Sliding Wear Tests Research Articles

Experimental and numerical investigation on the wear behavior of high performance railway wheel steels paired with various brake block materials under dry sliding conditions

Sliding wear tests were carried out with a pin-on-disc machine to study the tribological behavior of EN ER7 and AAR CLASS B wheel steels paired with cast iron and organic composite brake block materials. The contact stress was 0.61 MPa and the sliding speeds were 0.52 m/s and 0.62 m/s. The wear behavior was related to the friction coefficient recorded during the tests, the specific wear rate calculated at the end of the experiments and the microhardness profile obtained on the cross-section of the wheel pins. The worn surface and cross-section of the pins were analyzed by optical and scanning electron microscopy to investigate the main damage mechanisms. A stationary finite element model was proposed to estimate the contact temperature of the pin. The test results showed the same damage mechanisms for both steels, such as oxidative wear, delamination, abrasive wear and material transfer from the brake disc to the wheel pin, which led to adhesive wear. Overall, ER7 steel performed better when paired with the composite material as the pins showed lower specific wear rate; on the contrary, CLASS B pins had lower specific wear rate when the counterpart was cast iron. The tribological behavior of both steels was not influenced by the sliding speed. The simulations showed that the contact temperature was always higher when the disc in composite material was used, regardless of the pin material. Furthermore, ER7 steel demonstrated lower contact temperatures than CLASS B due to the lower friction coefficients in the experiments.

Optimization of Sliding Wear Parameters for Copper Surface Composites Reinforced with AlCoCrCuFe HEA

The present research pacts with fabrication of Cu – HEA surface MMC through solid state Friction Stir process (FSP) and analysis of wear characteristics. AlCoCrCuFe HEA with higher hardness values vacillated up in the level of 770HV is selected as reinforcement. The wear test is performed for 16 parameter combinations based on Taguchi method with the aid of Pin-on-Disc apparatus. The input parameters considered are HEA percentage, applied load, sliding velocity and distance whereas wear rate and coeffi cient of friction are chosen as response. WR signifi cantly decreases with HEA additions and increases with increase in load, sliding velocity and sliding distance. The consequence of HEA addition on CoF during dry sliding wear test is contradictory to its effect over WR. ANOVA results confi rmed the signifi cant effect of reinforced HEA over wear characteristics of copper composite. TOPSIS methodology is followed to fi nd the best possible parameter combination that yields better wear rate and coeffi cient of friction.

Modified Method for Determination of Wear Coefficient of Reciprocating Sliding Wear and Experimental Comparative Study

A modified method for predicting the wear coefficient of reciprocating sliding wear was proposed in this study, which is less time-consuming. Based on this method, reciprocating sliding wear tests of three chain alloys (CM490, SS316, and TC4) under different loadings were conducted and the friction coefficient, wear coefficient, and wear morphology were obtained and compared. The results indicated that the time-variant coefficient of friction (CoF) could be used as an indicator for the stable wear state; moreover, it also changes periodically with the wear direction. Statistical analysis of friction coefficient indicated that it follows bimodal distribution or multimodal distribution. The friction and wear behaviors of CM490 and SS316 were different from those of TC4, and a detailed micro-morphological analysis indicated that the discrepancy is caused by the difference in the quantity and size of the wear debris. Furthermore, an upper limit of the contact stress-dependent wear coefficient was also observed, and the variability of the wear coefficient was also analyzed.

Dry sliding wear behaviour of ZrB2-based ceramics: Self-mated and cross coupling with alumina

Systematic dry sliding wear tests with monolithic ZrB2 and Al2O3 pins coupled to ZrB2, ZrB2-20 vol% SiC and Al2O3 discs were carried out in a disc-on-pin configuration. The steady state friction of ZrB2 self-mated or cross coupled with Al2O3 was about 1.1. Self-mated monolithic ZrB2 discs worn about three orders of magnitude more than self-mated Al2O3 discs. ZrB2 pin wear rate was almost double when coupled to ZrB2 or ZrB2-20 vol% SiC discs than when coupled to Al2O3 discs. The wear track of ZrB2-based materials showed an oxygen increment due to humidity-driven tribo-reaction. In all the systems, the main wear mechanisms observed were microfracture and abrasion. Numerical calculations and fracture models were employed to describe the wear mechanisms. By nanoindentation tests on worn and unworn areas, a significant lower hardness of the debris layer formed when ZrB2 materials were involved.

