Tribological properties of grey cast iron lubricated using organic compounds containing Mo and ZnDTP additives

The lubricating effectiveness of organic compounds containing Mo and ZnDTP in different ratios in poly‐alpha‐olefin (PAO) was investigated using an Optimol SRV‐IV (Optimol Instruments, Munich, Germany) reciprocating friction and wear tester. The morphologies of the worn surfaces were observed using a scanning electron microscope with energy‐dispersive X‐ray spectroscopy. The chemical states of several typical elements on the worn surfaces of grey cast iron discs were examined by means of X‐ray photoelectron spectroscopy (XPS). The results indicated that the grey cast iron discs exhibited different friction‐reducing and wear‐resistance capabilities when lubricated with PAO containing MoDTP and ZnDTP additives in different ratios. The lowest frication coefficient is only 0.072. XPS analyses indicated that ZnDTP + MoDTP and ZnDTP + MoDTC formed different chemical products. Copyright © 2012 John Wiley & Sons, Ltd.     

在高温条件下陶瓷涂层润滑性能的试验研究

在optimo SRV高温摩擦磨损试验机上对金陶瓷涂层Cr_3 C_2/NiCr/Mo的润滑性能进行了试验研究。试验是在边界润滑条件下进行的,温度范围为50℃～850℃。使用的润滑剂为双酯油,添加ZnDTP添加剂。在扫描电子显微镜,波谱分析仪和X光电子能谱仪XPS上对磨损后的表面进行了观察和分析。表明Mo对在不同温度下形成各种润滑物质起重要作用。这些物质有吸附膜、ZnS.、MoS_2、石墨和MoO_3等,它们在一定程度上保护了摩擦表面。     

Investigation of antiwear coatings deposited by the pvd process

The tribological properties of various PVD‐deposited coatings (vacuum arc method) have been tested, both single‐layer coatings (TiN, CrN, Ti(C,N), and Cr(C,N)) and multilayer coatings (Cr(C,N)/CrN/Cr and CR(C,N)/(CrN+Cr₂N)/CrN/Cr). An unlubricated ball‐on‐disc tribosystem was used in which an Al₂O₃ ball is pressed against a coated steel disc rotating in the horizontal plane. A novelty of the method is the removal of wear debris from the contact zone using a draught of dry argon. This improves the repeatability of the test results and the stability of the tribological characteristics. It is shown that CrN coatings exhibit the best antiwear properties and Ti(C,N) the worst. Multilayer coatings have better antiwear properties than single‐layer ones. The friction coefficients for CrN and Cr(C,N) coatings are much smaller than for the commonly used TiN. A correlation has also been found between the physical properties of the coatings tested (adhesion of the coating to the substrate assessed in scratch tests, and coating hardness) and their antiwear properties. An improvement in coating‐substrate adhesion results in wear reduction, while greater hardness (causing a coating embrittlement increase and a change in the wear mechanism) brings about greater wear. There is no correlation between the physical properties and the friction coefficients of the coatings tested.     

Tribological behaviour and wear mechanism of MoS2–Cr coatings sliding against various counterbody

MoS₂–Cr coatings with different Cr contents have been deposited on high speed steel substrates by closed field unbalanced magnetron (CFUBM) sputtering. The tribological properties of the coatings have been tested against different counterbodies under dry conditions using an oscillating friction and wear tester. The coating microstructures, mechanical properties and wear resistance vary according to the Cr metal-content. MoS₂ tribological properties are improved with a Cr metal dopant in the MoS₂ matrix. The optimum Cr content varies with different counterbodies. Showing especially good tribological properties were MoS₂–Cr8% coating sliding against either AISI 1045 steel or AA 6061 aluminum alloy, and MoS₂–Cr5% coating sliding against bronze. Enhanced tribological behavior included low wear depth on coating, low wear width on counterbody, low friction coefficients and long durability.     

