Eigenspannungen,Haftfestigkeit und Verschleißeigenschaften von gesputterten,amorphen Aluminiumoxidschichten

Internal Stresses, Adhesion and Wear Behaviour of Sputtered Amorphous Alumina Coatings Thin alumina coatings have been pruduced by means of reaktive r.f. magnetron sputtering. The layers, deposited onto metallic substrates, show an amorphous crystallographic structure which may be due to the low deposition temperatures below about 250°C. Measurement of internal stresses was performed by using the bending beam method. The experiments show that there is not only a dependence on the film thickness but even pressure and sputtering power have a strong influence on internal stresses of the alumina coatings. Some correlations between internal stress and adhesion of the coatings are evident. Besides scratch-test measurements the size of layer-detachment of bending-specimen gave information about the adhesion behaviour of the coatings. The results of both methods have been in good agreement. Some of the alumina coatings have been tested with regard to their tribological behaviour by means of a model testing apparatus. The coatings show excellent wear behaviour even under severe tribological conditions.     

Impact of post-curing duration on mechanical,thermal and tribological behavior of an organic friction material

This paper aimed to study the influence of post curing duration on mechanical, thermal and tribological behavior of friction materials elaborated with simplified formulation. Surface mechanical properties and thermal conductivity were analyzed and tribological behavior was studied for various thermal severities of sliding conditions. Results indicated that post curing for long duration allowed to reduce thermal conductivity and to homogenize the surface mechanical properties of the friction material. Concerning tribological behavior, it was shown that a longer post curing duration permitted to reduce the level of friction and to increase wear resistance. Worn surface morphology investigation using SEM revealed that wear and friction mechanisms involved in the contact were sensitive to post curing duration.     

Study on the effects of nanoparticulates of SiC,Al2O3, and ZnO on the mechanical and tribological performance of epoxy-based nanocomposites

In this research work, mechanical and tribological characteristics of ortho cresol novalac epoxy (OCNE)-based nanocomposites filled with nanoparticulates of SiC, Al₂O_3, and ZnO have been investigated. Also, in these investigations, the influence of wear parameters such as applied normal load, sliding velocity, filler contents, and sliding distance have been explored. The experimental plan for four factors at three levels using face centered composite design (CCD) has been employed by the response surface methodology (RSM) technique. The friction and wear tests were carried out using a pin on disc wear test apparatus under dry sliding conditions. The hardness and flexural strength of nano ortho cresol novalac epoxy composites filled with nano (SiC, Al₂O_3, and ZnO) particulates increases with an increase in the filler contents. Whereas, the tensile strength of these nanocomposites increases with an increase in the filler contents from 1 to 2 wt%, and with a further increase in filler contents the tensile strength decreases. The results of the study also showed that (2 wt%) filler contents bring superior mechanical and tribological properties. The lowest coefficient of friction and specific wear rate were found with nano Al₂O₃-filled composites. Also, the wear mechanisms of these nanocomposites were studied using a scanning electron microscope (SEM) equipped with an EDS analyzer.     

Tribological behavior of ZA27/Al2O3/graphite hybrid nanocomposites

ZA27 alloy composites reinforced with alumina and graphite nanoparticles are a unique class of advanced engineered materials that have been developed to use in tribological applications. In this study, dry sliding wear behavior of ZA27 alloy matrix hybrid nanocomposites has been investigated. Mechanical alloying and hot pressing methods have been used for the fabrication of these composite materials. Sliding wear tests were conducted using a block-on-disc type sliding wear testing apparatus under unlubricated conditions. Scanning electron microscopy analyses have been carried out to examine the wear surfaces. The results showed that the increase of alumina nanoparticle content can positively influence improvement of the tribological behavior of the hybrid nanocomposites.     

HVOF sprayed WC–Co coatings: Microstructure,mechanical properties and friction moment prediction

This study aims at gaining a better understanding of the microstructural features that control the mechanical and the tribological performances of WC–12 wt.% Co coatings under High Velocity Oxygen Fuel (HVOF) spraying conditions. This paper looks at the influences of the HVOF process parameters for WC–12Co material on the microstructural and the tribological behaviours of the coatings. The correlation between the coating microstructure and the wear behaviour is investigated by observing and analysing the microstructure and by studying the friction moment using enhanced statistical tool based on neural computations. According to the experimental and the numerical results, it has been shown that the spray parameters affect the phase composition, hardness and porosity of HVOF sprayed WC–12Co coatings and the correlations with HVOF process parameters are fully predictable in the steady-state regime.     

