Abstract: Visioplastic analyses with the rod technique were performed in the extrusion of AA6060 alloy at different processing conditions in order to measure the friction effect at the billet-container interface. During the trials an accurate monitoring of the relevant process variables such as punch force and temperatures was performed in order to validate FEM simulations. Different FE codes were used to carry out the simulations: Deform, HyperXtrude, and Superform. A particular attention was given on evaluating the several coefficients of the available friction models by comparing the FEM results with experimental results.

Abstract: The present study investigates the combined influence of surface texture, using sinusoidal, positive full and half wave roughness (transverse and longitudinal roughness) and non-Newtonian lubricants, obeying power law model on finite journal bearing. The modified Reynolds equation is solved numerically through finite difference approach for analysis of texture and non-Newtonian effects on bearing performance characteristics. It is concluded that the load carrying capacity and friction force is increased with shear thickening fluids in both bearings (smooth and rough bearings). It is also concluded that out of three roughnesses, the transverse positive full wave roughness is best for increasing the load carrying capacity and friction force, whereas the longitudinal sinusoidal roughness is best for decreasing the friction force.

Abstract: A tribological test for deep drawing has been developed by which the performance of lubricants may be evaluated quantitatively measuring the maximum backstroke force on the punch owing to friction between tool and workpiece surface. The forming force is found not to give useful information regarding the lubricant performance, since it is not sensitive enough to reveal changes in the frictional contact, whereas the backstroke force is very sensitive to pick-up and galling even on micro-scale. Results from testing different lubricants with different performances are found to be consistent with visual judgement of the resulting surface of the drawn cups.

Abstract: The non-linear region of polarisation curve near the corrosion potential can be discussed depending on data of over potential as a function of current densities. These data can be analysed by suggesting a mathematical model taking into account the effect of mass transfer on activation process. This model was used to evaluate the values of polarisation resistance Rp in presence and absence of potassium iodide (KI) as a corrosion inhibitor of low carbon steel in 2.5 M phosphoric acid at different temperatures. The values of polarisation resistance obtained by mathematical model compared with these obtained by Tafel parameters. The suggested s-model was very useful in evaluating the values of Rp. The maximum value of polarisation resistance was 5049.13 Ωcm² at 30°C in presence of 0.05 M KI, while the minimum value was 1.885 Ωcm² at 60°C in absence of KI. These results indicate that the polarisation resistance values increased with the increase of KI concentration, and decreased with the increase of temperature.

Abstract: AISI H13, a typical material used for hot extrusion dies, is gas nitrided using automated two-stage controlled nitriding process with the aim to evaluate the controlled nitriding process on nitride layer formation in terms of morphology, case depth and hardness variation across the nitride layer. A sequentially coupled thermal-diffusion analysis of actual nitriding cycle is performed numerically using finite element code, ABAQUS. The results show that the growth of nitride layer and the nitrogen concentration distribution in the diffusion zone can be accurately predicted numerically in close agreement with experimental results. The influence of nitriding time, temperature and potential is studied and it is found that these parameters significantly affect the nitride layer formation in terms of nitrogen concentration and hardness variation as a function of nitride case depth.

Abstract: Ni59Zr16Ti13Si3Sn2Nb7 amorphous material was deposited by laser cladding onto Ti-3Al-5Mo-5V-4Cr-2Zr titanium alloy. Despite trials with wide range of process parameters, the present experiments were unable to retain complete amorphous surface microstructure after laser cladding. So the mixed structure with amorphous phase, intermetallic compounds and borides were obtained. XRD results showed that the amorphous phase fraction of the coatings was measured up to about50% depending on the laser cladding parameters. DSC curve showed that glass transition temperature (Tg) and crystallization temperature (Tx) was observed around 750K and 880K, respectively, which indicated that the Ni-based amorphous alloy coating had high thermal stability. The nanocrystalline grains, were about 40-100nm in size, precipitated from amorphous phase or interface between amorphous and borides. The Vickers hardness of coating depended on the amount of various phases that were present in different locations of coating.

Abstract: Nanocomposites based on SiO2 nanoparticles dispersed in a PMMA matrix have been successfully prepared and submitted to tribological tests and c11 measurements by Brillouin spectroscopy, so that to explore the elastic and wear behaviour of the material compared to pure PMMA. We show that the elastic constant and the stick-slip may be clearly different depending on the rate and the chemical bonding treatment of the nanoparticles. Correlation between these parameters is also discussed.

