Mating Materials Research Articles

Analysis of Nanoscale Wear Particles from Lubricated Steel–Steel Contacts

A new method for sampling wear particles directly from the lubricant reservoir has been developed and applied successfully for analyzing wear particles by high-resolution scanning electron microscopy in transmission mode having coupled energy-dispersive X-ray spectroscopy. The lubricated tribological testing was carried out with fully formulated as well as with non-formulated synthetic base oil. It was possible to analyze individual particles with dimensions as small as about 5–30 nm which are likely the “primary” wear particles. A majority of the particles, however, are agglomerated and, thus, lead to the formation of larger agglomerates of up to a few micrometers. Chemical analysis led to the conclusion that most of the observed particles generated in formulated oil, especially the larger ones, are composed of the additives of the lubricant oil. In non-formulated base oil, the primary particles are of similar dimensions but contain only iron, chromium and oxygen, but most likely stem from the mating materials. This finding points to the fact that the main wear mechanism under lubricated conditions with fully formulated oil is more like a continuous shearing process rather than a catastrophic failure with the generation of larger primary particles. When the oil is non-formulated, however, several wear mechanisms act simultaneously and the wear rate is increased significantly. Generated larger primary particles are milled down to the nanoscale. When the oil is fully formulated, wear mainly takes places at the additive layer or tribofilm; thus, the steel surface is protected.

Improvement on Sliding Wear Behavior of Al/Cast Iron Tribopair by CNT's Reinforcement of an Al Alloy

The results presented in this work show the wear characterization of Al-Si matrix composites reinforced by multiwall carbon nanotubes (MWCNTs) under dry reciprocating sliding conditions against a grey cast iron (GCI) The wear resistance is investigated as a function of the carbon nanotube (CNT) content that varied from 2 to 6 wt%. The results demonstrated that the CNT content plays a relevant role in the wear behavior by substantially reducing the wear loss of Al-Si CNT composites. Further, it reduces the wear loss of the grey cast iron counterface. A physical model able to explain the improved behavior in both mating materials is depicted from experimental results.

Predominant factor determining wear properties of β-type and (α+β)-type titanium alloys in metal-to-metal contact for biomedical applications

The predominant factor determining the wear properties of a new titanium alloy, Ti–29Nb–13Ta–4.6Zr (TNTZ) and a conventional titanium alloy, Ti–6Al–4V extra-low interstitial (Ti64) was investigated for TNTZ and Ti64 combinations in metal-to-metal contacting bio-implant applications. The worn surfaces, wear debris, and subsurface damages were analyzed using a scanning electron microscopy combined with energy-dispersive spectroscopy and electron-back scattered diffraction analysis. The volume loss of TNTZ is found to be larger than that of Ti64, regardless of the mating material. The wear track of TNTZ exhibits the galled regions and severe plastic deformation with large flake-like debris, indicative of delamination wear, which strongly suggests the occurrence of adhesive wear. Whereas, the wear track of Ti64 have a large number of regular grooves and microcuttings with cutting chip-like wear debris and microfragmentation of fine oxide debris, indicative of abrasive wear combined with oxidative wear. This difference in the wear type is caused by severe and mild subsurface deformations of TNTZ and Ti64, respectively. The lower resistance to plastic shearing for TNTZ compared to that of Ti64 induces delamination, resulting in a higher wear rate.

Synthesis and characterization of AlTiSiN/CrSiN multilayer coatings by cathodic arc ion-plating

Abstract AlTiSiN/CrSiN multilayer coatings were deposited on Si (1 0 0) and cemented carbide substrates using Cr, AlTi cathodes and SiH 4 gases by cathodic arc ion plating system. The influences of SiH 4 gases flowrate on the structural and mechanical properties of the coatings were investigated, systematically. AlTiSiN/CrSiN coatings exhibit a B1 NaCl-type nano-multilayered structure in which the CrSiN nano-layers alternate with AlTiSiN nano-layers with multiple orientations of crystal planes indicated by XRD patterns and TEM. Si contents of the coatings increase with increasing SiH 4 flowrate. The hardness of the coatings increases to the maximum value of 3500 Hv 0.05 with increasing SiH 4 flowrate from 20 to 40 sccm and then decreases with further addition of SiH 4 gases. A higher adhesive force of 73 N is obtained at the flowrate of 48 sccm. The coatings exhibit different tribological performance when the mating materials were varied from Si 3 N 4 to cemented carbide balls and the variation of friction coefficients of the coatings against Si 3 N 4 influenced by SiH 4 flowrate are not obvious as against cemented carbide balls.