Microstructural characteristics and tribological behavior of an additively manufactured Ti-6Al-4V alloy under direct aging and solution-aging treatments

Direct aging and solution-aging treatments were implemented on a laser powder bed fusion-processed Ti-6Al-4V alloy to enhance its tribological performance. Dry sliding wear tests over a wide range of normal loads (2.5–40 N) and sliding velocities (50–800 rpm) were employed to investigate their comprehensive wear behavior. The results indicate that high-density Ti3Al precipitates were formed, and the decomposition of α'→α + β occurred during the aging treatments. A higher aging-hardening response of the studied alloy was achieved after the β solution treatment relative to the as-built state. The worn morphologies and wear mechanisms depend significantly on the microstructural characteristics, applied loads, and sliding velocities.

Investigations on Dry Sliding Wear Behavior of a Wire Arc Additively Manufactured Nickel-based Superalloy

ABSTRACT Wire Arc Additive Manufacturing (WAAM) is a low-cost method of fabricating large components from advanced materials such as nickel-based superalloys. Nickel-based superalloys have varied industrial applications and suit the WAAM method due to their excellent weldability when used in conjunction with metal inert gas welding equipment used in the current study. All WAAM specimens were subjected to a standard dry sliding wear test to examine wear behavior. During the wear study, load, sliding velocity, and sliding distance were all considered for both wrought and WAAM alloy. The lowest wear was observed at a lower load and higher sliding velocity, whereas the highest wear was observed at a higher load and lower sliding velocity. Wear mechanisms and wear debris corresponding to lowest and highest wear conditions were also being investigated. The transition from lowest to highest wear rate in both alloys was attributed to the transition from abrasive to adhesive and delamination wear mechanisms. Microstructure analysis revealed that the nickel-based WAAMed alloy had an equiaxed dendritic structure, whereas the nickel-based wrought alloy had a cellulose structure. Both specimens had a stable austenite structure in the Ni-Fe-Cr phase, as determined by X-ray diffraction analysis. The X-ray diffraction line profile analysis technique by the Williamson-Hall relationship revealed that WAAM alloys have higher micro-strain, higher dislocation density, and smaller crystallite size when compared to wrought alloys. The experimental results showed a 23% increase in hardness and a considerable improvement in wear resistance in the WAAMed alloy compared to the wrought alloy.

Reciprocating sliding wear behavior of the heat-treated WC-12Co coatings

WC-Co coatings were produced on SS 410 plates and subjected to heat treatment at different temperatures (from 300 to 900 °C). The microstructural studies and structural analysis of the coatings before and after heat treatment were carried out by electron microscopy and X-ray diffraction analysis. From the Vickers indentation method, hardness values were measured, and higher microhardness was observed for the coatings after heat treatment. The sample that was heat-treated at 750 °C exhibited the highest hardness. From the sliding wear test results, the wear resistance of the coatings was observed as increased after the heat treatment. However, it was found that the heat-treated coatings at 600 °C exhibited higher wear resistance. Cracking and fracture were the dominant wear mechanisms observed for the heat-treated coatings, along with coating delamination and oxidation.

Investigation of wear and friction characteristic of Al/(Si3N4)np nano composites under as-cast and heat-treated conditions

Several automotive components, such as clutch plate, piston and cylinder liner, etc., require excellent wear characteristics. The current study focused on fabricating nano Si3N4 reinforced Al alloy composites through a stir casting route with ultrasonic assistance, then performing T-6 heat treatment to alter their properties. Dry sliding wear tests were performed to investigate the frictional and wear characteristics at various applied loads and sliding distances. Results reveal that the coarse grain of α-Al was significantly refined after incorporating nano Si3N4 particles in it, and their structure was transformed from coarse columnar to rosette-like dendrites. The hardness and wear resistance increase with nano Si3N4 addition and T-6 heat treatment. The formation of SiO2 and Fe2O3 layers at the interacting interface significantly reduces the coefficient of friction of nanocomposites. The volumetric loss increased with load (15 N to 45 N) and sliding distance (500 m to 3000 m) for cast and heat-treated samples. The maximum volumetric loss was found in the case of as-cast alloy and the minimum for heat-treated Al/2wt.% Si3N4 nanocomposites. The SEM investigation of worn surfaces shows that the adhesive mechanism is more dominant in alloys, whereas the abrasive wear mechanism was associated with nanocomposites.

