M50钢表面电火花沉积Cr涂层组织结构及耐蚀性能研究

发布时间：2018-05-31 19:51

本文选题：电火花沉积 + Cr涂层　；参考：《哈尔滨理工大学》2017年硕士论文

【摘要】：Cr涂层由于其优异的抗腐蚀能力,普遍应用在金属构件的腐蚀与防护中。制备Cr涂层的方法有很多种,例如物理气相沉积、热喷涂、电镀技术及电火花沉积技术等等。电火花沉积技术由于其结合强度高、热影响区小、沉积效率高、可用于局部处理大型工件等优点,而成为一种新兴快速发展的表面处理技术。因此,本文主要通过电火花沉积表面改性技术在M50钢基体上制备Cr涂层,研究Cr涂层组织结构及耐腐蚀性能。采用电火花沉积技术在M50钢基体上制备不同工艺参数(100 V-60 μF,100V-90μF,100V-120μF,150V-60μF,150V-90μF,150V-120μF)的 Cr涂层,并对涂层的沉积规律、表面形貌、物相组成、显微结构、硬度及孔隙率进行研究。研究结果表明:不同参数Cr涂层的单位面积增重随着沉积次数增加而线性增加,最终保持相对稳定的范围内,达到极限增重;涂层表面呈现泼溅状形貌,随着电压增大,单次脉冲沉积点尺寸增大,但电容对其影响不大;涂层表层为非晶,次表层主要为超细晶α(Fe-Cr),内层为细晶γ(Fe-Cr);与基体相比,涂层的硬度发生下降,但是也能达到550 HV以上;不同沉积参数的涂层孔隙率在2%以内,当沉积参数太大或者较小时,孔隙率较大,当参数适中时,涂层孔隙率较小。在电化学测试方面,不同参数涂层的自腐蚀电位与基体相比,均增大,腐蚀倾向性降低,其中150 V-60μF参数涂层的自腐蚀电位最大,耐腐蚀性能最好。基体和涂层的电化学阻抗谱表现为一个明显加宽的容抗弧;在浸泡试验方面,基体的腐蚀速度明显大于涂层的腐蚀速度,涂层抗腐蚀能力大于基体,其中150V-60μF参数涂层腐蚀速度较小,抗腐蚀能力较好。去除表面腐蚀产物之后,基体发生明显的龟裂现象,涂层仍保持原始的泼溅状形貌;在盐雾试验方面,基体失重显著大于涂层,其中150V-60μF参数涂层的失重最少,耐腐蚀性能最好。涂层表面生成一层腐蚀产物,能够有效阻止涂层进一步发生腐蚀,去除表面腐蚀产物之后,基体表面分布许多腐蚀坑,而涂层表面平坦无腐蚀坑。由截面照片可知,基体发生严重内腐蚀,而涂层只是当纵向裂纹贯穿到基体时,腐蚀介质通过裂纹扩散到基体,使基体发生轻微腐蚀。综合上所述,根据电化学测试、浸泡试验及盐雾试验研究基体和涂层的耐腐蚀性能,研究结果表明,涂层的耐腐蚀性能显著优于基体,其中150 V-60μF参数的涂层抗腐蚀能力最强。
[Abstract]:Because of its excellent corrosion resistance, Cr coating is widely used in corrosion and protection of metal components. There are many ways to prepare Cr coating, such as physical vapor deposition, thermal spraying, electroplating technology and electrospark deposition, etc., because of its high bonding strength, small heat impact zone and high deposition efficiency, the electrospark deposition technology can be used for the local area. To deal with the advantages of large workpieces and become a new and rapidly developing surface treatment technology. Therefore, in this paper, Cr coating was prepared on M50 steel substrate by electrospark deposition surface modification technology, and the microstructure and corrosion resistance of Cr coating were studied. The different technological parameters (100 V-60) were prepared by EDM technology on the matrix of M50 steel. The Cr coating of Mu F, 100V-90 mu F, 100V-120 mu F, 150V-60 mu F, 150V-90 u F, 150V-120 um F) and Study on the deposition law, surface morphology, phase composition, microstructure, hardness and porosity of the coating. The results show that the weight gain per unit area of the coating increases linearly with the increase of the number of deposition, and finally remains relatively stable. In the range, the maximum weight gain is reached; the surface of the coating is splashed, with the increase of the voltage, the size of the single pulse deposition point increases, but the influence of the capacitance on it is little. The coating surface is amorphous, the subsurface is mainly ultrafine crystal a (Fe-Cr), the inner layer is fine crystal gamma (Fe-Cr), and the hardness of the coating decreases as compared with the matrix, but it can also reach 550 HV. The porosity of the coating with different deposition parameters is less than 2%. When the deposition parameters are too large or hourly, the porosity is larger. When the parameters are moderate, the porosity of the coating is small. In the electrochemical test, the self corrosion potential of the coating increases and the corrosion tendency decreases. The self corroding electricity of the 150 V-60 mu F coating is self corroding electricity. The electrochemical impedance spectrum of the matrix and coating shows a broad tolerance arc. In the immersion test, the corrosion rate of the matrix is obviously greater than the corrosion rate of the coating. The corrosion resistance of the coating is greater than that of the matrix, in which the corrosion rate of the 150V-60 mu F coating is smaller and the corrosion resistance is better. The removal of the corrosion resistance is better. After the surface corrosion products, the matrix has obvious crack phenomenon and the coating remains original splash shape. In the salt fog test, the weight loss of the matrix is significantly greater than that of the coating. The 150V-60 mu F parameter coating has the least weight loss and the best corrosion resistance. The coating surface generates a layer of corrosion product, which can effectively prevent the coating from further corrosion. After the surface corrosion products are removed, many corrosion craters are distributed on the surface of the substrate, and the surface of the coating is flat and no corrosion pit. It is known by the cross section photographs that the matrix has serious internal corrosion, and the coating only spreads through the crack to the matrix when the longitudinal crack runs through the matrix, which makes the matrix slightly corroded. The corrosion resistance of the substrate and coating was studied by test, immersion test and salt spray test. The results showed that the corrosion resistance of the coating was significantly better than that of the matrix, and the corrosion resistance of the coating with 150 V-60 mu F parameters was the strongest.
【学位授予单位】：哈尔滨理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4

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