순수 알루미나와 탄소나노튜브 강화 알루미나 복합체의 극초단 펄스레이저 가공특성 비교

In this paper, pure <TEX>$I_{ph}$</TEX> and hybrid carbon nanotube reinforced <TEX>$I_{ph}$</TEX> were sintered using the SPS(spark plasma sintering) method for high densification. A nanosecond laser (<TEX>${\lambda}=1063nm$</TEX>, <TEX>${\tau}P=10ns$</TEX>) and a femtosecond laser (<TEX>${\lambda}=1027nm$</TEX>, <TEX>${\tau}P=380fs$</TEX>) were installed on an optical system for the micromachining test. The ablation characteristics of the pure <TEX>$I_{ph}$</TEX> and CNT/<TEX>$I_{ph}$</TEX> composites, such as thermal effect and ablation depth, were investigated using FE-SEM and a confocal microscope device. Laser machining results for the two mating materials showed improved performances: CNT/<TEX>$I_{ph}$</TEX> composites showed good surface morphology of hole drilling without a melting zone due to the composites' high thermal properties; also, the ablated depth of CNT/<TEX>$I_{ph}$</TEX> was higher than that of pure <TEX>$I_{ph}$</TEX>.

Adhesion and friction force measurements in ambient and high vacuum conditions

Physical insight into the frictional behaviour of surfaces in contact with vacuum and other special environments is important for the accuracy of positioning mechanisms operating in these environments. The positioning accuracy and drift in these mechanisms are strongly infl uenced by the frictional behaviour of the mating materials. The cause for both drift and positioning accuracy is stick-to-slip and slip-to-stick transitions at asperity level, resulting in a displacement at macrolevel. Adhesion as well as friction experiments were performed for single asperity and multi-asperity contacts both in ambient and high vacuum conditions on a novel designed vacuum-based adhesion and friction tester. This paper discusses the experimental setup designed and manufactured to investigate the adhesion and friction behaviour of a single asperity contact. The intrinsic roughness of the ball and the fl at will form a multiasperity contact. Pull-off and friction force measurements can be performed with the resolution better than 5 μN. The maximum normal load that can be applied with this system is 100 mN. The setup is capable of working at 10 -6 mbar vacuum level as well as in ambient conditions. Experimental results show that the surrounding environment and roughness play an important role both in the adhesion force and friction force measurements. The friction force measurements show good agreement with the basic theories of contact mechanics.

Toward Low Friction in High Vacuum for Hydrogenated Diamondlike Carbon by Tailoring Sliding Interface

The high friction of diamondlike carbon (DLC) films in vacuum impedes achieving their application in space environment. Here we show that the vacuum friction coefficients can be lowered below 0.1 by avoiding formation of carbonaceous transfer layers on the counterfaces. First-principles calculations reveal that the low friction coefficients stem from intrinsically weak-interacting sliding interfaces. Conversely, formation of transfer layers and carbonaceous sliding interfaces thus established are invalid for friction reduction for DLC in vacuum. The mating materials are thus highlighted for their crucial roles in transfer-layer formation.