Evaluation of mechanical and wear properties of AA6063/(Si3N4)6%–12% /(CuN2O6)2%–4% composite via PM route and optimization through robust design technique

The study is to investigate the physical, mechanical, and tribological properties of Al6063 alloy reinforced by Silicon Nitride (Si3N4) & compound Copper Nitrate (CuN2O6) processed via Powder Metallurgy (PM) Techniques. Incorporation of reinforcement in matrix material ranged from 6 to 12% Si3N4 in a 6-step interval, and 2 to 6%CuN2O6 in a two-step interval. The characterizations were made on the PM produced specimens using OM, EDS, XRD and hardness. The reinforcement particles were distributed uniformly is attributed by homogeneous mixer of matrix and reinforcements. The tests were carried out in accordance with ASTM Standards on the Al6063 alloy and its composites. The test findings show that as the reinforcing percentage of ceramic and inorganic compound is increased, properties such as hardness and density rise monolithically and considerably. The dispersion of Si3N4 and CuN2O6 reinforcement in the AA6061 matrix was ensured by x-ray diffraction patterns. In comparison to the base alloy, the hardness of AA6063/12%Si3N4/6% CuN2O6 improved by 88% due to the mismatch of thermal expansion between the Al matrix and reinforcement causes huge internal stress, causing the aluminium matrix to deform plastically to lodge the smaller volume expansion of Si3N4 and CuN2O6 particles. The dry sliding wear test was carried out on a tribometer with a pin-on-disc arrangement, and the findings show that the composite has a higher wear resistance. The Taguchi design of experiments was used to investigate the solution containing parameters employing an orthogonal array, the signal-to-noise ratio, and analysis of variance. The weight percentage of Si3N4/CuN2O6 compound and the relationship between wt% of reinforcement and applied load had the highest impact on composite wear resistance, accounted for 31.66%. Before and after the wear morphology during the wear test, images from a scanning electron microscope and energy dispersive microscopy were used to examine the manufactured composites.

Physical, mechanical, and sliding wear behavior of epoxy composites filled with surface modified walnut shell particulate

AbstractThe current study aims to examine the influence of surface‐modified micro‐sized walnut shell particulates (WSP) with an aqueous solution of sodium hydroxide (NaOH) on epoxy composites. For that, epoxy/WSP composites are prepared by varying the WSP content up to 20 wt%. In this investigation, the physical properties (surface morphology, density, voids percentage, water uptake), mechanical properties (tensile, flexural, compressive, hardness), and sliding wear behavior of the composites are reported. From the micrographs, it is clear that WSP established good adhesion with the epoxy matrix. Further, it is found that the density, void content, water intake capacity, compressive strength, and hardness increase with WSP loading. Against that, the tensile and flexural strength is somewhat reduced at higher filler loading. Sliding wear tests are performed as per L25 Taguchi's orthogonal array. From the analysis, it is observed that WSP content is the most significant factor and sliding distance is the least significant factor for minimizing the wear rate. For analyzing the sliding wear performance under varied conditions, a prediction model is proposed using an artificial neural network to forecast the sliding wear rate of epoxy/WSP composites over a wide range of experimental domains.

Effect of the reduced graphene oxide on the tribological behavior of UHMWPE/rGO nanocomposites under sliding contact conditions

AbstractIn this work, the effect of the addition of reduced graphene oxide (rGO) nanofillers to UHMWPE was investigated. The UHMWPE/rGO nanocomposites were prepared at rGO contents of 0.010, 0.10, 0.25, and 0.50 wt%. The morphological, mechanical, and surface properties of the nanocomposites and the neat UHMWPE were evaluated and related with their tribological behavior. For that, DSC, SEM, contact angle, MO, and profilometry techniques, besides shore D hardness tests, instrumented indentation tests and pin‐on‐disc sliding wear tests were performed. The results showed that nanocomposites with rGO contents of 0.10 and 0.25 wt% exhibited higher crystallinity degree than the neat UHMWPE, which improved significantly their mechanical and tribological behavior through increases of around 40% in the instrumented hardness and the elastic modulus, and a significant reduction of up to 48% in the coefficient of friction when compared to the neat UHMWPE. Additionally, the presence of rGO decreased the work of adhesion of the nanocomposites/counterface pairs, resulting in friction and wear mechanisms changes in comparison with the neat polymer.

