Fe基非晶涂层的组织结构与耐磨性研究

利用电弧喷涂技术在45#钢基体上制备了Fe基非晶合金涂层。与YG8球配副,在干摩擦条件下对涂层与45#钢的摩擦磨损性能进行了对比研究。采用XRD、扫描电镜及显微硬度计等分析仪器对涂层组织结构及磨损形貌进行表征。结果表明:涂层中含有非晶相,孔隙率较少,涂层平均硬度高达HV1124。与45#钢相比,涂层的摩擦因数较小,耐磨性明显高于45#钢基体,其磨损机制以片状剥落为主。     

Microstructure and Wear Behaviors of Plasma-Sprayed FeCrNiMoCBSi Coating with Nano-Grain Dispersed Amorphous Phase in Reciprocating Sliding Contact

A novel FeCrNiMoCBSi amorphous/nanocrystalline coating was fabricated using a plasma spraying process. The coating was dense with a low porosity of approximately 0.99%. The coating consisted of a 67.8 vol% amorphous phase coupled with many nanocrystalline grains that were approximately 5?nm in diameter. The mechanical properties of the as-sprayed coating were determined by nanoindentation measurement, and the tribological behaviors were systematically investigated in a reciprocating sliding contact. The results show that FeCrNiMoCBSi coatings possess superior wear resistance compared to other typically similar Fe-based amorphous coatings. The tribological behaviors evolve with the combination of normal load and sliding velocity. Herein, the dominant wear mechanisms are delamination wear and oxidation wear. With an increase in normal load and sliding velocity, the abrasive wear is gradually weakened, the formation of oxide films on the worn surfaces is facilitated, and wear debris is ground to powder. The oxide films suffer from fatigue wear with induced cracks undergoing reciprocating sliding effects.     

Friction and Wear Characteristics of C/Si Bi-layer Coatings Deposited on Silicon Substrate by DC Magnetron Sputtering

The tribological behavior of carbon/silicon bi-layer coatings deposited on a silicon substrate by DC magnetron sputtering was assessed and compared to that of amorphous carbon and silicon coatings. The motivation was to develop a wear resistant coating for silicon using thin layers of amorphous carbon and silicon. Wear tests were conducted by sliding a stainless steel ball against the coating specimens under applied normal loads in the range of 20?~?50?mN. Results showed that the wear rate of the bi-layer coating was strongly dependent on the ratio of thickness between the carbon and silicon layers. The wear rate of the bi-layer coating with 25?nm thick carbon and 102?nm thick silicon layers was about 48 and 20 times lower than that of the single-layer amorphous carbon and amorphous silicon coating, respectively. In addition, the steady-state friction coefficient of the bi-layer coating could be decreased to 0.09 by optimizing the thickness of the layer. Finally, a model for the wear reduction mechanism of the carbon/silicon bi-layer coating was proposed.     

Effects of sliding velocity and applied load on the tribological mechanism of amorphous poly-ether–ether–ketone (PEEK)

In this work, the effects of sliding velocity and applied load on the tribological characteristics, i.e. friction coefficient and wear rate, of an amorphous poly-ether–ether–ketone (PEEK) coating was examined. Friction tests were performed on a ball-on-disc apparatus. Based on analyses of the worn tracks, a comprehensive attempt is made to approach the tribological mechanism of amorphous PEEK. A hypothesis is proposed that the tribological behaviour of the amorphous PEEK is closely related to its viscoelastic behaviour. The sliding velocity plays significant roles on the tribological characteristics by influencing the interface temperature and strain rate of the PEEK surface layer involved in the friction process. The applied load influences the tribological performance by varying the strain range in the surface layer.     

Nanostructured carbon coating-orientant and its interaction with boundary lubricating layers

In previous works we have shown that to improve oil lubricity one should increase the orientability of the working surfaces of solid bodies. This can be achieved by applying special carbon orientant coatings to ensure the formation of highly oriented boundary layers whose molecules acquire some orientation under the effect of the solid-phase force field. The level of the orientation effect and coating characteristics are dependent on its synthesis parameters, which makes it possible to regulate them during coating application. It is shown that with increasing structural ordering of the boundary layers, the friction coefficient decreases, thus widening the limits of resistance to temperature. In contrast, tribological tests of traditional carbon coatings of the amorphous structure are devoid of the above-described effect. The estimate of the total activation energy of failure of the boundary layers for steel samples with a polycrystalline coating-orientant has proved this value to be much higher than for the same steel with a coating without the orientant coating properties.     