Facile wear failure monitoring of commercial bearing alloys using I-kaz method

Numerous methods have been well developed in the area of bearing monitoring. This paper presents an experimental study of wear monitoring of connecting rod bearings type AA7075-T6 within audio frequency signals; f<20kHz against a AISI4340 hardened steel via air-borne with the aid of tribometer. The objective of this study is to determine the correlation between the noise signals and wear responses via air-borne method generated due to the sliding wear action. The wear tests were carried out by using a pin-on-disc configuration at a range of sliding speed 5.24, 7.85 and 9.95m/s. A set of sliding distance was utilised, ranging from 20 to 160km at a fixed load of 200N. The test was performed under a lubricated sliding condition using a SAE40 type lubricant to imitate the actual operation of the connecting rod bearings. Presented results were obtained using a microphone 40SC type which was located 10mm from the pin-on-disc contact. The extracted noise was represented as numerical descriptor of I-kaz coefficient, Z̵∞ using MATLAB software. From the analysis, it was noted that the specific wear rate K′, value was proportional to an increase of sliding velocity in which K′ lies in between 1.36 and 7.96×10−8mm3/Nm. Based on the morphology investigation, it was found that under a lubricated test, parallel grooves and craters up to 10μm in size were present, indicating the occurrence of the abrasive action of fresh abrasive action caused by the entrapment of hard debris particles that protruded soft mating materials thus, resulting a higher coefficient of friction. Oxides formation in adhesive junction was attributed to yield a lower friction, and this was clearly supported by X-ray diffraction spectra on worn surfaces. Furthermore, from the microstructure observation of worn surfaces it was also strongly suggested that a combination of adhesion, abrasion, fatigue and delamination wear mechanisms had occurred. Detailed changes in wear responses were analysed and displayed in I-kaz™ 3D spaces. This approach is capable of determining bearing condition, thus allowing the end-user to monitor the wear rate and the degradation of the bearings.

Solid-state bonding of alloy-designed Cu–Zn brass and steel associated with phase transformation by spark plasma sintering

Solid-state bonding between steel and a Cu alloy was studied to investigate fabrication of advanced bimetallic composites by using spark plasma sintering (SPS). In order to obtain proper bonding strength between the mating materials, Si and Al were alloyed to Cu–Zn brass to enhance interdiffusion with steel. The alloying elements diffused from the Cu alloy to steel, which transformed from the gamma to alpha phase during bonding. Owing to the phase stability of steel, the new columnar microstructure that evolved during the transformation across the joint interface showed high bonding strength between the mating alloys. The samples bonded without fracture, defects, or inhomogeneous deformation. Microstructural observations, elementary mapping, and mechanical testing demonstrated that the SPS technique and specific bonding parameters enhanced the interdiffusion between the metals. This novel method would be well suited to strengthen bonding between two dissimilar metals with different diffusion coefficients.

Tribological properties of DLC films against different steels

We studied the effect of mating materials on the tribological properties of DLC film using mating materials of martensite stainless steels (hardened and annealed AISI440C), austenite stainless steel (AISI304), and bearing steels (hardened and annealed AISI52100). The reciprocating sliding tests were performed with ball-on-plate friction tester in dry air. Analyses of friction surface of specimens were carried out using optical microscopy and micro-laser Raman spectroscopy.With the exception of the annealed AISI52100 ball, the friction coefficient of DLC film decreased with increasing normal load. The friction coefficient for the annealed AISI52100 ball showed a high friction coefficient under wide normal load conditions. Analysis using micro-laser Raman spectroscopy showed that the difference between annealed AISI52100 and others materials appears mainly due to structural changes in the film. Tribological properties of DLC film may thus be affected by a property change in mating materials rather than by mating ball hardness.

Friction, wear and tribofilm formation on electrical contact materials in reciprocating sliding against silver-graphite

In this study nanocomposite coatings mating silver-graphite were investigated for sliding electrical contact applications with the aim to optimize tribological and electrical properties. Apart from two different Ti–Ni–C nanocomposite coatings, brass, steel and TiN were also tested against a commercial silver-graphite at varying load and current. Friction, wear and contact resistance were measured in reciprocating sliding in ambient air. It was concluded that the wear of the silver-graphite was increased by current, for TiN and steel as much as four times, at a 5N load. A tribofilm, with properties differing from the silver-graphite, formed on the coating/metal surface in all cases. This resulted in a very similar coefficient of friction, 0.3, for all mating materials. However, different load and current gave rise to slightly different thickness and morphology. A too low load was detrimental, as the coating became damaged, while a too high load was not favorable for tribofilm formation. In tests with varying current, a specific current could be identified that best governed the build-up of a well conducting and stable tribofilm. The largest differences were observed in the initial stages of testing, since once the tribofilm was built up, the contact resistance approached that of self mated silver-graphite, 40mΩ. Experiments showed that the load and the current can be optimized to minimize wear of the silver-graphite which in turn would allow for lower maintenance costs.