Abstract: Nano-structured C-Ni coatings were prepared using the thermionic vacuum arc method and tribological properties were evaluated in order to obtain carbon-metal layers to act as solid lubricants. The C-Ni films prepared by TVA method were characterised as a metallic complex of nano-crystals (5 nm average diameter) surrounded by carbon amorphous structures with a strong graphitisation tendency. The coefficients of friction of the coatings, measured using a CSM ball-on-disc tribometer, were in the range of 0.19-0.27 3-5 times lower than the uncoated substrates.

Abstract: Micro-lubricant pockets located in the surface of plastically deforming workpieces are recognised to improve the performance of fluid lubrication in a metal-forming process. This work investigates the joint influence of pocket geometry and process working conditions on micro-lubrication mechanisms, during upsetting and strip drawing, by means of a rigid-viscoplastic finite-element formulation. Special emphasis is placed on the effect of pocket geometry on the build-up of hydrostatic pressure, which is responsible for the onset of micro-lubrication mechanisms. A good agreement is found between the numerically predicted and the experimentally measured distributions of hydrostatic stress.

Abstract: Surface coatings increase the wear and smearing resistance of a machine element. Nevertheless, most of the coating processes are expensive and time-consuming. By contrast, Schaeffler's Durotect® B coating seems attractive regarding production expenditure and price. However, the literature about the behaviour of this coating is very limited. This paper describes the experimental setup and the experiments that were carried out in order to evaluate the wear and smearing resistance of the Durotect® B coated 100Cr6 steel in reference to plain 100Cr6 through hardened steel. Durotect® B is a mixed black iron oxide coating developed by Schaeffler especially for use in machine elements. The main measured parameters (mass loss, smearing slide-to-roll ratio, friction and normal force, surface roughness and bulk temperature) are presented. Comparative charts of the monitored parameters are given and discussed. It is concluded that this coating decreases friction coefficient and improves both the smearing and wear resistance.

Abstract: Electroless nickel?phosphorus coating has been deposited onto plain carbon steel specimens by using an alkaline bath based on NiCl2 as source of nickel cations. The tribological behaviour under dry non-lubricated conditions has been evaluated by employing the pin-on-disc test method. Two surfactants namely sodium dodecyl sulphate and cetyl trimethyl ammonium bromide were added to the EN bath for the first time in the similar kind of study. The influence of the surfactants on the hardness, friction and wear behaviour of the coatings was investigated and compared against the samples produced without addition of surfactants.

Abstract: This paper deals with the problem of tribological failure of artificial knee prostheses. The clinical problem is introduced by analysis of worn knee bearings made of ultra-high molecular weight polyethylene. Three different failure mechanisms are described: subsurface-originated contact fatigue failure, surface-originated wear of the articulating surface, and surface-originated wear of the back (non-articulating) surface. The wear processes were simulated in a rolling/sliding wear tester built for this specific purpose. The influence of gamma-irradiation dose on wear and contact fatigue was determined. Wear was greatest at the portion of the wear track where the lubricating fluid film was thinnest and a boundary or mixed lubrication regime prevailed.

Abstract: Ni-CeO2 nanocomposite coatings were fabricated by a novel method from a modified Watt’s type electrolyte containing CeO2 nanoparticles with an average particle size of 30 nm, where an ultrasonic field was imposed during electrodeposition process. Surface morphologies of the coatings were examined by a scanning electron microscope (SEM) with energy dispersive analyzer system (EDX) to determine the composition of nanocomposite coatings. The crystal structure of coatings was characterized by employing the X-ray diffraction (XRD). Vickers hardness of nanocomposite coatings was measured with a microhardness tester. The wear resistance of Ni-CeO2 nanocomposite coatings and pure Ni coating was comparatively investigated on a UMT-2MT test rig in a ball-on-disk contact mode. It was found that the Ni-CeO2 nanocomposite coating with ultrasonic irradiation exhibited grain structure with finer and compact crystal of Ni matrix compared to pure Ni and the Ni-CeO2 nanocomposite coating without ultrasonic irradiation. The crystal orientation of Ni-CeO2 nanocomposite coatings greatly changed in presence of ultrasound. Furthermore, the imposition of ultrasound gave rise to increasing the hardness and wear resistance of the Ni-CeO2 nanocomposite coating. The results could be considered as the effects of nanoparticles embedded and ultrasonic irradiation and the finer-grain structured coating resulted. The improvement in the wear resistance of Ni-CeO2 nanocomposite coatings can be attributed to the grains refinement of Ni matrix in presence of ultrasound as well as the dispersion-strengthening effect to some extent. Because of the aid of ultrasound, the co-deposited CeO2 nanoparticles were uniformly distributed in Ni matrix and contributed to largely increase the microhardness and wear resistance of the nanocomposite coatings.

