Worn Surface Morphology Research Articles

Nano-wear-induced behavior of selective laser melting commercial pure titanium

In this work, the nano-wear-induced behavior of selective laser melting (SLM) processed commercial pure titanium was investigated under several applied loads from 1 mN to 100 mN. The dense (over 99%) commercial pure titanium sample was manufactured using SLM process with optimized process parameters (900 J m-1). Nano-wear testing was performed on the polished surface of SLM processed commercial pure titanium. The friction coefficient increased from 0.04 to 0.9 as the load increased from 1 mN to 100 mN. Additionally, the sliding behavior changed along with the applied loads, from elastic to plastic and unstable friction behaviors. The elastic-plastic transition appeared at applied load of 50 mN, which was also confirmed by the calculation results. While the applied load ranged between 50 mN and 80 mN (plastic friction), the average friction coefficient was light smaller than that of the macroscopic ball-on-disc test. During the sliding, a friction vibration appeared and its mechanism was also investigated and discussed combine the wear surface morphologies.

Dry sliding wear response of ZrB2-20vol.% MoSi2 composite

Abrasive wear behavior of ZrB2- 20 vol.% MoSi2 composite has been studied using electroplated diamond disk as the counter facing body. The investigated composite has been prepared by hot pressing and it has been found to possess 97% of the theoretical density. The microstructure of the composite has been characterized using scanning electron microscopy (SEM), and results show that MoSi2 particles are uniformly distributed in the ZrB2 matrix. The Young’s modulus, Poisson’s ratio and fracture toughness of the investigated composite are 455 GPa, 0.11 and 4.7MPa√m, respectively. The effect of experimental conditions including applied load, sliding velocity and sliding distance on the tribological behavior of ZrB2- 20 vol.% MoSi2 composite have been investigated. Experimental results show that applied load and sliding velocity plays an important role on specific wear rate and surface roughness of worn surfaces. SEM is used to analyze the wear surface morphology and crack propagation to study the wear mechanism. The dominant mode of wear was identified as abrasion. Grain pullout and micro cracking control the prevailing wear mechanism.

Design and Simulation Analysis of Micro-Porous Structure in Infiltration-Type Self-Lubrication Composites Matrix

Metal ceramic preforms were fabricated by vacuum sintering method in this work. Ti–Fe–Cr–W–Mo–V powder was used as the basic material, TiH2 and CaCO3 were used as the composite pore-forming material and Al2O3 was used as dispersal particles. The microstructure and the worn surface morphology of the preforms and the composites were analyzed using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The experimental results showed that when the micro-pore shapes are circular and quadrilateral respectively, with the increasing load, the Mises equivalent stress distribution generated by the single cell model is quite different, but it has symmetry, and the maximum stress appears around the interpenetrating micro-pore. Using FeCrWMoV alloy powder as the metal phase and TiC powder as the ceramic phase, the micro-porous matrix was prepared by powder metallurgy sintering with the addition of a certain volume fraction of compound pore-making agent.

Modeling and prediction of optimal process parameters in wear behaviour of selective inhibition sintered high density polyethylene parts

Owing to the dependency of multiple process parameters in additive manufacturing (AM) techniques, it is tedious to determine optimal processing conditions for improving quality characteristics of fabricated functional pats. The present study focuses on optimization of four key contributing parameters such as layer thickness, heater energy, heater feedrate, and printer feedrate on dry sliding wear behaviour of high-density polyethylene (HDPE) parts fabricated through a novel selective inhibition sintering (SIS) process. The experiments are conducted on the basis of response surface methodology (RSM) and four factor-three level box-behnken design. The significance of the developed models and contribution of each process parameters on wear rate are estimated through analysis of variance (ANOVA). The results suggested that wear rate is influenced principally by the layer thickness and heater energy. The quadratic regression model of RSM associated with the desirability approach is employed to determine optimum levels of process parameters. The morphologies of worn surfaces are observed using scanning electron microscope. Sensitivity analysis has been performed to measure the relative impact of SIS process parameters on wear rate.