Friction Reduction and Antiwear Capacity of Engine Oil Blends Containing Zinc Dialkyl Dithiophosphate and Molybdenum-Complex Additives

The efficacy of oil blends containing zinc dialkyl dithiophosphate (ZnDTP) and molybdenum (Mo)-complex additives to improve the tribological properties of boundary-lubricated steel surfaces was investigated experimentally. The performance of oil blends containing three different types of Mo-complex additives of varying Mo and S contents with or without primary/secondary ZnDTP additions were investigated at 100°C. The formation of antiwear tribofilms was detected in situ by observing the friction force and contact voltage responses. Wear volume and surface topography measurements obtained from surface profilometry and scanning electron microscopy studies were used to quantify the antiwear capacity of the formed tribofilms. The tribological properties are interpreted in terms of the tribofilm chemical composition studied by X-ray photoelectron spectroscopy. The results demonstrate that blending the base oil only with the Mo-compound additives did not improve the friction characteristics. However, an optimum mixture of Mo complexes and ZnDTP additive provided sufficient amounts of S and Mo for the formation of antiwear tribofilms containing low-shear strength MoS ₂ that reduces sliding friction. In addition, the formation of a glassy phosphate phase due to the synergistic effect of the ZnDTP additive enhances the wear resistance of the tribofilm. This study shows that ZnDTP- and Mo-containing additives incorporated in oil blends at optimum proportions improve significantly the tribological properties of boundary-lubricated steel surfaces sliding at elevated temperatures.     

甘油润滑下CrCN涂层的超低摩擦特性

为开发与CrCN涂层具有良好配伍润滑性能的绿色润滑剂,使用磁控溅射技术在304不锈钢表面沉积CrCN涂层,利用场发射扫描电子显微镜、原子力显微镜、纳米压痕仪、维氏硬度计、X射线衍射仪、X射线光电子能谱仪分别对其表面形貌、涂层厚度、力学性能、物相组成以及元素化学价态进行分析,并借助多功能摩擦磨损试验机评价在甘油润滑下CrCN涂层的摩擦学性能,并与PAO6润滑下结果进行比较。利用磁控溅射技术在不锈钢表面构筑的CrCN涂层表面光滑致密,粗糙度仅为1.01 nm,硬度可达14.39 GPa。对比钢-钢和钢-CrCN体系的摩擦学性能发现,钢-CrCN体系在甘油润滑下展现出优异的润滑性能;当负载为0.5 N时,钢-CrCN体系在甘油润滑下的摩擦因数可低至0.01,大大低于PAO6润滑下的摩擦因数。对磨痕的XPS分析表明,在摩擦过程中,甘油发生摩擦化学反应,在CrCN涂层的接触表面生成一层FeOOH层,甘油分子及其降解产物可能进一步吸附在FeOOH层,形成流体润滑层,有效降低了摩擦和磨损。     

多元CrMoSiCN系列薄膜结构及摩擦学特性研究进展

从三元含Mo的Cr-Mo-N、Mo-Si-N、Mo-C-N薄膜到四元Cr-Mo-Si-N、Mo-Si-C-N薄膜,综述多元系列薄膜的结构、力学及摩擦学性能的研究进展;分析在不同气体压力、制备方法与参数、不同元素含量下薄膜结构的变化,阐述薄膜结构与其力学性能和摩擦学特性的关联。指出:多元Cr-Mo-Si-C-N系列薄膜结构、硬度、摩擦因数强烈受到薄膜中Mo、Si、C、N元素含量的影响,其中力学特性还与薄膜微结构紧密相关;薄膜的摩擦学特性与晶粒生长细化和作为润滑剂的无定形基质有关;在摩擦过程中发生的摩擦化学反应也有效地提高了薄膜的耐磨性。对于四元Cr-Mo-C-N和多元Cr-Mo-Si-C-N薄膜,建议进一步研究在水润滑与非润滑的不同条件下,例如在海水或者空气干摩擦环境下,是否由于薄膜结构组分的不同而有效地形成含Mo的氧化物的自润滑膜,以提高薄膜在更多场合下的适应性和减摩性。     

