316L不锈钢晶粒尺寸对ZDDP摩擦反应膜生长的影响

发布时间：2018-04-26 14:47

  本文选题：ZDDP + 摩擦反应膜　； 参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：二烷基二硫代磷酸锌(ZDDP)是一种应用广泛的汽车润滑油添加剂,常用于发动机活塞环。ZDDP会在摩擦过程中界面处发生分解,形成的摩擦反应膜通过减小钢铁或其它对磨材料表面的金属与金属之间的接触起到保护表面的作用。因为ZDDP在使用时,不仅会使摩擦损耗增加,而且会产生含Zn、P、S的化合物,磷酸锌和其他的含磷的沉淀物会使三元催化器中毒,而且会影响氧气传感器,降低催化转换器的使用效率和寿命。但现在还并未很好的理解摩擦反应膜的生长机制,限制了研究人员进一步开发具有替代性的并且性能更加优异的添加剂。本文为研究ZDDP摩擦反应膜的生长机制,利用超声冷锻技术(UCFT)、真空退火技术,分别在钢材表面制备了纳米化层及不同晶粒尺寸样品。利用CSM摩擦磨损试验机考察了不同晶粒尺寸的钢材表面分别在聚α烯烃合成油(PAO4)和含1.0 wt%二烷基二硫代磷酸锌(ZDDP)润滑条件下的摩擦磨损行为。利用扫描电子显微镜、金相显微镜、三维白光表面形貌仪、X射线衍射仪、显微硬度计等微观检测设备分析了纳米化层的微观形貌、组织结构和显微硬度等。利用原子力显微镜(AFM)对单微凸体滑动界面上ZDDP分解的摩擦反应膜的生长与性质进行原位分析。研究结果表明:(1)在316L不锈钢表面制备的纳米晶层,最表层平均晶粒尺寸约为12.7nm,表面硬度由190 HV提高到341 HV。真空退火处理后,晶粒尺寸变大。UCFT样品硬度最高,摩擦系数和磨损率最小。晶粒的细化有助于使摩擦磨损降低。(2)在单微凸体滑动实验中,随着滑移次数增加,ZDDP摩擦反应膜生长,成核位置随机分布,探针持续滑动促进了反应膜的生长。摩擦反应膜具有粗糙、斑块状、板状等形状特征。UCFT样品成膜比Untreated样品成膜速度更快。相同滑移次数时,UCFT样品成膜区域高度更高。这可能是因为纳米化处理后表面存在大量的晶界,样品表面晶粒尺寸变小,晶粒细化并且晶界处的原子密度较低,容易产生更多的断键,从而提高表面活性,促进磨损表面吸附膜或反应膜的形成。(3)单微凸体滑动实验样品表面成膜区域有Zn、P、S等特征元素出现,未成膜区域则没有,说明ZDDP在摩擦磨损过程中发生了分解,生成了磷酸盐摩擦反应膜,起到了抗磨作用。
[Abstract]:Zinc dialkyl dithiophosphate (ZDDP) is a widely used additive for automotive lubricating oil, which is often used in the decomposition of the interface between the piston ring of engine and ZDDP during friction. The formed friction reaction film protects the surface by reducing the contact between metal and metal on the surface of grinding material. Because when ZDDP is used, it not only increases the friction loss, but also produces compounds containing ZnPPU S, zinc phosphate and other phosphorous precipitates can poison ternary catalytic converters and affect oxygen sensors. Reduce the efficiency and lifetime of the catalytic converter. However, the mechanism of friction film growth has not been well understood, which limits the researchers to further develop alternative and better performance additives. In order to study the growth mechanism of ZDDP friction reaction film, nanocrystalline layers and samples of different grain sizes were prepared on the surface of steel by ultrasonic cold forging technique and vacuum annealing technique. The friction and wear behaviors of steel surfaces with different grain sizes under the lubrication conditions of polyolefin synthetic oil (PAO4) and zinc dialkyldithiophosphate (ZDDP) containing 1.0 wt% dialkyl dithiophosphate were investigated by CSM friction and wear tester. The microstructure, microstructure and microhardness of the nanocrystalline layer were analyzed by means of scanning electron microscope, metallographic microscope, three dimensional white light surface topography analyzer and microhardness tester. The growth and properties of friction reaction film decomposed by ZDDP on the sliding interface of a single convex body were analyzed in situ by atomic force microscopy (AFM). The results show that the average grain size of the nanocrystalline layer on the surface of 316L stainless steel is about 12.7 nm, and the surface hardness is increased from 190 HV to 341 HV. After vacuum annealing, the grain size becomes larger. The hardness of UCFT sample is the highest, and the friction coefficient and wear rate are the smallest. The grain refinement is helpful to reduce the friction and wear. 2) in the sliding experiment of single microconvex body, with the increase of slip times, the ZDDP friction reaction film grows, the nucleation position is randomly distributed, and the continuous slippage of the probe promotes the growth of the reaction film. The friction reaction film has the characteristics of rough, patch and plate shape. The film forming rate of UCFT sample is faster than that of Untreated sample. The film forming area of UCFT samples is higher than that of UCFT samples with the same slip times. This may be due to the existence of a large number of grain boundaries on the surface after nanocrystalline treatment. The grain size on the surface of the sample becomes smaller, the grain size is fine and the atomic density at the grain boundary is lower, which makes it easy to generate more broken bonds, thus increasing the surface activity. Promoting the formation of adsorbed or reactive film on wear surface. (3) there are characteristic elements such as ZnPU S in the film forming region of monomicroconvex sliding samples, but not in the unformed film region, which indicates that ZDDP decomposes during friction and wear. A phosphate friction reaction film was formed, which played an anti-wear effect.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4
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本文编号：1806482