Tribological performances of α-Zrp as the additive of the grease used for mine hoisting wire rope

Considering that the lubrication failure of the wire rope in mine hoisting is easy to occur under harsh conditions, which will accelerate the wear of the wire rope and seriously threaten the safety of hoisting. Therefore, the anti-wear characteristics of α-type zirconium hydrogen phosphate (α-ZrP) on the wire rope grease used for mine hoisting were studied. First, the modified greases with different mass fractions of α-ZrP were prepared, and then the dispersion of α-ZrP in the original grease was discussed. Finally, the friction and wear properties of the α-ZrP modified greases were investigated by the four-ball machine, fretting wear test rig of steel wire and sliding wear test rig of wire rope. The results show that the coefficient of friction (CoF) increases first and then decreases with the increase of α-ZrP added in the grease in the four-ball friction test and the sliding wear test of wire rope. In addition, it will agglomerate in the original grease when the addition of α-ZrP is too large, which will worsen the lubrication effect, and the wear mechanism also changes from abrasive wear to abrasive wear and adhesive wear. Moreover, dry friction may occur between steel wires when the additive content is low, thus accelerating their wear. The improvement effect of the original grease is the most significant for the mine hoisting wire rope when the mass fraction of α-ZrP is 2.5% according to the principal component analysis theory.

Influence of boron carbide content on dry sliding wear performances of AZ91D magnesium alloy

In this study, AZ91 magnesium alloy based metal matrix composites are made-up of bottom pouring stir casting with 0 wt.%, 1.5 wt.% and 3 wt.% boron carbide (B4C) particles reinforcements. The influence of hard reinforcements on mechanical properties such as hardness and tensile strength has been investigated for the casted composites samples. It was found that by adding 1.5 wt. % and 3 wt.% B4C particles, the Rockwell hardness value of 3.2% and 4.6%, Ultimate Tensile Strength (UTS) values of 15.5% and 26.3% of the composites increased respectively. The influence of B4C contents on AZ91D mg alloy wear study was carried out using pin on disc apparatus. Also, the effect of applied load (5N, 10N, and 20N) on wear properties was investigated. The results of the dry sliding wear tests show that AZ91D- B4C magnesium composite has less wear loss than the unreinforced AZ91D magnesium alloy. X-ray diffraction (XRD) analysis were performed for finding the various compounds such as MgO, B4C and Mg17Al12 present in the developed composites. Further, scanning electron microscopy (SEM) analysis were performed on the worn-out pin surfaces to investigate the wear pattern. These findings indicate that the addition of B4C content improved mechanical characteristics and wear resistance, which may also be used in the automotive and aerospace industries.

Three-dimensional finite element simulation and experimental validation of sliding wear

Wear tests involving thousands of operating cycles can be impractical and costly. Therefore, the use of numerical methods to predict surface evolution due to wear can be a good alternative. A generalised three-dimensional finite element (FE) method is presented here to determine the wear of mechanical components. The method is tested and validated against the results obtained from the ball on disc sliding tests performed on different materials and in different conditions, with the aim to predict the wear profiles of the ball and disc. The wear simulation procedure is, for simplicity, based on Archard’s wear law and is implemented in a commercial FE package, ABAQUS. The developed methods are appropriate for 3D surfaces and the wear profiles are based on the accurate determination of the contact pressure. The surface evolutions of both contacting bodies are calculated simultaneously. The generation of artificial roughening of the worn surfaces due to numerical restrictions of element sizes is minimised using a local smoothening procedure. The developed methods are compared with the results obtained for reciprocating sliding tests, which result in wear of few microns wear depths, and continuous sliding tests, which result in tens of microns wear depths. The results were generally in good agreement with the test, with the maximum discrepancy of ∼ 10% in all indicators used, considering the statistical error margin of the tests. The developed method is versatile and applicable to a wide range of sliding wear tests. The model can be updated to consider both more complex material descriptions and to incorporate tribofilm or oxide layer growth or removal.