The tribological performance of DLC-based coating under the solid–liquid lubrication system with sand-dust particles

Combination of solid and liquid lubricants to meet emission or environmental requirements of future tribological systems while providing the levels of desired friction and wear performance have received considerable research attention in the near term. The aim of the present work was to investigate the tribological behavior of oil-lubricated (PAO, PFPE, SO, IL and MAC) DLC coated surfaces under the conditions without and with sand-dust particles. The effects of applied load, frequency, and sand-dust particles on the tribological performance of DLC coating were systemically studied. The analysis results showed that solid–liquid lubricating coatings including SO and IL exhibited excellent anti-friction (～0.026) but relative poor wear-resistance performances under the conditions without and with sand-dust environments. But for PFPE and PAO, they demonstrated the worst tribological behaviors with high friction coefficient and wear rates. The added sand-dust particles lead to the wear rates to the one order of magnitude large than that without sand-dust conditions for all the selected liquid lubricants. The viscosity, contact angle and work of adhesion played an important part in affecting the tribological performances. The lubrication regimes in Stribeck curve for the five kinds of liquid lubricants were affected obviously by the sand-dust particles in different way. The formed transfer films on the coating surface and pin have much influence on the tribological behavior and the transition between lubrication regimes.     

花状与球状MoS2对PAO15润滑油摩擦学性能的影响

为改善低黏度PAO15润滑油的摩擦学性能,通过水热法制备球形与花状MoS_2颗粒,采用X射线衍射仪(XRD)与扫描电子显微镜(SEM)对所制备的MoS_2颗粒进行表征。制备球形与花状MoS_2改性的PAO15油,利用四球摩擦试验机对比研究2种形貌MoS_2在不同用量条件下对PAO15油摩擦学性能的影响。采用光学显微镜、表面轮廓仪、扫描电子显微镜(SEM)与能谱仪(EDS)对磨痕表面进行表征。结果表明:制备的球形与花状MoS_2晶型均较好地符合MoS_2的晶型,掺杂至PAO15油中均能够提升其摩擦学性能,使其摩擦因数降低;随着MoS_2颗粒添加量的增加,PAO15油摩擦学性能有所提升,在质量分数为1.0%时达到最优;花状MoS_2具有更大的比表面积,其对PAO15油抗磨损性能的提升优于球形MoS_2,形成的转移膜能够更好地起到隔离摩擦表面的作用。     

电弧喷涂7Cr13涂层的组织结构及摩擦学机理

研究了φ2mm粉芯丝材电弧喷涂7Cr13涂层的摩擦学性能，并借助X光电子能谱，X射线衍射分析，扫描电子显微镜等表面分析技术研究了其作用机理，结果表明，电弧喷涂7Cr13涂层具有较优的抗磨减摩性能，其磨损机制主要是磨料磨损和分层磨损，与GCr15试环对摩时，试环表面形成了主要含Cr2O3的转移膜。     

Tribological Behaviors of Different Diamond-Like Carbon Coatings on Nitrided Mild Steel Lubricated With Benzotriazole-Containing Borate Esters

Three synthesized benzotriazole-containing borate esters were separately added into poly-alpha-olefin (PAO) as additives, using molybdenum dithiocarbamate (MoDTC) as the comparison. The friction and wear behavior of Ti-DLC and Ti/Al-DLC coating on nitrided AISI-1045 steel sliding against AISI 52100 steel under the lubrication of PAO containing various additives was evaluated using a reciprocating ball-on-disk friction and wear tester. The morphology and chemical feature of the worn surfaces of the DLC coatings were observed and analyzed using a three dimensional (3D) surface profiler, a scanning electron microscope (SEM), and an X-ray photoelectron spectroscope (XPS). Results show that the three kinds of benzotriazole-containing borate esters as additives in PAO had much better tribological properties than MoDTC; the wear resistance of Ti/Al-DLC coating was better than Ti-DLC coating.     