Wear rate,frictional temperature,and energy consumption of steel 52100 with different microstructures during sliding

In a concerned tribological system, mechanical behavior such as friction and wear, microstructural evolution, and change in environmental temperature impact each other. A complete understanding of these interactions between the above factors is important for a tribological system to function well. In this study, the relationships among the wear rate, the frictional surface temperature, the heat consumption, and the friction energy consumption of steel 52100 with different microstructures during dry sliding were investigated using wear tests and theoretical approaches. The experimental results showed that the wear rate depends strongly on the thermal physical properties of the different microstructures due to their different energy consumptions during sliding. The calculations based on a frictional temperature field model were consistent with the experimental observations.     

Foamed-metal-reinforced composites: Tribological behavior of foamed copper filled with epoxy–matrix polymer

To improve the thermal performance and wear resistance of epoxy–matrix polymers, foamed copper materials filled with a curable epoxy matrix have been developed for tribological studies. Graphite flakes were incorporated as friction additive in the epoxy matrix. The tribological properties of foamed-copper-reinforced composites were investigated using a UMT-2 friction and wear tester. The temperature of the frictional area was measured using an infra-red thermal camera, and the effect of metallic skeletons on temperature was calculated by the finite element analysis (FEA). The results show the foamed-copper-reinforced composites are effective in transmitting heat and sharing load along the interconnected metallic skeletons, and therefore possess better thermal conductivity and wear resistance.     

The tribological properties of highly oriented cobalt and Co-Cr ion platings

Ion-plated cobalt coatings have been found to have poor tribological properties owing to the high proportion of the f.c.c. phase present. Co-Cr alloy coatings deposited by triode ion plating consist only of h.c.p. phase and have strong basal plane orientation, fine columnar structures and good tribological properties. Measurements of the tribological properties are reported and related to the coating parameters.     

超高分子量聚乙烯摩擦学性能研究进展

综述了超高分子量聚乙烯(UHMWPE)在摩擦学领域的研究进展,着重评述了UHMWPE材料在人工关节方面的应用以及在减摩耐磨材料方面的研究,并提出了UHMWPE作为减摩耐磨材料在研究与应用方面几个亟待解决的问题.     

Tribology of SiC ceramics under lubrication: Features,developments, and perspectives

Silicon carbide ceramics have many outstanding properties like high hardness, high thermal conductivity, high strength, low density, good electrical conductivity, good chemical resistance, and excellent wear resistance. Because of their valuable properties, SiC ceramics are helpful in various tribological applications. In this paper, the features and developments of tribology of SiC ceramics under lubrication are reviewed. The relevant strategies to enhance the tribological performance of SiC ceramics under lubrication, including microstructures, mechanical properties, surface characteristics, external factors, and secondary phases, are comprehensively discussed. The tribochemical reactions and Stribeck curves of SiC ceramics are also presented. Finally, future research directions of SiC ceramics in the field of tribology under lubrication are proposed. This paper aims to offer some theoretical basis for the design of low-friction and low-wear SiC ceramics under lubrication in the future and a better understanding of SiC ceramics used as various tribological components under lubrication.     

Formation mechanisms of zinc,molybdenum, sulfur and phosphorus containing reaction layers on a diamond-like carbon (DLC) coating

