A brief review on the wear mechanisms and interfaces of carbon based materials

Abstract

The demand for reducing wear and friction has become the chief aim in the automotive industry nowadays. The usage of lubricant is not considered enough as there is still room for improvements. As a solution, much research has arisen towards what we called self-lubricating ideas, in order to reduce friction better than lubricant. This paper presents an overview wear mechanism and the interface of carbon-based materials. This paper will also discuss the interfaces by carbon as substrate and coating layer. The findings show that for metals, the predominant wear mechanisms were abrasion and fatigue. Meanwhile, for polymers and coating (DLC), they were abrasive along with adhesive wear. The surface roughness of the substrate plays a crucial role in increasing the excellent performance of the DLC coating. The interfaces of carbon elements definitely give huge impact on both self-lubricant materials and coatings where the coefficient of friction and wear rate changes drastically even with 1 wt.% addition. Nevertheless, a clear understanding of the factors that affect the tribological performance is very essential in performance improvement for potential applications.     

Subsurface deformation studies of aluminium during wear and its theoretical understanding using molecular dynamics

Adopting the bonded interface technique for wear experiments under vacuum, this paper reports the nature of the localised shear bands that appear at the different deformation zones of the subsurface of aluminium under different sliding conditions. The plastic deformations are mapped under both low load/low sliding velocities as well as high load and high sliding velocities. A monotonic change in local plastic strain as a function of depth at low sliding velocities give way to a discontinuity separating two different zones with differing plastic behaviour for high sliding speed wear test. Besides shear bands, bonded interface also reveals the presence of kinks particularly in the samples subjected to wear test with high sliding velocities. A molecular dynamic simulation of the wear process successfully replicated the experimental observation, thus allowing us to discuss the mechanism of subsurface deformation during the wear process in the absence of any significant oxide layer for aluminium under sliding condition.     

火焰喷涂重熔Ni基WC复合涂层的耐磨性能试验研究

利用火焰喷涂重熔方法制备了Ni基WC复合涂层，并进行了耐磨性能试验研究.通过扫描电子显微镜观察涂层磨损后的表面形貌，分析了WC体积分数、颗粒分布均匀性、包裹粉颗粒尺寸对涂层耐磨性的影响.结果表明:涂层硬度和耐磨性随着WC体积分数增加而提高，当WC体积分数过高时，降低了涂层致密性，其硬度和耐磨性反而有所下降；聚乙二醇(PEG)400+PEG2000+无水乙醇混粉方式的WC颗粒分布最均匀，降低了涂层磨损量；加入相同体积分数的亚微米级WC所制备的涂层耐磨性较微米级WC所制备的涂层耐磨性好. 关键词： 火焰喷涂 显微组织 颗粒尺寸 耐磨性能     

Carbon-Fiber-Reinforced Plastics Based on an Imide Polymerizing Oligomer Binder with a Semi-Interpenetrating Structure

Semi-interpenetrating polymer networks (SIPNs) are synthesized based on a polyimide binder (imide polymerizing oligomer) with addition of polyamide acid. As acylating agents, they include derivatives of benzophenone-tetracarboxylic and diphenyloxide-tetracarboxylic acids and as aminocomponents - diaminodiphenylmethane, diaminodiphenyloxide, and metaphenylene diamine. It is shown that these systems form SIPNs of the snake-in-the-cage type. Uncured compositions forming melts at 300-330°C are used as binders for carbon-fiber-reinforced plastics (CFRP). The homophase structure of the SIPNs in CFRP is shown by dynamic mechanical tests. The interlaminar fracture toughness (G _1c) is measured by the method of a double cantilever beam. It is found that G _1c, as a function of the content (wt.%) of polyamid acid (PAA) in the initial composition used for obtaining CFRP, is of linear character, which is another confirmation of the homophase structure of the SIPNs. The interlaminar fracture toughness achieved for CFRP is 340 J/m² at a 30% PAA content in the initial composition, and the glass transition temperature, which determines the thermal stability of the composites, reaches 320°C. The prospects of employing these plastics in tribotechnics are discussed.     

脉冲高能量密度等离子体法制备TiN薄膜及其摩擦磨损性能研究

利用脉冲高能量密度等离子体技术在室温条件下在45号钢基材上制备出了超硬耐磨TiN薄膜.利用XRD，XPS，AES，SEM等手段分析了薄膜的成分及显微组织结构，并测试了薄膜的硬度分布及摩擦磨损性能.结果表明：薄膜主要组成相为TiN，薄膜组织致密、均匀，与基材之间存在较宽的混合界面；薄膜硬度高，在干滑动磨损实验条件下具有优异的耐磨性及较低的摩擦系数. 关键词： 脉冲高能量密度等离子体 TiN膜 显微组织 耐磨性     

Proton irradiation effects on the structural and tribological properties of polytetrafluoroethylene

Polytetrafluoroethylene (PTFE) was irradiated with protons in a ground-based simulation facility to study the effects of proton irradiation on the structural and tribological properties of PTFE. The structural changes were characterized by X-ray photoelectron spectroscopy (XPS) and attenuated total-reflection FTIR (ATR-FTIR), while the tribological properties were evaluated by friction and wear tests. It was found that proton irradiation induced the degradation of PTFE molecular chains, resulting in the increase of C concentration and the decrease in F concentration on the sample surfaces, and the surface chemical structure and morphology of the samples changed, which affected the friction coefficient and decreased the wear rate of the specimens as the friction and wear tests revealed.     

