【作者】 吴波；

【导师】 古乐；

【作者基本信息】 哈尔滨工业大学 ， 机械设计及理论， 2019， 博士

【摘要】 降低润滑介质的粘度有助于减小全膜润滑条件下的粘性耗散,但是会增加动压润滑薄膜破裂的风险。因此,在低粘度介质润滑条件下,更多的峰峰接触可能发生,且接触强度更高,从而导致更严重的边界磨损。润滑介质本身或者添加剂往往会在摩擦界面形成具有一定承载能力的边界吸附层（不同于体相的类固体薄膜）,帮助减小峰峰接触强度,甚至阻止局部的峰峰接触。吸附层的结构特性（如厚度、可压缩性、吸附/组装强度等）决定其承载能力。本文以聚萘磺酸盐（poly（naphthalene sulfonate）,PNS）、聚醚接枝聚羧酸盐（poly（carboxylate ether）,PCE）和挂式四氢双环戊二烯(JP-10,C₁₀H₁₆)三种工业上重要的摩擦学材料为研究对象,研究其在低粘度介质及界面改性条件下的边界吸附与边界摩擦行为。为了揭示阳离子价位(单价K⁺vs二价Ca²⁺)和Ca²⁺离子浓度对PNS边界吸附层结构和吸附层之间相互作用的影响,分别在0.1 M K₂SO₄、0.1 M Ca（NO₃）₂和5 mM Ca（NO₃）₂背景溶液中研究了PNS在云母表面的边界吸附行为。研究发现:二价的Ca²⁺离子比单价的K⁺离子具有更强的能力组装PNS发展多层吸附;Ca²⁺离子能桥接PNS吸附层,而K⁺离子不能;增加Ca²⁺离子浓度能有效促进更多的PNS分子组装更厚的吸附层,但不改变吸附层之间的桥接强度。为了揭示分子结构对PCE吸附层结构的影响以及实验地显示Ca²⁺离子桥接机理,分别在0.1 M K₂SO₄和0.1 M K₂SO₄+饱和Ca（OH）₂背景溶液中研究了多种分子结构相似但具体分子结构参数不同的PCE在云母表面的边界吸附行为;为了模拟实际胶体悬浮液系统条件,以二氧化硅作基底表面,在0.1 M K₂SO₄+饱和Ca（OH）₂的近胶体悬浮液中研究了PCE的边界吸附行为。研究发现:分子结构参数影响PCE的吸附性;PCE在高钙水溶液中不吸附于负电的云母或者二氧化硅表面。根据分子结构特性,分析了JP-10在金属表面的吸附机理和吸附形态;为了揭示JP-10吸附对摩擦行为的影响,在载荷1.5 GPa/3.8 N、滑动速度100 mm/s（时间7200 s）的测试条件下,比较了大气、室温环境中干摩擦、去离子水、JP-10和专业4050航空润滑油润滑条件下M50钢相对Si₃N₄球滑动的边界摩擦行为;为了探索JP-10边界吸附层的承载特性,恒定滑动速度100 mm/s,在0.7–2.3 GPa/0.39–13.8 N的载荷条件下,比较了去离子水、JP-10和4050油润滑条件下M50钢相对Si₃N₄球滑动的边界摩擦行为;为了探索JP-10的动压润滑能力,恒定载荷1.5 GPa/3.8 N,在10–2500 mm/s的滑动速度范围内,比较了去离子水、JP-10和4050油润滑条件下M50钢相对Si₃N₄球滑动的摩擦行为。研究发现:JP-10具有一定的边界和动压润滑能力,但显著弱于专业润滑油。为了探索JP-10介质中金属/陶瓷摩擦副的表面摩擦学改性方法,分别在M50钢表面沉积银膜、合金化银膜、注氮、沉积TiAlN涂层和合金化Ta涂层,然后在JP-10介质中测试了这些改性表面在一系列载荷条件下相对Si₃N₄球滑动的边界摩擦磨损性能。研究发现:相比原始表面,硬质的改性表面在JP-10介质中展现了显著改善的边界摩擦和磨损特性。本文的研究工作揭示了低粘度介质条件下PNS、PCE和JP-10分别与特定表面之间的相互作用及其吸附层结构特性以及吸附层之间的相互作用,为其分子结构设计与优化以及相关表面摩擦学设计提供了依据;同时,也为基于定制的摩擦学表面边界吸附层/薄膜提供了亚纳米级精度（原子/分子水平）的表征方法。更多还原