Abstract: A new field 'engineered surfaces' would be a more effective and economic route to successful manufacture. Low plasticity burnishing (LPB) is a method of surface enhancement, which raises the burnishing to next level of sophistication and that can provide deep, thermally stable surface compression for improved surface integrity characteristics. Some of the surface characteristics which could be improved from LPB technology are: surface finish, surface microhardness, low- and high-cycle fatigue strength, corrosion resistance and wear resistance. However, in the current research work, full factorial, orthogonal design of experiments were conducted on AISI 1045 and AISI 316L work materials, using a newly designed LPB tool to evaluate the effect of LPB parameters on the surface integrity. The assessment of the surface integrity aspects on work materials was done by evaluating the interaction effects of parameters. Mathematical expressions were developed for response variables. Subsurface microhardness studies were also done to assess the depth of compression.

Abstract: Strategic stainless steel surfaces have been developed for which the tribological properties are significantly improved for sheet-metal forming compared with the as-received surfaces. The improvements have been achieved by modification of the surface to promote Micro-Plasto Hydrodynamic Lubrication (MPHL) by increasing the ratio of closed lubricant pockets and modifying the pocket geometry. These factors influence the retention and subsequent escape of lubricant during forming thus enhancing lubricant permeability to the contact between flattened workpiece asperities and contacting tool. The technique, which has been developed, is based on an electrochemical treatment changing the topography of the stainless steel surface. Comparative testing of the new surface topographies in ironing and deep drawing of stainless steel sheet shows significant improvements and possibilities of replacing chlorinated paraffin oils with environmentally friendly plain mineral oil.

Abstract: In lubricated contacts, the fluid film protects and separates the two contacting surfaces. Depending on the pressure and on the surface velocities, different lubricated regimes can occur. These different lubricated regimes are successively described and some pictures show their occurrence in different contacts.

Abstract: Titanium and its alloys are mainly to be found in the aerospace field in which their high strength to density ration is particularly attractive. However, their quite poor behaviour in most of the encountered tribological situations, especially fretting remains a limiting factor. The objective of this research was to determine the effect of an oxygen-diffusion hardening process by laser on the surface morphology, microhardness and scratch resistance of commercially pure titanium. Pure titanium substrates have been treated using a pulsed Nd: YAG laser radiation. The repetition of laser shots at the surface of the titanium induces the progressive oxidation and to the formation of oxygen-diffusion coatings. The treated layers have been characterized by optical and SEM observation, X-ray diffraction analysis and scratch test. The oxygen-diffusion hardened samples were obtained in present work. The treated samples were more resistance to scratch damage compared to the non-treated samples. The presence of the surface coating structure has been examined in relation with the Ti-O phase diagram and consisted of an harden TiO2 surface layer.

Abstract: Although the lowering engine oil viscosity is effective to improve the fuel efficiency of automobiles, its research has not been advanced because of the concern about a plain bearing lubrication. The plain bearing performance was evaluated with low viscosity base oils using a newly developed apparatus which enables the simulation under the automotive conditions. As a result, it was found that the friction coefficient and the contact condition between the plain bearing of Cu-Pb alloy and the shaft were different from that of Al-Si alloy. It is important to consider the plain bearing materials for the design of engine oils.

Abstract: Carbon nitride (CNx) films were prepared on silicon substrates by pulsed laser arc deposition with different working gases and various gas pressures. The bonding structure and the chemical compositions of the resulting CNx films were studied by AES, Raman spectroscope and XPS, respectively. The results showed that the average nitrogen content varied between 9% and 28%, and masses of sp² C?N bond and sp³ C?N bond formed in the CNx films. The nanohardness decreased from 30 GPa to 6 GPa, whereas the friction coefficient increased with increasing nitrogen content in the resulting CNx films.

Abstract: The operating conditions in power station boilers are conducive to erosion, both in the furnace wall and in the super heater and reheater areas, and these effects cause tube wall thinning and premature failure. The present research work has been undertaken with an objective to explore the coating potential of Al2O3-3 wt% TiO2 deposited on boiler steel T11 with detonation gun spraying process for erosion resistance. Erosion performance at room temperature as well as elevated temperature by simulating the temperature to actual working conditions of the boilers was evaluated. The eroded samples were analysed with SEM/EDX and optical profilometer.

Abstract: Laser gas assisted nitriding improves the properties of steel surfaces through grain refinement and nitride compounds formation in the surface region. In the present study, laser gas assisted nitriding of tool steel (H13) is carried out. The microstructural and morphological changes in the laser nitrided region are examined using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The first and second law efficiencies of the laser nitriding process are formulated using the lump parameter analysis. It is found that the depth of nitride layer extends 60 μm below the surface. The nitrided layer is free from cracks and voids. The first and second law efficiencies reduce with increasing laser power; however, they increase significantly with increasing laser scanning speed.