Physical, mechanical, and sliding wear behavior of micro‐sized Linz‐Donawintz slag filled epoxy composites

AbstractLinz‐Donawintz (LD) slag is a solid waste produced during the basic oxygen furnace process of steel making and is more often disposed of on nearby land causing a disturbance in vegetation and human health. Hence, judicial management of LD slag is a need for an hour. For this purpose, the usability of LD slags as a reinforcement material in epoxy composites was investigated in the present work. In this investigation, the physical properties (density, void content, water absorption rate), mechanical properties (tensile properties, flexural properties, compressive strength, hardness), and tribological properties (sliding wear behavior) are reported. From the experimental investigation, it is found that the density, void content, and water intake capacity increase with LD slag loading. The maximum voids present in the composite is 1.92% for epoxy/40 wt. % LD slag composite. Similarly, maximum water uptake of only 0.6% is observed for composite with maximum filler content and for maximum immersion time. Further, it is observed that the strength of composite under tensile and flexural loading was compromised slightly. At 40 wt. % of LD slag, the measured tensile and flexural strength are 20.8 MPa and 28.78 MPa respectively. The strength of composites under compressive loading increases with filler content and reaches a maximum of 108 MPa for epoxy/40 wt. % LD slag composite. The high hardness of filler assists in increasing the hardness of the composites. The hardness of neat epoxy is Shore‐D number 75 which increases to Shore‐D number 84. With increased hardness, ultimately the specific wear rate under dry sliding conditions reduces. Taguchi's L25 orthogonal array having four factors, each at five different levels is implemented to conduct the sliding wear tests. A forecast model is built on an artificial neural network (ANN) which successfully envisages the sliding wear performance of the composite under investigation inside and outside the experimental domain.

Formation mechanism and wear behavior of gradient nanostructured Inconel 625 alloy

The formation mechanism and wear behavior of a gradient nanostructured (GNS) Inconel 625 alloy were investigated using SEM, TEM and ball-on-disc sliding wear tester. The results show that surface mechanical grinding treatment (SMGT) induced an approximately 800 μm-deep gradient microstructure, consisting of surface nano-grained, nano-laminated, nano-twined, and severely deformed layers, which resulted in a reduced gradient in micro-hardness from 6.95 GPa (topmost surface) to 2.77 GPa (coarse-grained matrix). The nano-grained layer resulted from the formation of high-density nano-twins and subsequent interaction between nano-twins and dislocations. The width and depth of the wear scar, wear loss volume, and wear rate of the SMGT-treated sample were smaller than those of untreated coarse-grained sample. Moreover, the wear mechanisms for both samples were mainly abrasive wear and adhesive wear, accompanied with mild oxidation wear. The notable wear resistance enhancement of the GNS Inconel 625 alloy was attributed to the high micro-hardness, high residual compressive stress, and high strain capacity of the GNS surface layer.

A novel approach for evaluation of load bearing capacity of duplex coatings on aluminum alloy using PLS and SVR models

Duplex NiP/TiN coatings consisting of the electroless intermediate layers and the physical vapor deposition (PVD) top layers were fabricated on the AA6061 aluminum alloy in order to enhance the load bearing capacity. The main objective of this study was to model the load bearing based on the thickness, adhesion and elastic modulus of the coatings. For this purpose, partial least square (PLS) and support vector regression (SVR) approaches were employed. The results showed that both models had an acceptable performance; however, the PLS model outperformed SVR. The correlation coefficients between thickness, adhesion and elastic modulus with load bearing were 0.841, 0.8092 and 0.7657, respectively; so, thickness had the greatest effect on the load bearing capacity. The composition and structure of the samples were evaluated using XRD and SEM. The load capacity of the coated samples was also discussed based on the wear and adhesion evaluations. Dry sliding wear tests, under a load of 2 N and a sliding distance of 100 m, demonstrated the complete destruction of the coated specimens with low load capacity. The samples with high load capacity showed not only a superior tribological performance, but also a remarkable adhesion according to the Rockwell superficial hardness test.