Vacuum tribological performance of DLC-based solid–liquid lubricating coatings: Influence of sliding mating materials

The friction and wear behaviors of DLC-based solid–liquid lubricating coatings for three liquid lubricants sliding against different counterface materials were examined under high vacuum conditions. Seven kinds of balls with the diameter of 3mm were chosen as counterparts, which were GCr15, bronze, ZrO2, Al2O3, SiC, WC, and Si3N4. Under high vacuum condition, the friction coefficient (COF) and wear rate of carbon-based solid–liquid lubricating coatings sliding against different counterparts were diverse, due to different liquid lubrications and counterface materials. In analyzing the friction and wear mechanism, the contact radius and the contact pressure were introduced. The COF showed the inverse varied trend with Hertzian contact radius for the three liquid lubricants. COF decreased with the increase of contact radius, which was different from the dry sliding of DLC film. The possible reason was that the synergetic lubrication between the DLC films and the liquid lubricants formed a new solid–liquid synergistic system (DLC-oil-DLC), which improved the ability of plasticity-resistant deformation, reduced the real contact area and friction coefficient. The contact pressure was consistent with the wear rate varied trend for the three liquid lubricants, and this varied trend was in good agreement with each other for MACs lubricant.

Influence of relative slip on fretting fatigue behaviour of 2014 aluminium alloy with the age-hardened conditions T4 and T6

The present work deals with the effect of relative slip on fretting fatigue behaviour of 2014 Aluminium alloy with age-hardened conditions T4 and T6 in contact with a dissimilar mating material AISI 1045 steel, using a plane-on-plane configuration. There are a significant number of parameters influencing fretting fatigue behaviour. Relative slip value between the specimen and fretting pad is one of the most important factors. In the present study, the influence of relative slip was evaluated at different cyclic stress levels by using a fretting pad with a single pad span value of 10 mm. The results show the artificial temper T6 is more effective for improving the fretting fatigue life when compared with natural temper T4. This may be attributed to a higher microstructural barrier to the fretting fatigue crack nucleation and initiation, due to having lower values of relative slip with artificial temper T6.

Investigation of the dynamic response in a dry friction process using a rotating stick–slip tester

In this paper, the friction stability of brake materials is investigated by means of a rotating stick–slip tester. Experimental results are compared with a computational model implemented in Simulink. The main goal of this work is to find out how vibrations induced by friction are related to mechanical system parameters such as inertia (mass), stiffness, damping and sliding speed. At the same time, a computational model is developed in order to analyse the dynamic response of a dry friction process at different conditions. A friction sample with nominal contact area of 254 mm2 was subjected to sliding against a gray cast iron disk. The sliding speed was varied between 0.28 and 10 mm/s, while the normal load was kept constant (400 N, equivalent nominal pressure 1.57 MPa). Moreover, tests were carried out in three different damping values and two different stiffnesses. Experimental results show typical stick–slip behaviour for the lowest speeds while for the highest speeds stick–slip disappears and smooth sliding prevails. The computational model can be used to evaluate the dynamic response in dry friction process, as far as static/dynamic coefficient of friction of the mating materials are known as well as the mechanical characteristics of the system.

Influence of SiC addition on tribological properties of SiAlON

The tribological properties of gas pressure sintered SiAlON and its composite with 18 wt% silicon carbide (SiC) against two different mating materials, i.e., alumina and SiAlON are evaluated. SiAlON and SiAlON–18%SiC composite ceramics were prepared by pressure less sintering and gas pressure sintering. Fretting wear tests were carried out under dry unlubricated ambient conditions (room temperature 23–25 °C; relative humidity 50–55%) with a load of 8 N for 45,000 cycles. Friction and wear properties of SiAlON–SiC proved better than the monolithic SiAlON. The formation of silica roll like structure on the composite worn surface was observed.

Impact of Wire-EDM on Tribological Characteristics of ZrO2-based Composites in Dry Sliding Contact with WC–Co-Cemented Carbide

The effect of surface conditions and secondary phase addition on the dry sliding friction and wear characteristics of five yttria-stabilized ZrO2-based composites with 40 vol% WC, TiCN or TiN was investigated using an ASTM G133 pin-on-flat sliding contact configuration. WC–6wt%Co-cemented carbide pins were used as mating material. The friction and wear level were higher for wire-EDMed ZrO2-based composites compared to their equivalent ground specimens. This finding could be correlated to flexural strength measurements, revealing strong discrepancy between wire-EDMed and ground surfaces. The most favorable tribological characteristics were encountered with ZrO2–WC composites compared to ZrO2–TiCN and ZrO2–TiN grades.