Abstract: Ni-Cr based alloy were fabricated using powder metallurgy method. It was found that the composites were mainly consisted of nickel-based solution, chromium sulfide et al., the strengthening phases can improve the hardness of alloy obviously, but decreases the bending strength. Both the wear and friction of alloy with strengthening phase was improved.

Abstract: This paper presents a macro/micro scale finite-element local-refinement model developed in order to analyse mixed-lubrication conditions in Internal Combustion (IC) big-end conrod bearings. The initial coarse mesh is refined in the mixed-lubrication contact zones to obtain a good-enough representation of the contact pressure. The flow factor method and a statistical elasto-plastic asperity contact model are included. The results show important differences between the classical TEHD and the local-refinement model, especially in the estimation of the asperity contact pressure.

Abstract: The fundamental characteristics of the taper seal used to prevent oil leakage from fluid bearings were analysed theoretically and investigated experimentally. The three-dimensional flow field was theoretically analysed using numerical fluid dynamics, and the profile of the oil meniscus was calculated using the balance between the pressure field and surface tension. The oil meniscus was experimentally investigated using a micro-focus laser microscope. Three triggers for oil leakage were identified: the oil contact angle on the sleeve surface becoming excessive, the convex portion of the meniscus profile extending beyond the edge of the sleeve, and cavitation occurring in the oil.

Abstract: Both characterisation of wear debris and identification of wear debris from lubricating oils and greases in the tribological systems were investigated in the present paper. The characterisation system to describe wear debris morphology was erected based on the identification parameters of wear debris in the ferro-graphic system. Four characterisation parameters were analysed, including colour, surface texture, shape and size of wear debris. By using grey fixed weight clustering method, six kinds of wear debris were recognised, i.e., normal wear debris, ball particles, cutting debris, sever sliding debris, debris of Fe2O3 and Fe3O4, which is helpful to pre-diagnose the fault type of machinery.

Abstract: This paper presents the effects of surface coating on the wearing resistance of cold forging tools used for manufacturing fixing parts. The wear of test specimens was analysed with and without coating. The titanium carbonitride, titanium nitride and chrome nitride coating were obtained by Physical Vapour Deposition. The coatings were also tested for two different kinds of tools: a trimming die and an extrusion die used in manufacture of fixing parts. The wearing behaviour was observed at industrial scale during the manufacturing process. The best wearing resistance was found for titanium carbonitride coating in both laboratory and industrial scale.

Abstract: Fe-based metallic glass coatings were prepared on Ti?3Al?5Mo?5V?4Cr?2Zr substrate by Air Plasma Spraying (APS) The effect of spraying power (arc current) on amorphous phase content and properties of the coatings was investigated It was revealed that the coating sprayed at arc current of 150 A was nearly fully amorphous although the spraying powders were not The amorphous phase content in the coatings decreased with increasing arc current Vickers microhardness and corrosion behaviour of the sprayed coatings were also studied The highest cross-section microhardness of the coatings was Hv005908, roughly three times as high as that of the substrate The coating sprayed at arc current of 300 A exhibited the best excellent corrosion resistance

Abstract: The present paper aims to assess the friction coefficients obtained with pin-on-disc tests against those acquired in mechanical processing of materials, under similar conditions of surface texture and to evaluate the role of the mechanical properties of the pin-on-disc tribo-pairs in the overall frictional behaviour. It is shown that pin-on-disc tests, when performed with an adequate control of surface texture, are capable of providing a good estimate of the average value of the friction coefficient in mechanical processing applications and, in certain cases, when the tribo-pairs have similar mechanical properties, the value of the friction coefficient is independent of surface morphology.

Abstract: UHMWPE resin powder was blended with a-tocopherol and these blends were consolidated to prepare the UHMWPE samples by compression molding method. Then these samples were irradiated by gamma-irradiation. Accelerated aging was performed on some of the samples. The effects of a-tocopherol on the wear behavior and mechanical properties of the gamma-irradiated and α-tocopherol doped UHMWPE specimen were investigated. The hardness, scratch coefficients and ultimate tensile strength (UTS) of a-tocopherol doped, irradiated UHMWPE specimen were higher than irradiated UHMWPE specimen; the α-tocopherol doped, irradiated UHMWPE specimen showed lower wear rate than irradiated UHMWPE specimen. Accelerated aging decreased the ultimate tensile strength and increased the wear rate of irradiated UHMWPE samples significantly, while affected the α-tocopherol doped, irradiated UHMWPE specimen slightly.