Influence of polyphenyl ester and nanosized copper filler on the tribological properties of carbon fibre–reinforced ultra-high-molecular-weight polyethylene composites

Ultra-high-molecular-weight polyethylene (UHMWPE) reinforced with carbon fibre (CF) and filled with polyphenyl ester (POB) and nanosized copper (Cu) fillers was prepared by compression moulding. The tribological behaviours and the synergism of the incorporation of fibre and particulates were studied. The proportions of the reinforcement material ranged from 5 wt% to 25 wt%, the filler material of POB varied from 5 wt% to 25 wt% and the nanosized filler was from 4 wt% to 12 wt%. In the sample with CF only, the lowest wear rate was observed for the UHMWPE + 15% CF composite. The particulate filler further reduced the composite wear rate, and the lowest wear rate was found for the hybrid with CF, POB and nanosize Cu particles, that is, for the UHMWPE + 15% CF + 15% POB + 12% Cu composite. The particulate filler was added, and the coefficient of friction slightly increased. The transfer film formed on the metal counterface was studied using optical microscopy, and the topography of the transfer film was investigated using atomic force microscopy. Results showed that the transfer films were thin, compact and uniform on the metal counterfaces of the UHMWPE + 15% CF + 15% POB + 12% Cu composite. Worn surface morphologies of composites were studied using scanning electron microscopy. Results showed that the worn surface of the UHMWPE + 15% CF + 15% POB + 12% Cu composite was smoother and had better wear resistance than that of other composites.

Tribological and Vibration Studies on Newly Developed Nanocomposite Greases Under Boundary Lubrication Regime

Greases are widely used in extreme conditions of load, speed, and temperature, altogether with the improvement in the service life of the machinery by reducing the noise and vibration. The present study deals with the development of nanocomposite greases and their tribodynamic evaluation under boundary lubrication (BL), antiwear, extreme pressure (EP), and vibration behavior of nonconformal metallic contacts. The recording of the vibration signals constitutes the indirect approach to evaluate the lubricity of the tribological contacts. The different nano-additives (reduced graphene oxide (rGO) nanosheets, CaCO3, and α-Al2O3 nanoparticles) are dispersed in commercial lithium grease to formulate nanocomposite greases. The microstructural studies of greases are performed on high-resolution transmission electron microscopy (HRTEM). The BL behavior is studied using four ball tester. Further, the functional groups of the greases and the chemistry of the worn surfaces are evaluated through Raman spectroscopy (RS). To explore the involvement of wear mechanism(s), the morphology of worn surfaces is evaluated using scanning electron microscopy (SEM). The results showed that doping of 0.4% rGO and 5% CaCO3 in bare lithium grease can significantly improve the antiwear, EP properties, and vibration behavior, compared to α-Al2O3 dispersed composite grease.

Tribological properties of nanometer cerium oxide as additives in lithium grease

This paper presents a comparative study of the influence of nanometer-CeO2 (nano-CeO2) and temperature on tribological and lubricating properties of lithium grease. The morphology and structure of nanocrystals were characterized by means of transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively. Friction and wear tests were conducted on the friction and wear tester. Results show that the lithium grease with addition of nanometer-CeO2 has much better friction-reducing and anti-wear performance than that of base grease. When the additive in grease is 0.6 wt%, the friction coefficient (COF) and wear scar diameter (WSD) decrease by 28% and 13% comparing with base grease, respectively. The base grease and grease with 0.6 wt% nanometer-CeO2 both possess the lowest average COF and wear width at 50 °C. The worn surface morphology after friction test was analyzed by scanning electron microscopy (SEM) and NANOVEA three-dimensional profilometer. Under the lubrication of the lithium grease containing 0.6 wt% nano-CeO2, few shallow furrows can be observed on the quite smoothed surface and the WSD decreased. Moreover, It was found that the nano-CeO2 has been incorporated into the surface protective and lubricious layer by energy dispersive spectrometer (EDS) analysis.

Abrasive wear of polypropylene/Cloisite 30B/Elvaloy AC 3427 nanocomposites

Polymer nanocomposite may be defined as a structure that is formed by infusing at least one dimension of the dispersed particles in the nanoscale range into a thermoplastic polymer matrix. Polypropylene/Cloisite-30B/Elvaloy-AC3427 nanocomposites were manufactured by melt intercalation method using a twin screw extruder. X-ray diffraction shows an intercalated structure of nanocomposite category. The investigation of tribological properties of polypropylene/Cloisite-30B/Elvaloy-AC3427 nanocomposite material has enormous practical importance to ascertain the friction and wear values. In the tribological study, the two-body abrasive wear was conducted with input parameters (Cloisite-30B, load and sliding distance) and output parameters (wear loss, specific wear rate and coefficient of friction) at 0.5 m/s sliding velocity. The detailed validation of the abrasive wear volume with mechanical properties (tensile strength, elongation at break and shore d hardness), and the dominant factors of abrasive wear by analysis of variance and worn surface morphology by Scanning Electron Microscope were reported.