Performance of CrN radical nitrided tools on deep drawing of advanced high strength steel

The performance of CrN film coating to reduce adhesion in the forming process of advanced high strength steel (AHSS) sheets was investigated. Radical nitriding prior to CrN film coating was used to increase the bond strength between the thin film coating and the tool steel substrate. Electron probe microanalysis was used to characterize nitride diffusion into the tool steel. Scratch testing was carried out to evaluate the bond strength between film coatings (CrN, TiN radical nitride and CrN radical nitride) and the substrate. Ball-on-disk testing was carried out to determine the friction coefficient. Deep drawing experiments with non-coated and coated tools were performed on SPFC 980Y steel sheets. JIS-SKD11 tool steel and TiN-coated tools exhibited high friction under dry sliding with SPFC 980Y sheet material. Moreover, severe adhesion was observed in deep drawing experiments using these mating materials. CrN film showed no adhesion to SPFC 980Y sheet material. The bond strength between a CrN film and the substrate can be increased by a nitride layer before coating.

Micro CNC surface texturing on polyoxymethylene (POM) and its tribological performance in lubricated sliding

The effect of surface texturing on the friction of polyoxymethylene was investigated in terms of surface texturing density. Surface texture was machined using CNC machining. Five different surface texturing densities were machined and tested in a pin-on-disk sliding configuration. Bearing steel was used as a mating material on polyoxymethylene (POM). Sliding speed and nominal contact pressure were 0.1 m/s and 1.35 MPa, respectively. Sliding distance was 1 km, and the lubricant was SAE 5W-30 oil. The lowest coefficient of friction was obtained with a 10% texturing density, where the reduction in friction was about 50% of that of the non-textured POM.

Investigation of bipolar plate and diffusion media interfacial structure in PEFCs: A fractal geometry approach

The imperfect interfacial contact between the bipolar plate (BP) and the diffusion medium (DM) can have a significant impact on the multi-phase flow and current transport in an operating polymer electrolyte fuel cell (PEFC). The objective of this work is to describe the impact of the BP and DM surface morphologies and the resulting interfacial contact on PEFC performance. In this study, the surface morphology of several BP and DM samples was digitally characterized using optical profilometry (OP). The benchmark surface data were then utilized in a microscopic model developed to simulate the BP|DM interfacial contact under compression. The microscopic model is based on the fractal modeling approach, which provides an accurate representation of the BP|DM interfacial contact by suppressing the resolution dependence of the surface profiles in consideration. Results indicate that the uncompressed surface morphology of mating materials, elasticity of these components, and local compression pressure are the key parameters that influence the BP|DM contact. The model results show that the void space along the BP|DM interface can potentially store a significant amount of liquid water (from 0.85 to 3.5 mg/cm 2), which can result in reduced durability and performance of the PEFC. The model predicts that a 50% drop in the DM surface roughness results in nearly a 40% drop in the BP|DM contact resistance and a 15% drop in the BP|DM interfacial water storage capacity.

Fretting fatigue behaviour of hard anodizing coated 2014-T6 aluminium alloy with dissimilar mating materials under plane bending loading

The effect of hard anodizing coated 2014-T6 aluminium alloy test samples with dissimilar mating materials on fretting fatigue was investigated. Fretting fatigue configuration involved bridge-type pads on the flat specimen. Bridge-type pads were made of AISI 4140 steel. All the fretting fatigue tests were conducted under plane bending loading with a stress ratio of R = —1. Coated and uncoated specimens were compared for microhardness, surface roughness, tangential force. The specimens were tested under both plain fatigue and fretting fatigue loading at ambient temperature. Micrographs obtained from scanning electron microscope showed that hard anodizing coating had tiny cracks through the thickness of the anodized layer. The hardness of hard anodized coating was higher than that of uncoated specimens and they also exhibited lower tangential force. However, the fretted region of the hard anodizing coated specimens was rougher than that of uncoated samples and despite lower tangential forces, fatigue lives of hard anodizing coated samples were inferior to those of uncoated samples. As the hard anodizing coating had pre-existing tiny cracks and tension residual stress, cracks propagated from the hard anodizing coating through the interface into the substrate. We conclude that these may be the main reasons for inferior fretting fatigue lives compared with uncoated samples.