润滑添加剂对金属带式无级变速器油摩擦学性能的影响

采用MMW-1P摩擦试验机和振子油性摩擦试验机评定了添加剂含硫化合物、磷酸酯、油酸异辛酯、锌盐、钼盐和硼盐在加氢油150N和聚α-烯烃PAO6中的摩擦和磨损性能。结果表明在低滑动速度下仅磷酸酯和锌盐的摩擦因数随滑动速度的增加而增大;在相同的低滑动速度下磷酸酯和锌盐的摩擦因数稳定,且平均摩擦因数值较大,并具有较好的抗磨性能,适宜作为以加氢油或聚α-烯烃为基础油的金属带式无级变速器的润滑添加剂。     

镍基合金喷熔层摩擦学行为与机制的研究

采用热喷熔工艺制备了两种镍基合金喷熔层,并选用高锰钢、不锈钢作为对比材料,研究了镍基合金喷熔层的摩擦磨损性能。研究结果表明：镍基合金喷熔层具有良好的耐磨损性能和较低的摩擦系数。镍含量对喷熔层的摩擦学性能有显著影响,高镍含量的镍基合金,其耐磨性能明显优于低镍含量的镍基合金。在低速轻载条件下,镍基合金喷熔层的磨损机理为微观犁削;高速重载时,表现为粘着磨损和磨料磨损,其中高镍含量的喷熔层表面形成了致密的转移膜,有效地降低了磨损率。     

Comparative study of the tribological properties of ionic liquids as additives of the attapulgite and bentone greases

Three kinds of ionic liquids (1‐butyl‐3‐methylimidazolium hexafluorophosphate (L‐P104), 1‐hexyl‐3‐methyl imidazolium hexafluorophosphate (L‐P106) and 1‐octyl‐3‐methylimidazolium tetrafluoroborate (LB108)) were added to the attapulgite base grease and the bentone base grease to investigate and compare the tribological behaviours of the ionic liquids with the two base greases at room temperature and 150°C. Tribological tests were performed using a ball‐on‐plate reciprocating tribometer. The attapulgite base grease showed better wear resistance properties than that of bentone base grease by adding ionic liquids as additives. At same time, the attapulgite base grease showed excellent friction‐reducing and wear resistance properties at high temperature (150°C). Also, we discussed the tribological mechanism of the attapulgite base grease at both room temperature and 150°C from the aspect of the structure of the grease thicker. Copyright © 2012 John Wiley & Sons, Ltd.     

Friction reduction by metal sulfides in boundary lubrication studied by XPS and XANES analyses

In this work, the antiwear action of zinc dithiophosphate (ZnDTP) in combination with friction modifier agent molybdenum dithiocarbamate (MoDTC) has been investigated. A Cameron-Plint friction machine was used to generate large tribofilm areas in mild tribological conditions. Two analytical techniques, X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) spectroscopy, have been employed to characterize the chemical species in tribofilms. XANES spectroscopy at the P K and L-edge, Mo L and M-edge and S K-edge was carried out in order to investigate phosphates and sulfides species in the tribofilms This was followed by XPS analysis in the same location in the tribofilms. Special attention has been paid to the peak fitting of Fe 2p, Zn 2p, S 2p, Mo 3d and O 1s photopeaks and Auger ZnLMM lines. The combined analyses have shown that the MoDTC+ZnDTP containing oil produces mainly shorter chain metal polyphosphate material in addition to ZnS and MoS₂. No zinc sulfate has been detected. XPS confirms that the formation of MoS₂ is enhanced by the presence of ZnDTP. For all additives combinations; no iron has been detected in the tribofilms. Analytical results are discussed and compared with theoretical predictions from the Chemical Hardness model for ZnDTP, MoDTC and ZnDTP+MoDTC tribofilms formation.     