Boundary lubrication of magnetorheological fluids in PTFE/steel point contacts

This paper is concerned with an experimental investigation of the boundary lubrication properties of magnetorheological (MR) fluids under point sliding contacts between polytetrafluoroethylene (PTFE) and stainless steel tribopairs. The tribological properties of OM, OS, OX, HS, HSI and HQ grades of carbonyl iron based MR fluids were tested using a ball-on-three plates tribometer to ascertain the optimal lubricant. Wear scars on the PTFE sheets were examined by optical microscopy, environmental scanning electron microscopy (ESEM) and energy dispersive X-ray spectroscopy (EDX) for imaging and elemental analysis of the worn surface. The research shows that OS based lubricating MR fluids have the optimal anti-wear and friction reducing properties probably due to the amorphous silica surface coating of the particles. Mechanisms by which MR fluids improve tribological behavior concern particle entrapment and (soft) surface indentation.     

Sliding wear behavior of Fe-based bulk metallic glass at high temperature

In the past decade Fe-based bulk metallic glasses (BMGs) have attracted increasing attention due to their beneficial properties, including high glass forming ability (GFA), high strength and hardness and high fracture toughness in both fundamental science and engineering application. Most research using these materials has been conducted at room temperature environment, and research that assesses their behavior especially at high temperature has been scarce. We present the results of high temperature effect on the friction and wear behavior of Fe-based bulk metallic glass (BMG), and we tested that this material may satisfy wear and oxidation resistance at high temperature as well as to explore the high temperature wear mechanism of the Fe-based BMG. The dry sliding tribological behaviors of Febased BMG against Si₃N₄ ceramic were conducted with a pin-on-disc friction and wear tribometer. The morphology of the worn surfaces of Fe-based BMG was examined by scanning electron microscopy (SEM) and the chemical composition characterized with energy dispersive spectroscopy (EDS) to observe the wear characteristics and investigate the wear mechanisms. The overall average friction coefficient value generally decreased with increasing temperature, and the glass transition and the formation of protective oxide film played an important role in the tribological behavior of BMG. The wear resistance of Fe-based BMG was not only from their hardness but also from the formation protective oxide layer. Analysis of the worn surface revealed abrasion, plastic deformation and oxidation during sliding test.     

Structure and tribological behavior of nanocomposite C-Ti-WSe x coatings

Nanocomposite thin C-Ti-WSe _x coatings, which contain antifriction (WSe _x and amorphous carbon a-C) and hard (β-WC and TiC) components, are produced by pulsed laser deposition. In order to improve the tribological characteristics of the WSe _x phase and to transform the structural state of the a-C matrix, alloying with titanium is used. The characteristics of the coatings are determined using the sliding of a steel ball at an increased humidity. A comparison of the characteristics of a composite C-Ti-WSe _x coating and a carbon coating alloyed with titanium (a-C(Ti)) shows that the modification of the a-C matrix by introducing the WSe _x phase leads to an increase in the coefficient of friction from 0.05 to 0.2; the wear of the composite coating is approximately six times higher than that of the a-C(Ti) coating. Possible solutions for improving the tribological characteristics of the composite C-Ti-WSe _x coating in humid air are considered.     

Comprehensive tribological characterization of thin TiN-based coatings

Innumerable papers have been published so far describing tribological investigations of thin hard coatings based on TiN. Analysis of the presented results demonstrates a large dispersion of measured friction and wear numbers, whereas TiN-coated pieces and tools have proved their benefits in a broad area of application. Therefore an attempt was made to clarify the influences on friction and wear test results by varying the coating process, the tribological stresses due to sliding, fretting and rolling motion and by changing the surrounding medium. The results reveal that machining of substrate surfaces and type of tribological stresses due to sliding, fretting and rolling have an important influence. The formation of reaction layers is dominating the tribological behaviour in most cases.     