Fretting Wear Behaviors of Aluminum Cable Steel Reinforced (ACSR) Conductors in High-Voltage Transmission Line

This work reports the fretting wear behavior of aluminum cable steel reinforced (ACSR) conductors for use in high-voltage transmission line. Fretting wear tests of Al wires were conducted on a servo-controlled fatigue testing machine with self-made assistant apparatus, and their fretting process characteristics, friction force, wear damage, and wear surface morphology were detailed analyzed. The results show that the running regime of Al wires changes from a gross slip regime to a mixed regime more quickly as increasing contact load. With increasing amplitudes, gross slip regimes are more dominant under contact loads of lower than 30 N. The maximum friction force is relatively smaller in the NaCl solution than in a dry friction environment. The primary wear mechanisms in dry friction environments are abrasive wear and adhesive wear whereas abrasive wear and fatigue damage are dominant in NaCl solution.

Enhancement of surface properties with influence of bath pH on electroless Ni-P-ZnO/Al2O3 nano-composite deposits for defence applications

The focus of this paper is to experimentally investigate the effect of ENi-P-ZnO/Al2O3 composite deposition on corrosion and wear resistance, surface morphology, crystallographic structure, microhardness, surface roughness (Ra) and wettability, on mild steel specimen, by maintaining bath pH at 5, 7 and 9. On investigation, it is revealed that incorporation of ZnO and Al2O3 sharply improves the corrosion resistance, microhardness, coefficient of friction, wear rate, surface roughness and morphology of the as-deposited samples as against nondeposited mild steel specimen. Incorporation of ZnO nanoparticles results in 96% reduction in corrosion rate (7.92mmpy) as against the without deposited mild steel specimen (180mmpy) and incorporation of Al2O3 nanoparticles results in 184% increase in microhardness (625Hv) as against the without deposited mild steel specimen (220Hv), under optimum operating conditions of bath pH7 and pH9 respectively, thereby enhancing applications in various defence fields like marine and aviation.

Friction and wear properties of an automobile brake lining reinforced by lignin fiber and glass fiber

PurposeThis paper aims to thrash out friction and wear properties of automobile brake lining reinforced by lignin fiber and glass fiber in braking process.Design/methodology/approachABAQUS finite element software was used to analyze thermo-mechanical coupled field of friction materials. XD-MSM constant speed friction testing machine was used to test friction and wear properties of friction material. Worn surface morphology and mechanism of friction materials were observed by using scanning electron microscope.FindingsThe results show that when the temperature was below 350°C, worn mechanism of MFBL was mainly fatigue wear and abrasive wear, and worn mechanism of GFBL was mainly fatigue wear because MFBL contained lignin fiber. Therefore, it exhibits better mechanical properties and friction and wear properties than those of GFBL.Originality/valueLignin fiber can improve mechanical properties and friction and wear properties of the automobile brake lining.

Effect of applied load on transition behavior of wear mechanism in Cu−15Ni−8Sn alloy under oil lubrication

Tribological behavior of Cu−15Ni−8Sn (mass fraction, %) alloy against GCr15 ring under various loads was investigated on a ring-on-block tester in oil lubrication. The results showed that the wear rate increased slowly from 1.7×10−7 to 9.8× 10−7 mm3/mm under the load lower than 300 N, and then increased dramatically to the climax of 216×10−7 mm3/mm under the load over 300 N, which indicated the transition of wear mechanism with the increase of applied load. The wear mechanism mainly was plastic deformation and abrasive wear under the load less than 300 N. As the applied load was more than 300 N, the wear mechanism of Cu−15Ni−8Sn alloy primarily was delamination wear. Besides, the transition can also be confirmed from the different morphologies of worn surface, subsurface and wear debris. It is distinctly indicated that the appearance of flaky debris at the applied load over 300 N may be a critical point for the change of wear mechanism.