Diamond-like carbon (DLC) coatings are nowadays successfully applied on industrial components like pistons, piston rings and bearings in lubricated tribological contacts due to friction and wear reducing effects. In contradiction thereto, todays lubricants and additives are designed for tribological steel/steel contacts, whereby the knowledge on tribochemical layer formation on steel surfaces is comprehensive in contrast to the physical-chemical interactions between diamond-like carbon coatings, lubricants and additives. Therefore the formation mechanisms of zinc, molybdenum, sulfur and phosphorus containing reaction layers on a zirconium modified diamond-like carbon coating a-C : H : Zr (ZrC_g) in lubricated tribological contacts were analyzed by means of pin-on-disc (PoD) tribometer by varying the distances from s = 200 m–3,000 m under boundary and mixed friction conditions at T = 90 °C and a contact pressure p = 1,300 MPa regarding the application of diamond-like carbon coatings on gears. The base lubricant poly-alpha-olefin (PAO) was formulated using the anti-wear (AW) and extreme pressure (EP) additive zinc dialkyldithiophosphate (ZnDTP) and the friction modifier (FM) additive molybdenum dialkyldithiophosphate (MoDTP). The chemical composition of the tribochemical reaction layers by means of and Raman spectroscopy and x-ray photoelectron spectroscopy (XPS) as well as for the thickness differ significantly by varying the additivation.     

PS／OMMT纳米复合材料作为润滑油添加剂的摩擦学性能

用乳液聚合法制备了聚苯乙烯/有机蒙脱土(PS/OMMT)纳米复合材料,并利用 XRD对其结构进行表征.利用四球机考察了纳米复合材料在AN 10油中的摩擦学性能,表明所合成的PS/OMMT纳米杂化材料能提高基础油的抗磨性能及承载能力,降低其摩擦系数;复合材料中OMMT含量对摩擦学性能影响很大.EDX能谱研究结果表明,在低负荷下PS/OMMT纳米复合材料在钢球表面铺展成膜,在高负荷下,聚合物分解,裸露出纳米结构的高度分散蒙脱土片层具有高活性,能在钢球的磨斑表面成膜,改善润滑油高负荷下的摩擦学性能.     

Modern Solid Lubricants,Especially Based on MoS2

The structure of PVD-deposited MoS₂ films, viewed in relation to the defectfree crystalline form, present opportunities to intervene in order to improve and adapt the film properties to different tribological situations. By using modern PVD deposition technologies, it is possible to create new film structures by multilayering and co-deposition. Significant reductions in the friction coefficient, and increases in the sliding lifetime in humid atmospheres have been measured. The historical use of MoS₂ in spacecraft can be extended to industrial environments such as in dry or reduced-lubricant machining. Anti-adhesive properties are additionally important, for example in extruding and moulding.     

Influence of bias voltages on the structure and wear properties of TiSiN coating synthesized by cathodic arc plasma evaporation

Nanocomposite TiSiN films have been deposited on M2 tool steel substrates using TiSi alloy as target by a dual cathodic arc plasma deposition (CAPD) system. The influences of bias voltages on the microstructure, mechanical and tribological properties of the films were investigated. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction techniques were employed to analyse the microstructure, grain size and residual stress. Nano-indentation and tribometer testers were used to measure the mechanical and tribological properties of nanocomposite TiSiN thin films. The results showed that the hardness of the films ranged from 25 to 37 GPa, which were higher than that of TiN (21 GPa). The coefficient of friction of the TiSiN thin films was more stable but was higher than that of TiN when wear against both Cr steel and WC-Co ball, respectively. When encountered with both Cr steel and WC-Co ball of the counter ball, the tribological mechanisms of TiSiN thin films are adhesive and abrasion wears, respectively. It has been found that the microstructure, mechanical and wear properties of the films were correlated to bias voltage, grain size, and amorphous Si₃N₄ nanocomposite formed in film structure, resulting in a superhard TiSiN coating.     

PTFE及纳米粒子改性环氧树脂基聚酯织物增强复合材料的拉伸及摩擦学性能

为了研究填料(纳米粒子和PTFE)对聚酯织物增强复合材料的拉伸及摩擦学性能(轴向及偏轴方向)的影响,使用手糊成型的方法制备了四种环氧树脂基聚酯织物增强复合材料.根据拉伸应力-应变曲线和断口形貌图讨论了拉伸断裂机理.使用环-块式结构的Amsler摩擦磨损试验机测试织物增强复合材料的摩擦学性能.结果表明:对于纯环氧树脂/织物增强复合材料来说,聚酯织物在整个织物增强复合材料的拉伸和摩擦磨损测试中起到了主要的抗拉和耐磨作用;但当在环氧树脂中加入填料后,环氧树脂基体在抗拉和耐磨性方面起到了越来越重要的作用.拉伸性能的提高是由于纤维-基体间界面的改善;由于填料具有优异的摩擦磨损性能,从而使织物增强复合材料的摩擦学性能得到了提高;并且纳米粒子和PTFE对于织物复合材料性能的提高起到了协同的作用.织物增强复合材料偏轴方向的拉伸性能和摩擦学性能与其在轴向的拉伸性能和摩擦学性能不同.     