A study of processing and parametric optimization of wear-resistant AZ91-TiB2 composite fabricated by ultrasonic-assisted stir casting process

In the present research, a lightweight and wear-resistant TiB2 reinforced AZ91D Mg metal matrix composite was developed using an ultrasonic-assisted stir casting process for aerospace and automobile applications. Stirrer speed, ultrasonic power, and TiB2 reinforcement concentration were considered the input process parameters, which were optimized with the help of Taguchi’s L9 orthogonal array, followed by grey relational analysis to develop the composite with high hardness and wear resistance. Pin-on-disc sliding wear testing was conducted to evaluate the wear resistance of the composites fabricated at different process parameter settings. SEM, EDS, and XRD examined the microstructure, wear mechanisms, elemental composition, and different phases in the developed composites. The microhardness of the specimens was determined using a Vickers microhardness tester. The results revealed that the process parameter setting with a stirrer speed of 400 rpm, 1500 W of ultrasonic power, and 3 wt% of TiB2 reinforcement concentration had the highest grey relational grade, which resulted in the development of a composite material exhibiting the high microhardness and minimum wear. The microstructural investigation revealed that the ultrasonic agitation of the liquid melt resulted in nearly uniform dispersion of the TiB2 reinforcement particulates in the composite. During the sliding wear test, the material removal in the composite specimens occurred due to the adhesion, oxidation, delamination, pull-out of reinforcement particles, and eruption of the Mg alloy matrix.

Dry sliding wear behaviour of metal toughened nanoceramics: A case study of aluminium-alumina nanocermets

Sliding wear experiments were performed on the set of six Al–Al2O3 nanocermets, which were optimally designed with a tuned volumetric concentration of 20% Al and 80% Al2O3 to achieve a tailored cocooning of Al2O3 particles with thin Al film in the cermet structure. A combination of cryo-milling and room temperature-ball milling was carried out to prepare Al0.2-(Al2O3)0.8 powder mixtures and the nanocermets were prepared by spark plasma sintering (SPS). Pure Al, Al2O3 and nanocermet samples were subjected to a dry sliding wear test against a steel counter-body with the contact diameter of 1 mm to estimate their relative wear behaviour. The results suggest that the wear behaviour of nanocermets is comprised of both abrasive and adhesive losses. An increase in the milling duration of powder mixtures improved the wear resistance of the sintered nanocermets. Abrasion, adhesion, fracture, delamination and ploughing were found to be the major material removal mechanisms from the wear tracks. SEM was utilized to understand the morphological features of the wear tracks and wear debris, while XRD was used for the phase evaluation of the samples. HRTEM was used to observe the distribution of phases in the sintered nanocermet structure.

Microstructural, Mechanical and Wear Properties of Al–1.3%Si Alloy as Compared to Hypo/Hyper–Eutectic Compositions in Al–Si Alloy System

The microstructure, mechanical properties, and wear behavior of three Al–Si alloys, namely: Al–1.3%Si, Al–1.5%Si and Al–13.5%Si were investigated. The specimens were examined by using an optical microscope to investigate the microstructural features of pin materials. Microhardness numbers and mechanical behavior parameters were determined by using a microhardness indenter and compression test, respectively. The dry sliding wear test was carried out using a pin-on-disc apparatus by varying the rotational speed (250, 350, and 450 rpm), normal load (5, 10 and 20 N) and test time (5, 10 and 15 min) at a constant sliding diameter of 300 mm. The surface roughness index (Ra) of the worn surfaces was determined by using a profilometer. The microstructure of Al–1.3%Si alloy was described as a fine eutectic colonizing in the FCC-Al phase matrix. Coarse eutectic dendrites surrounding the primary FCC-Al grains were observed in Al–1.5%Si alloy. The microstructure of Al–13.5%Si alloy showed a uniform layered structure of FCC-Al + Diamond Si eutectic. The average microhardness number was directly proportional to the Si concentration. Al–13.5%Si alloy with a high microhardness number (47.16 HV) showed excellent resistance to wear and exhibited a smoother surface at the end-of-wear test. The improved wear resistance in this case could be due to the presence of Diamond-Si hard phase in large quantities compared with other compositions. On the other hand, Al–1.5%Si alloy showed poorer resistance to wear because the mass loss action was dominated by a particle detachment mechanism. The response surfaces of the mass loss vs. speed, normal load and time showed increased mass loss when the three controlled parameters were increased. However, Pareto charts of the main effects of parametric interactions showed that the normal load was the main factor that must be considered when studying the tribological properties of Al–Si alloys.