Tribofilm formation and tribological properties of TiC and nanocomposite TiAlC coatings

In a recent work a concept for self lubricating low friction TiC and nanocomposite TiAlC coatings was developed. Here we further investigate the mechanical and tribological properties of these coatings. Under identical deposition conditions, the addition of Al initiates the formation of a nanocomposite consisting of (Ti,Al)C grains in an amorphous carbon matrix. The coefficient of friction is lowered from ～0.2 to below 0.1 in a pin-on-disc test against steel with unaffected coating wear rate. The lower friction is attributed to a more extensive formation of amorphous carbon and graphitisation on both the counter surface and in the coating wear track. The addition of Al also reduces coating hardness, Young's modulus and the residual stress, which can be explained by the weak carbide-forming ability of Al and the formation of a nanocomposite microstructure.     

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.     

Test Analysis of Friction Couples With Solid Lubricant Coatings under Ground–Space Conditions and Prediction of Tribological Characteristics

As a result of an analysis of the literature data on ground–space tribological tests of friction couples with solid lubricant coating (SLC) ARSRI PP 212, the dependences for evaluating the starting antifriction characteristics have been determined. The wear life and coefficient of friction have been compared. According to results, calculation algorithms of tribological characteristics of friction couples with SLC for considered operational conditions have been developed and implemented.     

Tribological behaviour of W‐alloyed carbon‐based coatings in dry and lubricated sliding contact

Carbon‐based coatings with different W contents were deposited by direct current magnetron sputtering in reactive and non‐reactive atmospheres. All deposited coatings have compact morphologies with amorphous (tungsten‐free) or nanocrystalline structures (tungsten‐doped). The latter one was indicated by very broad peaks in X‐ray Diffraction spectra in the position of tungsten carbide suggesting W‐carbide nanoparticles embedded in an amorphous carbon matrix. The hardness increased from 10 to 15 GPa with increasing W content. The coatings were tribological tested at dry and lubricated conditions with increasing temperature in a coating/steel configuration. In dry sliding, the friction coefficient increases with the increase of the temperature reaching values higher than 1.0. The friction is significantly lower in lubricated contact using three different oils: poly‐alpha‐olefin, paraffin and olive oil. The olive oil shows promising lubricating properties at the temperature lower than 70°C; however, at higher temperature, the coatings were quickly worn through. Copyright © 2014 John Wiley & Sons, Ltd.     

Properties of Coatings Based on Carbon and Nitrogen-Doped Carbon Obtained Using a Pulsed Vacuum Arc Method

Diamond-like carbon coatings on hard-alloy substrates, including coatings doped with nitrogen about 1.0 μm thick have been obtained using a pulse vacuum-arc method. Three types of coatings have been investigated: a carbon diamond-like coating (C), a carbon coating doped with nitrogen (C: N), and a composite coating based on (C: N + C) layers. The coatings have been annealed in atmospheric air at a temperature of 400°C. The tribological characteristics (wear resistance and friction coefficient change dynamics), the adhesion strength, and the microhardness of coatings in the initial state and after annealing have been studied. The composite coating consisting of C: N + C layers surpasses the constituent coatings in properties, both in the initial state and after annealing at a temperature of 400°C.     

火焰喷涂PA1010/n-SiO2复合涂层干摩擦磨损性能

利用火焰喷涂法制备PA1010/n-SiO2复合涂层,并采用均匀试验设计方法研究涂层在干摩擦条件下同GCr15 钢环配副时的摩擦学性能;利用SPSS 12.0统计软件对试验结果进行回归分析, 建立涂层摩擦系数和磨损质量损失同pv值 (摩擦载荷与摩擦速度的乘积)相关性的数学模型;利用示差扫描量热仪(Differential scanning calorimetry, DSC)和扫描电子显微镜(Scanning electron microscope, SEM)对复合涂层的热性能和磨损表面形貌进行分析。结果表明,n-SiO2的加入能明显提高涂层的结晶性能、耐磨性能。当n-SiO2含量为1.5%时,复合涂层摩擦磨损性能最佳,在试验条件下磨损质量损失降低近4倍,摩擦因数降低23％,跑合期缩短44％,复合涂层与GCr15钢环对磨时的磨损机理主要为疲劳磨损和轻微的粘附 磨损。     

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.     

