环境湿度条件下聚晶金刚石对磨氮化硅的摩擦化学机理研究

发布时间：2018-04-30 07:27

本文选题：相对湿度 + 表面悬键钝化　；参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：聚晶金刚石(PCD)具有高硬度、高耐磨性以及优异韧性,可用于地质钻探、刀具切削等领域,在钻探的过程中很难保证PCD处于良好的液体润滑条件下,此时湿度气氛会严重影响钻进或切削性能,界面间的摩擦化学效应会对材料的磨损有重要影响。故本文考察了PCD在相对湿度水平(RH)为5%-85%以及水润滑条件下对磨氮化硅球的摩擦学行为。采用光学显微镜、三维形貌、Raman、SEMEDS、XPS以及AFM等分析测试手段,分析研究表面化学悬键钝化效果、碳原子重杂化、界面碳质转移膜的形成以及氧化摩擦化学反应对PCD摩擦学性能的影响,研究结果如下:(1)在5%-50%RH条件下,Si3N4球表面碳质转移膜的形成是影响稳态摩擦系数的主要因素,在5%RH条件下,较长的跑合期~4000周保证了连续的及均匀的碳质转移膜的形成,能够显著降低滑移界面间的粘着相互作用,最终获得超低稳态时的摩擦系数~0.04。在相对湿度为10%-50%RH时,测试环境中有足够的水分子浓度,通过形成-H、-OH、H2O钝化表面抑制了碳质转移膜的形成。对于PCD的磨损,在湿度为5%RH条件下获得PCD最大的磨损率~9.1×10-11mm3/Nmm。(2)在高湿度(55%-85%RH)条件下,测试环境中高浓度的水分子经物理作用吸附于滑移的界面,在界面间通过毛细冷凝作用形成液桥,在滑移界面施加了弯月面力,最终获得了不稳定且最高的摩擦系数值~0.105。但在水润滑条件下,获得最低的摩擦系数~0.06。水润滑时易在滑移界面形成有效的水分子润滑膜,显著降低界面间的摩擦力。在高湿度条件(55%-85%RH)下,Si3N4形成了不同的磨斑大小,随着相对湿度的增加,对磨球的磨斑直径逐渐增加,在湿度水平为85%条件下获得最大的磨斑,然而在水润滑条件下获得最小的磨斑。(3)化学悬键钝化效果影响滑移界面间的共价相互作用,不同湿度条件对应不同的长度的跑合期,较长的跑合期是保证形成连续性好、均匀、稳定的碳质转移膜的直接原因。这种在滑移界面间有效的、连续的碳质转移膜的形成是PCD在稳态期表现出超低摩擦系数的最主要的原因。在55%-85%RH条件下,不同的Si-N/Si-OH+Si-O、Si-OH/Si-O控制Si3N4材料的氧化磨损程度。
[Abstract]:Polycrystalline diamond (PCD) has high hardness, high wear resistance and excellent toughness. It can be used in geological drilling, cutting tools and other fields. It is difficult to ensure that PCD is in good liquid lubrication condition during drilling. At this time, the humidity atmosphere will seriously affect the drilling or cutting performance, and the tribochemical effect between the interface will have an important impact on the material wear. Therefore, the tribological behavior of PCD in grinding silicon nitride balls under the condition of relative humidity of 5- 85% and water lubrication has been investigated. The effects of surface chemical hanging bond passivation, carbon atom heavy hybridization, interfacial carbon transfer film formation and oxidation tribological reaction on the tribological properties of PCD were studied by means of optical microscope, Ramana SEMEDS XPS and AFM. The results are as follows: (1) the formation of carbon transfer film on the surface of Si _ 3N _ 4 sphere under 5%-50%RH is the main factor affecting the steady friction coefficient. Under 5%RH condition, the formation of continuous and uniform carbon transfer film is ensured by a longer running period of 4000 weeks. The adhesion interaction between the slip interfaces can be significantly reduced, and the friction coefficient of 0.04 at the ultra-low steady state can be obtained. When the relative humidity is 10%-50%RH, there are enough water molecules in the test environment, and the formation of carbon transfer film can be inhibited by forming the passivated surface of H _ (-) -O _ (H _ (2)) _ (2) H _ (2) H _ (2) O. For the wear of PCD, under the condition of 5%RH, the maximum wear rate of PCD is 9.1 脳 10 ~ (-11) mm ~ (3 / Nmm 路N ~ (-2). Under the condition of high humidity ~ (55 ~ 85), the high concentration of water molecules in the test environment is physically adsorbed on the slip interface, and the liquid bridge is formed by capillary condensation between the interfaces. When the meniscus force is applied at the slip interface, the unstable and the highest friction coefficient of 0.105 is obtained. But under the condition of water lubrication, the lowest friction coefficient is 0.06. It is easy to form an effective water molecular lubricating film at the slip interface during water lubrication, which reduces the friction between the interfaces significantly. Under the condition of high humidity, Si _ 3N _ 4 forms different grinding spots. With the increase of relative humidity, the diameter of grinding spot on grinding ball increases gradually, and the largest spot is obtained at the humidity level of 85%. However, under the condition of water lubrication, the minimum wear spot is obtained.) the passivation effect of the chemical hanging bond affects the covalent interaction between the slip interfaces. Different humidity conditions correspond to different running periods of different lengths, and the longer running time is to ensure good continuity and uniformity. The direct cause of stable carbon transfer membranes. The formation of a continuous carbon transfer film between slip interfaces is the main reason for the ultra-low friction coefficient of PCD during the steady-state period. Under the condition of 55%-85%RH, the oxidation wear degree of Si3N4 is controlled by different Si-N/Si-OH Si-O Si-OH / Si-O.
【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】：TQ163

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