【Abstract】 Lowering the viscosity of lubricating media contributes to reducing viscous dissipation under full-film lubrication,but increases the risk of breakdown of hydrodynamic lubricating films.Under the lubrication of low-viscosity media,it is very likely that more asperities will come into direct contact and the contact strength will become higher,thereby resulting in severer boundary wear.Lubricating media and/or additives usually adsorb onto friction surfaces to form a solid-like film different from the bulk phases.The boundary adsorption layers possess certain load-carrying capacity and can help reduce asperity-to-asperity contact strength,even prevent local contact.The load-carrying capacity of a boundary adsorption layer is intimately dependent on its structural properties（e.g.,thickness,compressibility and adsorption/assembly strength）.In this dissertation,three industrially important tribological materials,poly（naphthalene sulfonate）（PNS）,poly（carboxylate ether）（PCE）and JP-10(C₁₀H₁₆),were employed and their boundary adsorption and boundary tribological behaviors were investigated in the conditions of low-viscosity media with active agent and interface modification.To reveal the effects of ionic valence(monovalent K⁺vs divalent Ca²⁺)and Ca²⁺ion concentration on structural properties and interations between adsorption layers,PNS’s boundary adsorption behaviors on mica were comparatively studied in0.1 M K₂SO₄ and 0.1 M Ca（ON₃）₂ as well as 5 mM Ca（ON₃）₂ solutions.It was found that divalent Ca²⁺ions possessed stronger capacity of assembling PNS molecules to develop multi-layer adsorption than monovalent K⁺ions and that Ca²⁺ions can bridge the opposing PNS films while K⁺ions cannot.Furthermore,increasing Ca²⁺ion concentration can effectively promote more PNS molecules to assemble a thicker adsorption layer,but cannot strengthen the bridging.To reveal the effect of molecular structure on structural properties of PCE adsorption layers and experimentally show the Ca²⁺ion bridging mechnism,boundary adsorption behaviors of various PCEs on mica were comparatively studied in 0.1 M K₂SO₄ and 0.1 M K₂SO₄ with saturated Ca（OH）₂.These PCEs shared a similar molecular configuration,but had different specific molecular structural parameters.To more closely mimic actual colloidal suspension system conditions,silica was also used as the substrate surfaces in the experiments carried out in Ca（OH）₂-saturated 0.1 M K₂SO₄ solution with and without PCE.The studies revealed that specific molecular structural parameters can modify PCE’s adsorption and that PCE did not adsorb onto negatively charged mica or silica in high-calcium aqueous conditions.Adsorption mechanism and conformation of JP-10 on metal surfaces were analyzed according to molecular structure properties.To show the effect of JP-10adsorption on friction,boundary tribological behaviors of M50 bearing steel sliding against a Si₃N₄ ball were comparatively investigated under dry friction,in deionized water,in JP-10 and in professional aviation engine lubricating oil（4050 oil）at a load of 1.5 GPa/3.8 N and a sliding speed of 100 mm/s for 7,200 s at room temperature in ambient atmosphere.To show the load-carrying properties of JP-10boundary adsorption layer,friction tests were further perfomed in deionized water,JP-10 and 4050 oil under a variety of load conditions of 0.7–2.3 GPa/0.39–13.8 N at the constant sliding speed 100 mm/s,respectively.To evaluate the hydrodynamic lubrication capacity of JP-10,friction tests were also conducted in deionized water,JP-10 and 4050 oil at a wide range of sliding speeds from 10 mm/s up to 2,500mm/s under the constant load 1.5 GPa/3.8 N,respectively.The studies indicated that JP-10 had decent boundary and hydrodynamic lubrication performance,but the lubricity was significantly weaker than that of professional lubricating oil.To explore tribological suface modification methods for metal-ceramic tribo-pairs lubricated by JP-10,polished M50 steel samples were treated with silver film deposition,silver film alloying,nitrogen ion implantation,TiAlN coating deposition and Ta coating alloying,respectively,and boundary tribological performance of these surface-modified and untreated M50 steel samples were studied while sliding in JP-10 against a Si₃N₄ ball in a series of high load conditions at room temperature in ambient atmosphere.It was found that surface-modified,hard samples exhibited significantly improved boundary friction and wear properties compared to original M50 steel.The present work in this dissertation reveals the interactions of PNS,PCE and JP-10 with specific surfaces in low-viscosity medium conditions and their boundary adsorption layer structural properties as well as the interactions between the layers,respectively.The research provides a reliable guidance to their molecular structure design and optimization as well as corresponding tribological surface design,and also inspires subnanometer-resolution characterization methods for boundary adsorption layers/films on tailed tribological surfaces.更多还原