by adjusting the boron content in certain exten. The coating consisted of numerous flattened lamellae parallel to the substrate. The porosity was measured by the image analysis software and the value was about 3%. It was found that the optimum boron content in the alloy for the most amorphous content and nanocrystallin grain size was 26at%. The highest amorphous content was about 36.4%; and the smallest nanocrystalline grain size was 12.4 nm. With this composition the alloy possessed high thermal stability as the crystallization temperature exceeded 760K.It was found that the coatings possessed higher value of microstruture in the range of 865¹166HV0.1. The coatings abrasive wear resistance was 6¹3 times higher than that of the Q235 mild steel. In addition, fatigue abrasion form was observed on the surfaces of the coatings during abrasion testing processes. The wear resistance and hardness improved with the higher amorphous content and lower nano-grain size. The coatings annealed at the temperature of 923K expressed the greated thermal stability with relativly higher mircohardness and wear resistance. The amorphous/nanocrystalline alloy coatings showed excellent corrosion resistance in 3.5% NaCl solution, which were much better than Q235 mild carbon steel. Testing results shows that main corrosion mechinanism of coatings were pitting corrosion and uniform corrosion. Fe₆₂Cr₁₅B₂₀（CSi）₃ and Fe₅₆Cr₁₅B₂₆（CSi）₃ coatings after high-temperature corrosion at 923K for 100h, both the oxidation kinetics and the molten salt thermal etching kinetics showed a parabolic relationship. The coatings possess of high oxidation and thermal etching resistance with a final weight gain of 6mg/cm² and 10mg/cm² for each condition. Most of the products after high temperature oxidation and thermal etching were Fe₂O₃ and FeCr₂O₄. The existence of the passive film consist of these oxides gave a protection to the inner coating.更多还原