Comparisons of tribological properties between laser and drilled dimple textured surfaces of medium carbon steel

PurposeThe study aims to compare tribological properties between laser dimple textured surface and drilled dimple textured surface, and to analyze the influence of dimple hardened edges and ability of trapping wear debris on wear properties of dimple textured surfaces.Design/methodology/approachCircular textured dimples were produced on AISI 1,045 specimen surfaces using laser surface texturing (LST) and drilled surface texturing (DST) methods. Tribological behaviors of LST, DST and non-textured specimens were studied using ball-on-disc tribo-tester. Metallographic structures, dimples and worn surface morphologies were observed using a three-dimensional digital microscope. Hardnesses of substrate and dimple edges were measured.FindingsThere was no obvious difference in wear and friction coefficients between LST and DST specimens. Hardnesses of laser dimple edges were much higher than that of drilled dimple edges and specimen substrate. The hardened materials of laser dimple edge included recast zone and heat affect zone. Laser dimple was cone-shaped and drilled dimple was cylinder-shaped. Drilled dimple had a better ability of trapping wear debris than laser dimple. Non-uniform wear phenomenon occurred on worn surfaces of LST dimple specimens.Originality/valueThe ability of textured dimples to trap wear debris is affected by single dimple volume. Hardened edges of dimples cause non-uniform wear on worn surfaces of LST specimens.

Influence of wollastonite shape and amount on tribo-performance of non-asbestos organic brake friction composites

In the present investigation, applicability of wollastonite as a potential non-asbestos based fibre/filler cum friction modifier is explored taking in to account the shapes of the wollastonite used for manufacturing the brake friction composite. Hence, brake friction composites containing wollastonite in the form of powder and fibres are prepared and characterized for their physical, mechanical and tribological properties. Experimental results indicated that wollastonite in the form of powder, improve the coefficient of friction and fade performance, whereas wollastonite in the form of fibres enhanced the wear and recovery performance of these brake friction composites. The wear surface morphology of the friction composites having wollastonite fibres aided in the formation of smooth contact plateaus which are in turn beneficial in decreasing the wear. From the study it is clear that not only judicious selection of ingredients for making brake friction composites is important but also their shapes help in formulating composites having desired friction and wear attributes.

A Strategy for Preparing Modified Graphene Oxide with Good Dispersibility and Transparency in Oil

The challenges of graphene as a high-performance additive applied in lubricant are its dispersibility and transparency. Herein, oleic diethanolamide borate (ODAB)-grafted graphene oxide nanosheets (GO) with good dispersibility in oil were successfully achieved. The structure analysis of the as-prepared ODAB-grafted GO (MGO) nanosheets verified that the molecular ODAB has bonded with the active groups of the GO nanosheets surface, as determined by characterizations. In addition, the tribological properties of the MGO nanosheets as lubricant additive applied in oil were evaluated by a friction-testing machine, and the morphologies of worn surfaces were observed by 3D laser scanning microscope. The results showed that the MGO nanosheets possessed excellent dispersibility and transparency in oil, while the friction coefficient and wear scar diameter (WSD) of the MGO-based oil with 0.02 wt % MGO content decreased to about 38.4% and 42.0% less than those of the base oil, respectively.

Hydrophobic and tribological behaviors of a poly(p‐phenylene benzobisoxazole) fabric composite reinforced with nano‐TiO2

ABSTRACT1H,1H,2H,2H‐Perfluorooctyl trichlorosilane (PFTS) was used to modify TiO2 nanoparticles, and hydrophobic PFTS–TiO2 nanoparticles were obtained by an ultrasonic reaction method. The PFTS–TiO2 surface morphological and hydrophobic properties were analyzed with scanning electron microscopy (SEM), Fourier transform infrared spectrometry, and contact angle (CA) testing. Then, the poly(p‐phenylene benzobisoxazole) fabric–phenolic composite filled with PFTS–TiO2 as a lubricant additive was fabricated by a dip‐coating process. The tribological properties of the composite were investigated, and the wear surface morphology was observed by SEM. The experimental results show that the water CA of the composite filled with PFTS–TiO2 was 158°, and the composite containing 4 wt % PFTS–TiO2 exhibited excellent antifriction and abrasion resistance. The hydrophobic surface of the composite showed excellent durable performance with a static water CA of 126.7° after abrasion. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45077.

