【作者】 史莹；

【导师】 陈岁元； 刘常升；

【作者基本信息】 东北大学 ， 材料学， 2008， 硕士

【摘要】 化学镀镍方法以其工艺简便、成本低、镀层厚度均匀、可大面积镀覆等优点,已广泛应用于实际生产中,然而,随着技术不断发展与实际生产工程中需要,又逐步发展具有特定功能的复合镀层。利用纳米材料的一些独特的性能,结合传统表面技术制备表面纳米颗粒增强复合镀层的研究成为当今材料表面领域的热点课题之一。本文结合这两项技术的特点,在45#钢表面化学镀层中复合纳米Al2O3粒子和PTFE粒子,研究制备具有高耐磨和自润滑性能的化学复合镀技术,以满足企业实际生产的需要。主要运用显微硬度计、金相显微镜、SEM、XRD和摩擦磨损试验机等检测手段对实验样品的组织结构、表面形貌、显微硬度、耐磨性能及其机理进行了系统研究,结果表明：实验优化出的化学镀配方为：硫酸镍25g/L,次亚磷酸钠30g/L,乳酸25ml／L,柠檬酸5g/L,乙酸钠15g/L,氨基乙酸3g/L,硫脲3～5mg/L,pH=4.8,温度88±2℃；纳米A1203的加入量为2-3g/L,PTFE乳液的加入量为10ml／L。利用优化了的制备技术,在45#钢表面成功制备出具有纳米A1203增强、PTFE复合减摩的高耐磨和低摩擦系数的Ni-P-Al2O3-PTFE复合镀层。实验制备的Ni-P、Ni-P-Al2O3、Ni-P-PTFE和Ni-P-Al2O3-PTFE等镀层镀态时为非晶态结构,Ni-P非晶态镀层硬度为516HV,Ni-P-PTFE非晶态镀层的硬度为380HV,Ni-P-Al2O3非晶态镀层硬度为684HV,Ni-P-Al2O3-PTFE非晶态镀层的硬度为452HV。经过热处理后镀层在300℃时开始晶化,到400℃时其镀层全部转化为晶态；Ni-P合金镀层的硬度经过400℃热处理后达到最大值894HV；Ni-P-Al2O3复合镀层400℃热处理后达到最大值1215HV；因为PTFE的熔点为327℃,Ni-P-Al2O3-PTFE多元复合镀层375℃处理的硬度是894HV,400℃处理的硬度是1187HV,镀层的硬度大幅提高,证明镀层中PTFE的气化逸出,蒸发温度是375℃,使镀层的自润滑性能降低,因此本实验选择350℃热处理一小时,可以得到相对较高的硬度756HV,同时不会破坏镀层中的PTFE。制备的Ni-P-Al2O3-PTFE镀层经过350℃×1h热处理后其磨损量为1.6mg,摩擦系数为0.11,表现出了优良的综合耐磨性能。Ni-P-Al2O3-PTFE复合镀层中,高硬度的纳米Al2O3通过复合沉积与镍磷镀层构成复合相,提高了镀层的硬度及耐磨性能；而PTFE粒子由于具有良好的自润滑性能,复合镀层在受到摩擦时,PTFE粒子可通过自身的层状剥始在镀层表面铺展,形成连续的减磨膜,降低了复合镀层摩擦系数；二者协同作用使Ni-P-Al2O3-PTFE复合镀层具有高的耐磨性能和自润滑性能。更多还原

【Abstract】 Electroless Nickel Plating(ENP) have been widely applied in production with its advantages such as simple processing, low-cost, uniformity, thickness and large-area plating. However, with the technology development and actual production’s needs, composite coatings were gradually developed with their specific functions. Using some of the unique performance of nano-materials, combining traditional surface technology so as to prepare nanoparticles reinforced surface coating of composite materials become one of the hot topics in the surface area. This paper studied the preparation of a kind of coating on 45 steel surface with the performance of high wear resistance and self-lubricating that compounded with nano-Al2O3 powder and PTFE, so as to meet the needs of actual production.The microstructure, surface morphology, hardness, wear resistance and also formation mechanism of the test samples were systematic studied by Micro-hardness tester, Optical Microscope, Scanning Electron Microscope, X-ray diffraction and Friction-Wear tester. The results show as follow:The optimized dispensation of electroless plating of nikel through the experiments are showed as follows:NiSO4 25g/L, NaH2PO2 30g/L, CH3CH(OH)COOH 25ml/L, CH3COONa 15g/L, C2H5NO2 3g/L, CH4N2S 3-5mg/L; pH=4.8, the temperature is 88±2℃; The addition of nano-Al2O3 was 2-3g/L, the addition of PTFE emulsion was 10ml/L. Using the optimized technology, the Ni-P-Al2O3-PTFE composite coating with nano-Al2O3 enhanced, PTFE antifriction of high wear-resistant and low coefficient on the 45 steel surface was successfully prepared.The prepared coating of Ni-P、Ni-P-Al2O3、Ni-P-PTFE and Ni-P-Al2O3-PTFE after plating was non-crystalline, the hardness were followed by 516HV,684HV,380HV and 452HV. The plating coating became crystalline after heat treatment temperature at 300℃, and totally crystalline at temperature 400℃. The maximum hardness of Ni-P coating achieved to 894 HV after 400℃heat treatment; Ni-P-Al2O3 composite coating achieved up to 1215 HV also after heat treatment at 400℃. Because the melting point of PTFE is 327℃, the hardness of Ni-P-Al2O3-PTFE multiple composite coatings after heat treatment at 375℃was 894 HV and 1187 HV at 400℃, which illuminated PTFE in coating had gasified and escaped at evaporation temperature 375℃, so the self-lubricating properties reduced. Thus this paper choose the heat treatment temperature at 350℃for one hour, then the hardness can be relatively achieved up to 756 HV and will not damage PTFE in the coating. The wear performance showed that, the wear rate of Ni-P-Al2O3-PTFE multiple composite coatings was reduced evidently, and had lower friction coefficient. The wear resistance of Ni-P-Al2O3-PTFE multiple composite coating was the best after heat treatment of 350℃for 1h, the wear losses was 1.6mg and the friction coefficient 0.11.In the Ni-P-Al2O3-PTFE multiple composite coatings, as a kind of hard particle, Al2O3 particles and nickel-phosphorus coating form a complex phase through composite deposition. The hard particles greatly enhance the property of the coating hardness and wear-resistance. The PTFE particles have nice property of self-lubricating, when they were rubbed, they enabled to form a spreading layer by the lamellar delamination in the coating containing PTFE, so the uniform thickness anti-resistance layer was formed on the samples surface to reduce the friction coefficient and wear losses. The co-action of both particles enabled the Ni-P-Al2O3-PTFE coating with properties of high wear resistance and self-lubricating.更多还原