Fretting wear characteristics of cold gas-dynamic sprayed aluminum alloys

Process selection for repair of mechanical components due to wear and corrosion, e.g. damage of aluminum casting housings of fuel injection systems, is based on cost and response time factors, provided that the mechanical performance is maintained within acceptable limits. One of the promising and emerging repair technologies is Cold Gas-Dynamic Spray (CGDS) coating, where a high-pressure gas propels fine powder particles to very high velocities to produce surface coating. It is essential to identify the optimum process conditions and powder composition to produce repaired surfaces with tribological properties close to those of the originally manufactured part (without coating). The objective of this work is to compare the dynamic friction and fretting wear properties of the repaired surfaces using various types of coating composition and spraying techniques. Eight types of CGDS coatings, applied to AMS 4260 aluminum specimens, were fretted against 440C stainless steel specimens at low and high nominal loads to assess their fretting wear resistance, dynamic friction properties and damping capacity. The optimum coating composition and process conditions were identified. In comparison to the uncoated specimen, this optimum coating offered tribological characteristics close to the uncoated material and even better dynamic friction properties.     

Tribological Dependence of the High-Performance Ferrous-Based Coating on Different Coating Counterparts in Engine Oil

A ferrous-based coating with significant chromium was fabricated on aluminum alloy substrate using a plasma spray technique. The tribological performance of the as-fabricated ferrous-based coating sliding against different coatings including Cr, CrN, TiN, and diamond-like carbon (DLC) in an engine oil environment were comparatively studied. Results showed that the high hardness of the sprayed ferrous-based coating was achieved due to the dispersion strengthening effect of Cr₇C₃ phase embedded in the austenite matrix. The ferrous-based coating exhibited low friction coefficients when coupled with these four coating counterparts, which could be attributed to the boundary lubricating effect of engine oil. However, both friction and wear of the ferrous-based coating were different when sliding against these different coating counterparts, which might be closely related to the surface roughness, self-lubricating effect, and mechanical properties of the coupled coatings. Ferrous-based coating sliding against CrN and DLC coatings exhibited good tribological performance in engine oil. The best coating counterpart for the ferrous-based coating in an engine was DLC coating.     

Evolution of nickel iron-based amorphous alloy structure under friction

The tribological behavior and structural transformations under friction of Ni-Co-Fe-Cr-Mo-Si-B and Ni-Fe-Si-B amorphous alloys obtained by speed hardening from melt are studied. Under unlubricated friction, crystalline layers are shown to arise on the surface of the amorphous alloys. It is concluded that the formation of a crystalline layer on the surface of the amorphous Ni-Fe-Si-B alloy of a specific atomic weight differing from the matrix phase gives rise to high extending stresses. This encourages the accelerated origination and propagation of surface cracks and decreases the alloy’s wear resistance. The amorphous Ni-Co-Fe-Cr-Mo-Si-B alloy, characterized by a higher crystallization temperature, has a higher wear resistance compared to the Ni-Fe-Si-B alloy.     

Assessment and application of TiB2 coating in sliding pair under lubrication conditions

The aim of the present work is to determine the influence of TiB₂ coating on the friction parameters in sliding pairs under lubricated friction conditions. The TiB₂ coating deposited on modified surface layers of ring specimens made of AISI 5045 steel was matched under test conditions with counterparts made from SAE-783 and SAE-48 bearing alloys. Tested sliding pairs were lubricated with 5 W/40 Lotos synthetic engine oil. Tribological properties of the TiB₂ coating were measured using a block-on-ring tribometer. The applied modification technology of the surface layer of steel allowed for obtaining construction material with pre-determined tribological characteristics required for the elements of sliding pairs in lubricated contact. The results showed differences in the wear of bearing alloys, as a result of the interaction between co-operating surface layers and of the physiochemical changes of their surfaces, induced by external forces. Friction resistance and temperature in the friction area in the pair with TiB₂ coating and the SAE-783 bearing alloy are considerably higher than in the pair with the SAE-48 bearing alloy. The SAE-48 bearing alloy is subjected to more intensive wear processes in contact with the TiB₂ coating than the SAE-783 bearing alloy.