Tribological behavior of Al-based self-lubricating composites

Abstract

Aluminum-based composites containing either SiC (Al10%SiC) as the hard phase or a combination of SiC and MoS₂ (Al10%SiC4%MoS₂) have been synthesized following stir casting route. To overcome the poor wetting characteristics, magnesium was added in one of the composites (Al10%SiC4%MoS₂4%Mg) to improve the bonding between matrix and second phase. The results suggested an enhancement in hardness and strength of the composite containing SiC–MoS₂ and Mg, thus indicating the effectiveness of Mg addition in improving the interfacial bonding strength. Tribological performance of the composites has been examined by carrying out pin-on-disk wear tests under dry sliding conditions at different normal loads of 9.8, 14.7, 19.6, and 24.5 N and at a constant sliding speed of 1 m/s. Both the friction coefficient and the wear rate have been found to reduce with addition of MoS₂; however, bonding between the matrix and reinforcements was not good. Al10%SiC4%MoS₂4%Mg has shown the best tribological performance at all the loads in terms of the lowest friction coefficient and the lowest wear rate. The wear mechanism has been found to be a combination of adhesion and abrasion as indicated by the presence of some abrasive grooves and delaminated flakes at the worn surface and the X-ray examination of wear debris for all the materials used in the present investigation.     

Synthesis and tribological properties of AA5052-base insitu composites

Abstract

It is important to optimize the properties of a material for a particular application, hence, to find the suitable material for tribological applications, the wear and friction behaviour of AA5052 in situ composites with different kind of reinforcements have been investigated. For present study, three in situ formed composites have been produced with different reinforcements namely Al₃Zr, ZrB₂ and combination of both (Al₃Zr + ZrB₂) by direct melt reaction (DMR) technique. The as-cast composites and base alloy have been characterized by X-ray diffraction (XRD), optical microscopy, electron microscopy, tensile testing, hardness and dry sliding wear and friction tests. XRD results indicate the successful formation of second phase reinforcement particles in all composites. Wear test results indicate that the cumulative volume loss increases with an increase in sliding distance while coefficient of friction shows a fluctuating tendency, whereas with increasing applied load, wear rate shows an increasing trend while coefficient of friction shows decreasing trend. The variation of wear rate with composites indicates that the composite with multiple reinforcement (Al₃Zr + ZrB₂) has lowest wear rate among all as-cast composites and base alloy, while coefficient of friction is higher. The responsible mechanisms concerned with wear and friction results have been discussed in detail with the help of the observation on worn surface analysis by scanning electron microscope (SEM) and 3D-profilometer. All tribological results have been correlated with the microstructural properties, strength parameters and bulk hardness of the composites.     

Indentation behaviour of superelastic hard carbon

Superelastic hard carbon particles widely varying in structure and properties have been studied by instrumented microindentation technique. The carbon particles up to 200 μm in size were produced by fullerene collapse upon high-pressure high-temperature treatment of metal–fullerene powder mixture with simultaneous sintering of metal matrix composite materials (CM) reinforced by the particles. The structure and properties of the carbon particles were controlled by changing synthesis parameters and the state (composition and structure) of the parent fullerite crystals. The specific features of the instrumented indentation behaviour of the particles were studied as a function of their hardness. Mechanical properties of the particles tested at loads of up to 1970 mN exhibit an indentation size effect, which becomes more pronounced with increasing hardness of the carbon particles. Upon holding at a constant load, the fullerene-derived carbon particles undergo unrecoverable deformation, and the indentation creep C_IT increases with increasing particle hardness. An increase in hardness of the reinforcing carbon particles substantially improves the wear resistance of the CM and decreases their friction coefficient.     

Plasma-induced deposition of titanium nitride from TiCl4 in a direct current glow discharge: Control of the chlorine content and gas-phase nucleation

Titanium nitride thin films have been deposited from TiCl₄, N₂, and H₂, in a low-pressure glow discharge at temperatures of 500°C, which are compatible with most applications. Based on our earlier work on the effect of tire plasma parameters on the chemical pseudoequilibrium in this and in similar systems, the chlorine content could he reduced to less than 2 at %. Suppression of the positive column reduced the gas-phase reaction within the reactor volume and the concomitant homogenous nucleation Dense, vent hard films with golden color could he deposited on various substrates including silicon and steel.