Showing papers on "Tribometer published in 2016"

An Investigation on the Tribological Performances of the SiO2/MoS2 Hybrid Nanofluids for Magnesium Alloy-Steel Contacts.

Abstract: Hybrid nano-materials offer potential scope for an increasing numerous novel applications when engineered to deliver availably functional properties. In the present study, the SiO2/MoS2 hybrid nanoparticles with different mass ratios were employed as lubricant additives in the base oil, and their tribological properties were evaluated using a reciprocating ball-on-plate tribometer for magnesium alloy-steel contacts. The results demonstrate that the SiO2/MoS2 hybrid nanoparticles exhibit superior lubrication performances than individual nano-SiO2 or nano-MoS2 even in high load and diverse velocity cases. The optimal SiO2/MoS2 mixing ratio and the concentration of SiO2/MoS2 hybrid nanoparticles in the base oil are 0.25:0.75 and 1.00–1.25 wt%, respectively. The excellent lubrication properties of the SiO2/MoS2 hybrid nanoparticles are attributed to the physical synergistic lubricating actions of nano-SiO2 and nano-MoS2 during the rubbing process.

Wear resistance of diode laser-clad Ni/WC composite coatings at different temperatures

Abstract: Ni/WC composite coatings with different weight percentage (0–60%) of WC particle were produced on a stainless steel by diode laser-cladding technology with the aim to improve wear resistance of the stainless steel in the present study. The effects of laser power, WC particle content and rare earth element (La) on the quality of the coatings were investigated. The influences of WC content on microstructure and hardness were investigated. The friction and wear behavior of the laser-clad coatings at room temperature and elevated temperatures of 600 °C and 700 °C were evaluated using a ring-on-block tribometer. Results revealed that the laser-clad composite coatings with WC content ranging from 20 wt.% to 60 wt.% were free of cracks and pores by controlling laser power level and adding 0.4 wt.% La. An increase in WC content increases wear resistance significantly at three test temperatures except for the Ni-20% WC coating. The phase structure of the oxidation films formed during the wear test process played important role on the wear behavior of the laser-clad coatings.

Tribocorrosion behavior of veneering biomedical PEEK to Ti6Al4V structures.

Abstract: In dentistry, prosthetic structures must be able to support masticatory loads combined with a high biocompatibility and wear resistance in the presence of a corrosive environment. In order to improve the simultaneous wear and corrosion response of highly biocompatible prosthetic structures, a veneering poly-ether-ether-ketone (PEEK) to Ti6Al4V substrate was assessed by tribocorrosion analyses under conditions mimicking the oral environment. Samples were synthesized by hot pressing the PEEK veneer onto Ti6Al4V cylinders. The tribocorrosion tests on Ti6Al4V or PEEK/Ti6Al4V samples were performed on a reciprocating ball-on-plate tribometer at 30N normal load, 1Hz and stroke length of 3mm. The tests were carried out in artificial saliva at 37°C. Open circuit potential (OCP) was measured before, during and after reciprocating sliding tests. The worn surfaces were characterized by scanning electron microscopy. The results revealed a lower wear rate on PEEK combined with a lower coefficient of friction (COF), when compared to Ti6Al4V. In fact, PEEK protected Ti6Al4V substrate against the corrosive environment and wear avoiding the release of metallic ions to the surrounding environment.

The Relationship Between Friction and Film Thickness in EHD Point Contacts in the Presence of Longitudinal Roughness

Abstract: This study investigates friction and film thickness in elastohydrodynamic contacts of machined, rough surfaces, where roughness is dominated by longitudinal ridges parallel to the rolling/sliding direction. A ball-on-disc tribometer was used to simultaneously measure friction and film thickness in rough contacts as well as with nominally smooth specimens for comparison. The studied rough surfaces were selected so that the influence of the root-mean-square roughness and roughness wavelength can be assessed. Friction and film measurements were taken over a range of slide–roll ratios and speeds and with two lubricating oils with different viscosities, hence covering a wide range of specific film thicknesses. The measurements with the nominally smooth specimens show that friction is strongly influenced by thermal effects at high SRRs and that the transition from mixed/boundary to full EHD lubrication occurs at lambda ratios greater than three. At low speeds, the rough specimens are found to generate higher friction than the smooth ones for all the roughness structures considered, and this is shown to be related to the thinner minimum film thickness. Comparison of friction in rough and smooth contacts shows that the total friction in rough contacts can be divided into two components: one that is equivalent to friction in smooth contacts under the same conditions and is dependent on the slide–roll ratio, and the other that is due to the presence of roughness and is independent of the slide–roll ratio under the conditions tested. Further analysis of the minimum film thickness on tops of roughness ridges indicates that even after the full lift-off, an effect of the roughness on friction persists and is most likely related to the local shear stress in the micro-EHD contacts on the top of roughness ridges. At even higher speeds, the difference in friction between the rough and smooth specimens vanishes.