Tribological property enhancement of CrN films by metal vapor vacuum arc implantation of Vanadium and Carbon ions

CrN films have been extensively used in precision forming and molding applications because of their excellent tribological properties and oxidation-resisting characteristics. Vanadium and carbon ions are introduced into the near surface layer of deposited CrN films via metal vapor vacuum arc implantation to improve the wear performance of CrN films. Dense and smooth CrN film was deposited using a filtered arc deposition system, which provides fully ionized Cr plasma on the substrate surface. Subsequently, surface bombardment of the deposited CrN film with vanadium and carbon ions densifies the film and forms an alloy near the surface. These CrN-based films were characterized by X-ray photoelectron electron and Auger electron spectroscopies. Examinations of the tribological and mechanical film properties, including wear resistance, corrosion resistance and fracture toughness were performed and correlated with respect to the implantation parameters.     

制动用C/C-SiC复合材料摩擦学性能研究现状

C/C-SiC复合材料是高速制动材料的优良候选材料。摩擦磨损性能是衡量制动材料的主要性能指标,也是制约材料进一步应用的主要因素。主要从材料微观结构和成分以及工况条件对C/C-SiC复合材料的摩擦磨损性能的影响两方面阐述了C/C-SiC复合材料摩擦磨损性能的研究现状;分析了影响C/C-SiC复合材料摩擦磨损性能的主要材料因素和工况条件;讨论了各自影响机制;并提出了进一步提高C/C-SiC复合材料摩擦磨损性能和使役安全所需解决的问题。     

Comparative Study of Turning of 4340 Hardened Steel with Hybrid Textured Self-Lubricating Cutting Inserts

The tribological properties of mating surfaces have been altered extensively using surface texturing. In the present paper, hybrid textures have been developed using the Nd:YAG laser on carbide inserts. The experimental investigations have been performed to study the effect of different textured cutting inserts while machining 4340 hardened steel. CaF₂ has been used as a solid lubricant to make the cutting inserts self-lubricating in nature. The comparative analysis showed that the cutting forces, roughness of the machined workpiece, and chip thickness ratio get significantly reduced by using the so-developed cutting inserts. SEM images of the chips formed during the cutting process have been analyzed to find a less chip saw tooth phenomenon by using hybrid textured cutting inserts.     

Selection of ceramics for methanol fuel injector plungers based on tribological characteristics when coupled with 4140 steel

This research seeks to increase the working life of methanol fuel injectors by substituting wear- and corrosion-resistant ceramics for the current materials of construction. Because information on the tribological properties of ceramics in methanol is scarce, experiments were performed to characterize the dynamic friction and wear behavior of 11 oxides, nitrides and carbides against nitrided 4140 steel using a reciprocating test machine. The results are compared to baseline tests performed with typical injector construction materials (nitrided 51501 steel and nitrided 4140 steel) that have experienced early wear using methanol fuel. The tribological performance was characterized through measurements of the friction coefficient, mass loss, gross dimensional change and the roughness of the wear scar and by examinations with a scanning electron microscope. All of the ceramics were wear resistant, but many caused severe wear on the 4140 steel. A boron carbide and a nickel-bonded titanium carbide exhibited the best tribological characteristics.     

Effects of Yttria Addition on Microstructure,Mechanical Properties,Wear Resistance and Corrosive Wear Resistance of TiNi Alloy

TiNi alloy has a high resistance to wear and could be an excellent candidate for various tribological applications. But studies show that oxygen active elements can improve properties of some alloys,markedly.Yttrium is one of the oxygen active elements.In this paper,the e-ects of yttria addition on properties of TiNi have been studied via micro-indentation,hardness,wear and corrosive wear tests.It is demonstrated that by addition of yttria to 5%,TiNi alloy can own improved mechanical properties and resistan...