Tribological properties and mechanisms of self-mated ultrafine-grained titanium

While titanium and its alloys have an excellent balance of properties, they continue to have limited applications owing to their relatively poor wear resistance, in particular for commercially pure titanium. Processing by severe plastic deformation (SPD) has been developed over the last two decades that produces an ultrafine-grained (UFG) microstructure resulting in improved mechanical properties. However, only limited studies are available to date on the wear behavior of SPD-processed UFG metallic materials with many conflicting results in terms of reduced wear rates. Furthermore, the wear behavior and mechanisms of SPD-UFG metallic materials are unknown in self-mated sliding contacts. Here, the friction and wear properties of self-mating UFG titanium in a cross-cylinder high frequency reciprocating contact is reported and compared to coarse grain (CG) titanium. Cross-sectional focused ion beam microscopy, transmission electron microscopy, and Raman spectroscopy studies were performed inside worn surfaces to determine the dry sliding wear-induced structural and chemical evolution responsible for the observed friction coefficients and wear rates. It was determined that the microhardness of UFG titanium increased from 2.6 to 3.4GPa; however, this increased hardness did not correlate to lowering of friction and wear. Instead, the similar friction coefficients and wear rates of CG titanium and UFG titanium were due to similar wear surface structures and oxide debris composition. Furthermore, wear surface morphologies and cross sections inside the wear tracks revealed that CG titanium had a major shear deformation contribution to wear, but with the wear rates being equivalent, wear is most likely dominated by oxide particle abrasion.

Effect of alumina content on microstructures, mechanical, wear and machining behavior of Cu-10Zn nanocomposite prepared by mechanical alloying and hot-pressing

In the present research work, novel (Cu-10Zn)100-x – x wt.% Al2O3 (x = 0, 3, 6, 9 & 12) nanocomposites were manufactured by mechanical alloying process followed by vacuum hot-pressing technique. The mechanical properties (sinterability, hardness and compressive strength), wear behavior (coefficient of friction, wear rate and worn surface morphology) and machining behavior (surface roughness and chip thickness) were explained and investigated elaborately. The same compositions of (Cu-10Zn)100-x – x wt.% Al2O3 microcomposites (coarse crystalline matrix alloy reinforced with alumina) were also fabricated and compared with nanocomposites. It was observed that uniform distribution and embedding of nano-alumina in the nanocrystallite (nano-grain) matrix in nanocomposites were achieved which exhibited excellent performances. The (Cu-10Zn)88–12 wt% Al2O3 bulk nanocomposite produced highest compressive strength which was around 9.4 times higher than the same amount of reinforcement of microcomposites. Further, nanocomposites showed lower value of coefficient of friction and surface roughness which means a considerable wear resistance and good surface finish was obtained in nanocomposites.

Influence of Multiple Bionic Unit Coupling on Sliding Wear of Laser-Processed Gray Cast Iron

In this study, in effort to improve the sliding wear resistance of gray cast iron under wet lubrication conditions, specimens with different bionic units were manufactured and modified according to bionic theory. Inspired by the structure and appearance of biological wear-resistant skin, two kinds of bionic units were processed by laser on the specimen surfaces. We investigated the wear resistance properties of the samples via indentation method and then observed the wear surface morphology of specimens and the stress distributions. The results indicated that coupling the bionic units enhanced the wear resistance of the cast iron considerably compared to the other samples. We also determined the mechanism of wear resistance improvement according to the results.

Tribological properties and lubricating mechanism of SiO2 nanoparticles in water-based fluid

The tribological properties of surface modified SiO2 nanoparticles suspension in water-based lubricant have been studied. SiO2 (30 nm) nanoparticles were dispersed through surface modification with polyethylene glycol-200. Transmission electron microscope (TEM) and infrared (IR) spectroscopy show that SiO2 nanoparticles disperse well and stably in the water-based lubricant. The diameter of the nanoparticles is about 60 nm. Tribological properties of the water-based lubricant were evaluated using four-ball wear test machine and pin-on-disk tester under different loads and different concentrations of SiO2 nanoparticles. Wear surface morphology, element chemistry configuration of steel balls and steel rings were studied by means of X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Results show that the tribological properties of the water-based fluid have been improved by addition of nanoparticles ranging from 0.1% to 0.3% concentrations. SiO2 nanoparticles deposited onto the wear surface during the sliding, which helped to reduce the friction coefficients and increase the anti-wear properties due to the miniature ball bearing effect and self-repairing performance of nanoparticles between the friction pairs. With the increase of test load, the friction coefficients decrease but the wear of the surface increase.