Development and evaluation of low friction TiSiCN nanocomposite coatings for piston ring applications

Abstract: To minimize the frictional losses and wear of piston rings in an automotive engine, thick low friction TiSiCN nanocomposite coatings have been developed. The coatings were deposited by sputtering titanium targets in argon, nitrogen, hexamethyldisilazane (HMDSN), and acetylene (C 2 H 2 ) using plasma enhanced magnetron sputtering (PEMS). The substrates were AISI 304 stainless steel coupons and piston rings with bore diameters of 137 mm and 86 mm. The elemental composition and microstructure of the coatings were optimized by varying the HMDSN and C 2 H 2 flow rates separately to achieve a combination of excellent adhesion, good mechanical properties, low coefficient of friction (COF) and wear rate. The optimized TiSiCN coatings exhibited a typical nanocomposite structure which showed excellent adhesion and dry COF in the range of 0.17 to 0.2 using a ball-on-disk tribometer. The tribological performance of the coated piston rings was evaluated using Plint TE77 tests in SAE 10W-30 diesel engine oil. The TE77 tests showed a 10% reduction in the COF (0.058) of the optimized coating compared to the uncoated baseline (0.065) at test conditions of 20 Hz, 30 N, and 25 mm stroke length. Finally, the coated rings were evaluated in a single cylinder gasoline engine using SAE 5W-20 engine oil and in a heavy duty diesel engine using 4.1% sooted SAE 10W-30 diesel engine oil. The gasoline engine test showed that the uncoated piston rings contributed 25% to 34% of the frictional loss in two separate baseline engine tests. In contrast, the coated rings contributed to 18% of the total frictional loss in the engine test. The diesel engine durability test showed a 28% and 40% lower ring weight loss for the coated top and second rings, respectively, as compared to the uncoated baseline. In addition, the cylinder liner, which was not coated, showed an average 50% lower wear than that in the uncoated baseline engine test.

Water-lubricated Ni-based Composite (Ni-Al2O3, Ni-SiC and Ni-ZrO2) Thin Film Coatings for Industrial Applications

Abstract: In this work, pure nickel and Ni-based nanocomposite coatings (Ni–Al2O3, Ni–SiC and Ni–ZrO2) were produced on steel substrate by using pulse electrodeposition technique. The industrial performance tests were conducted to evaluate the wear resistance, corrosion resistance, adhesion strength and wettability behaviour of newly developed coatings. Rolling contact ball-on-disc tribometer was used to assess anti-wear behaviour of these coatings under water-lubricated contacts. The results showed that the wear- and corrosion resistance properties of nickel alumina and Ni–SiC composite coatings significantly improved than that of pure Ni and Ni–ZrO2 coatings. The adhesion and wettability results of Ni–Al2O3 composite showed better performance when compared to the rest of the coatings. The effects of incorporating nanoparticles on the surface microstructure, interface adhesion and distribution of the particles were also investigated. The coatings were characterized by using scanning electron microscopy, X-ray diffraction analysis and 3D white light interferometry. The wear failure behaviour of these coatings was further examined by post-test surface observation under optical microscope.

Tribological behavior of UHMWPE against TiAl6V4 and CoCr28Mo alloys under dry and lubricated conditions

Abstract: This work is focused on the study of the tribological behavior of TiAl6V4 and CoCr28Mo against UHMWPE. Wear tests were achieved on a reciprocating pin-on-disc tribometer under dry and lubricated conditions. Four bio-lubricants were retained namely: saline solution (NaCl 0.9%), sesame oil, nigella sativa oil and Hyalgan® which is a pharmaceutical intra-articular injection containing sodium hyaluronate active agent (20mg/2mL). The coefficient of friction and wear volume of UHMWPE were evaluated after tribological tests. It is found that, the friction and wear behaviors of CoCr28Mo/UHMWPE pair under dry and bio-lubrication were the best. Results show that the use of natural oils improved significantly the tribological behavior of CoCr28Mo/UHMWPE and TiAl6V4/UHMWPE pairs. Microscopic and chemical analyses of wear tracks on UHMWPE were carried out and wear mechanisms were proposed for each materials pair. The tribological performance of the used oils was linked to their chemical composition and to their adsorption ability on the metallic surfaces.