Tribological behaviour of protic ionic liquids with ammonium salts modified LABSA as lubricants and additives

Two typical protic ionic liquids with ammonium salts modified linear alkylbenzene sulfonic acid (LABSA) were synthesised, and their tribological behaviours used as both lubricants compared with PAO10 and additives in PAO10 were evaluated with an Optimol SRV‐I oscillating reciprocating friction and wear tester. The results show that the two novel protic ionic liquids with ammonium salts modified LABSA exhibited excellent friction‐reducing and anti‐wear properties as lubricants and can also significantly improve the tribological performance of the base fluids as friction modifier additives. The worn surfaces were characterised by scanning electron microscope and X‐ray photoelectron spectroscopy, indicating that the excellent anti‐wear and friction‐reducing performance could attributed to the boundary lubrication films that could contain both the tribochemical film composed of organic amine decomposed from the protic ionic liquids with ammonium salts and the stable chemical absorbed film through the interactions between the sulfonate anions and surface metallic atoms during the sliding process. Copyright © 2012 John Wiley & Sons, Ltd.     

几种金属纳米粒子作润滑脂添加剂的试验研究

用Falex四球摩擦磨损试验机考察了镍、钴、铬、钼、铁-钴及铁-镍合金纳米粒子作为添加剂加入润滑脂的摩擦学行为。结果表明：添加纳米粒子的润滑剂均具有较好的减摩抗磨性能和较高的承载能力(PB值)，合金纳米粒子比金属单体纳米粒子的添加效果好，纳米粒子质量分数在3％左右时润滑脂具有较佳的摩擦学性能。     

磷酸锰转化涂层和硫化亚铁涂层的摩擦学性能对比

为了在重载蜗杆传动中以钢蜗轮替代青铜蜗轮,在20Cr钢表面分别制备了超微细磷酸锰转化涂层和硫化亚铁涂层,在摩擦磨损试验机上对两种涂层的摩擦学性能进行了对比;用SEM和EDX分析了涂层表面、磨损面的形貌与成分,采用XRD分析了涂层的相结构。结果表明:在载荷低于300 N时,两种涂层均具有良好的减摩耐磨性能;当载荷大于500 N时,硫化亚铁涂层的减摩耐磨效果不明显,而超微细磷酸锰转化涂层具有持续的减摩耐磨特性。     

Friction‐induced two‐dimensional solid films from lubricant additives

Tribochemical interactions between some lubricant additives, namely zinc dithiophosphate (ZnDTP), an antiwear additive, molybdenum dithiocarbamate (MoDTC), a friction modifier, and overbased calcium borate (OCaB) detergent, have been investigated. The nature of the tribofilms formed was studied by combining high‐resolution transmission electron microscopy of wear fragments and inside wear scars with micro‐spot X‐ray photoelectron spectroscopy at the same location of the wear track (‘dual’ analysis). The OCaB/ZnDTP/MoDTC ternary system provides both a low wear rate and ultralow friction, while adding detergent and anti‐corrosion properties to the formulation. The analytical data indicate that such a synergistic effect can be attributed to an outstanding feature of the tribofilm nanostructure: it is composed of perfectly oriented MoS₂ single sheets embedded in a single‐phase calcium and zinc borophosphate glass. Compared to phosphate alone, MoS₂ sheets are oriented by the borophosphate phase. This could be related to a template effect of friction‐aligned planar molecules of the glassy borate polymer.     

Sliding contacts for the pharmaceutical industry: failure analysis and dry sliding tests for the replacement of hard Cr on AISI 316L steel

Several alternatives were compared for the replacement of hard electroplated Cr coating to improve the tribological properties of the AISI 316L austenitic stainless steel for pharmaceutical packaging applications, including low temperature carburizing (LTC), thermal spray coatings (Al₂O₃-13TiO₂, WC-17Co), substitution of the AISI 301 reference counterface with polymeric materials (PTFE, UHMWPE, PEEK). In dry sliding block on ring tests, the LTC AISI 316L cylinders lead to the lowest wear rates of the AISI301 sliders under low loads (up to 10 N). When considering the polymer vs. uncoated AISI 316L couple, PEEK and UHMWPE lead to lower friction and comparable wear rates with respect to the reference couple (AISI 301 vs. Hard Cr coated-AISI 316L) in the whole range of tested loads.