Effect of hexagonal boron nitride nanoparticles as an additive on the extreme pressure properties of engine oil

Abstract: Purpose This paper aims to investigate the effect of hexagonal boron nitride (hBN) nanoparticles on extreme pressure (EP) properties when used as an additive in lubricating oil. Design/methodology/approach The nano-oil was prepared by dispersing an optimal composition of 0.5 vol. per cent of 70 nm hBN in SAE 15W-40 diesel engine oil using a sonication technique. The tribological testing was performed using a four-ball tribometer according to the ASTM standard. Findings It was found that the nano-oil has a potential to decelerate the seizure point on the contact surfaces, where higher EP can be obtained. More adhesive wear was observed on the worn surfaces of ball bearing lubricated with SAE 15W-40 diesel engine oil as compared with the nano-oil lubrication. Originality/value The results of the experimental studies demonstrated the potential of hBN as an additive for improving the load-carrying ability of lubricating oil.

Corrosion and tribocorrosion behavior of Ti-B4C composite intended for orthopaedic implants.

Abstract: Poor wear resistance of titanium is a major concern since relative movements due to the cyclic loads in body environment cause wear between the bone and the implant material leading to detachment of the wear debris and release of metal ions due to the simultaneous action of corrosion and wear, defined as tribocorrosion. In order to increase the tribocorrosion resistance, Grade 2 Ti matrix 24vol% B4C particle reinforced composites were processed by hot pressing. Corrosion behaviour was investigated by electrochemical impedance spectroscopy and potentiodynamic polarization in 9g/L NaCl solution at body temperature. Tribocorrosion tests were performed under open circuit potential, as well as under potentiodynamic polarization using a reciprocating ball-on-plate tribometer. Results suggested that the addition of B4C particles provided lower tendency to corrosion and lower corrosion kinetics under sliding, along with significantly reduced wear loss, mainly due to the load carrying effect given by the reinforcement particles.

Tribological Behavior of Aluminum Hybrid Composites Studied by Application of Factorial Techniques

Abstract: This article analyzes the influence of graphite reinforcement, load, sliding speed, and sliding distance on tribological behavior of A356 aluminum matrix composites reinforced with silicon carbide and graphite using the full-factorial design. The wear rates of A356/10SiC composite material and A356/10SiC/1Gr and A356/10SiC/3Gr hybrid composites have been analyzed. The composites were obtained by a modified compocasting procedure. Tribological tests were performed on a block-on-disc tribometer without lubrication. The testing included sliding speeds of 0.25 and 1.0 m/s, normal loads of 10 and 20 N, and sliding distances of 300 and 900 m. The analysis of the obtained results was performed using the full-factorial method based on the signal-to-noise (S/N) ratio. The effects of load, sliding speed, weight percentage of graphite reinforcement, and sliding distance on the wear rate are 38.99, 17.87, 13.95, and 11.25%, respectively. The best tribological characteristics were exhibited by the A356/10SiC/1...

Optimization of Wear Behavior of Magnesium Alloy AZ91 Hybrid Composites Using Taguchi Experimental Design

Abstract: In the present paper, the statistical investigation on wear behavior of magnesium alloy (AZ91) hybrid metal matrix composites using Taguchi technique has been reported. The composites were reinforced with SiC and graphite particles of average size 37 μm. The specimens were processed by stir casting route. Dry sliding wear of the hybrid composites were tested on a pin-on-disk tribometer under dry conditions at different normal loads (20, 40, and 60 N), sliding speeds (1.047, 1.57, and 2.09 m/s), and composition (1, 2, and 3 wt pct of each of SiC and graphite). The design of experiments approach using Taguchi technique was employed to statistically analyze the wear behavior of hybrid composites. Signal-to-noise ratio and analysis of variance were used to investigate the influence of the parameters on the wear rate.

The Friction Reducing Effect of Square-Shaped Surface Textures under Lubricated Line-Contacts—An Experimental Study

Abstract: Surface texturing has been shown to be an effective modification approach for improving tribological performance. This study examined the friction reduction effect generated by square dimples of different sizes and geometries. Dimples were fabricated on the surface of ASP2023 steel plates using femtosecond laser-assisted surface texturing techniques, and reciprocating sliding line contact tests were carried out on a Plint TE77 tribometer using a smooth 52100 bearing steel roller and textured ASP2023 steel plates. The tribological characterization of the friction properties indicated that the textured samples had significantly lowered the friction coefficient in both boundary (15% improvement) and mixed lubrication regimes (13% improvement). Moreover, the high data sampling rate results indicated that the dimples work as lubricant reservoirs in the boundary lubrication regime.