Dry Sliding Wear Conditions Research Articles

Wear characteristics of hybrid aluminum-matrix composites reinforced with well-dispersed reduced graphene oxide nanosheets and silicon carbide particulates

In the present study, hybrid composites consisting of a hypoeutectic aluminum-silicon (Al-Si) matrix with silicon carbide (SiCp) (10 wt%) and various reduced graphene oxide (RGO) (0.3–0.7 wt%) contents were fabricated using a combined solution-mixing and powder metallurgy (PM) route. The tribological behaviors of these composites against a GCr15 steel ball were studied under dry sliding-wear conditions using a ball-on-disc configuration. The effects of the RGO content and applied loads on the coefficient of friction (COF) and wear rates were evaluated. To study the wear mechanism, comprehensive characterization of the worn surfaces and debris was performed using scanning electron microscopy (SEM). In contrast with the Al-Si/SiCp composite, the hybrid Al-Si/SiCp/RGO composites showed reduced wear rates because of the stabilized COF, and the self-lubricating effects of the incorporated RGO. In the case of all the composites, the wear rate increased as the load increased. Delamination wear is the dominant wear mechanism of the Al-Si/SiCp composite, at both low and high loads. At low loads, the dominant wear mechanism of the Al-Si/SiCp/RGO hybrid composites is abrasive wear accompanied by adhesion wear; this transitions to delamination wear at high loads.

Microstructure and Wear Performance of ECAP Processed Cast Al–Zn–Mg Alloys

In the present investigation, wear performance of equal channel angular pressing (ECAP) processed cast Al–Zn–Mg alloys under dry sliding wear conditions was studied against a steel disc. Initially, Al–Zn–Mg alloys (with 5, 10, 15% zinc and 2% magnesium) were ECAP processed. After ECAP, grain size was reduced and enhancement in the hardness was observed. Wear resistance of the alloys increased after ECAP processing. Wear resistance of the alloys also increased when the quantity of the zinc was increased in the alloys. But, wear resistance of all three alloys decreased with increase in the load and the sliding speed. Coefficient of friction of the alloys decreased after ECAP processing. Coefficient of friction of the alloys also decreased when the quantity of the zinc was increased in the alloys. Coefficient of friction of all three alloys increased with increase in the load and the sliding speed. Irrespective of the alloy composition and applied load, worn surfaces of the cast and homogenized samples were composed of plastic deformation, scratches and micro-ploughing. On the other hand, in ECAP processed samples, morphology of the worn surfaces depended on the applied load. Abrasive wear is the main wear mechanism perceived in cast and homogenized samples at all loads. While in ECAP processed samples, the wear mechanism shifted from adhesive and oxidation wear to abrasive wear with increase in the load. Formation of oxide layers on the surface of the sample increased with increase in the ECAP passes. In ECAP processed samples, transfer of iron content from the disc to the sample surface was identified.

Experimental investigation of dry sliding wear behaviour of jute/epoxy and jute/glass/epoxy hybrids using Taguchi approach

Natural fibre reinforced polymer composites are being used as replacement to conventional non-renewable reinforcing materials due to its significant properties such as light weight, competitive strength and low cost. It has gathered attention in many industries such as automotive and construction. Among all natural fibres, jute fibres possess good properties, low cost and easy commercial availabilities. The behaviour of jute/epoxy and jute/glass/epoxy composites was examined under dry sliding wear condition. The wear test was performed on pin-on-disc wear test machine and results were further analyzed using Taguchi technique. Effect on wear performance of composite plates were investigated for different sliding velocities (1m/s, 2m/s and 3m/s), applied loads (10N, 20N and 30N) and sliding distances (1000m, 1500m and 2000m). The analysis of variance was carried out to study the relative significance of individual factor on wear characteristics. Linear regression analysis was used to obtain an empirical relation between operating parameters and wear rate. Experimental results showed that, hybridization of jute epoxy with glass fibre shows better resistance to wear. It was also observed that the applied load was more influencing parameters on tribological performance of composites.

Modelling and Characterisation of Electrical Discharge TiC-Fe Cermet Coatings

The creation of coatings via Electrical Discharge (ED) methods can enhance the functionality of components which are subject to prior ED machining process steps. However, the industrial application of these methods has been limited due to poor understanding of the fundamental interaction between energy source and material. In this paper, for the case of a TiC sacrificial electrode deposited onto a stainless steel, 2D transient heat transfer is modelled and solved by a finite difference method to estimate the effective fraction of total energy transferred to the workpiece, as well as heat distribution and expected microstructure upon ED coating (EDC). The model was validated via comparison with experimental data, as well as data in literature. In addition, a TiC coating was tested under dry sliding wear conditions to evaluate its tribological properties against an Al2O3 counter face sphere using ball-on-flat geometry. The effective amount of energy transferred to the workpiece is predicted to vary between 17% and 23% for increasing current, from 2 to 19 A, at fixed pulse-on time of 8μs; and between 7% and 53% for increasing pulse-on time, from 2 to 64μs, at fixed current of 10 A. Backscattered electron (BSE) imaging showed that the coatings comprised a metal matrix composite, with a complex banded fine-grained microstructure and different cooling rate across the coating. A TiC-based ED coating on 304 stainless steel (304-SS) yielded a wear rate two orders of magnitude lower than that of the substrate only.

Optimization of hybrid aluminum composites wear using Taguchi method and artificial neural network

PurposeThis research aims to describe the influence of weight per cent of graphite (Gr), applied load and sliding speed on the wear behavior of aluminum (Al) alloy A356 reinforced with silicon carbide (SiC) (10 Wt.%) and Gr (1 Wt.% and 5 Wt.%) particles. The objective is to analyze the effect of the aforementioned parameters on a specific wear rate.Design/methodology/approachThese hybrid composites are obtained by means of the compo-casting process. Tribological analyses were conducted on block-on-disc tribometer at three different loads (10, 20 and 30 N) and three different sliding speeds (0.25, 0.5 and 1 m/s), at the sliding distance of 900 m, in dry sliding wear conditions. Optimization of the tribological behavior was conducted via the Taguchi method, and ANOVA was used for the analysis of the specific wear rate. Confirmation tests are used to foresee and check the experimental results. Examined samples were analyzed via a scanning electron microscope (SEM). Regression models for predicting specific wear rate were developed with Taguchi and ANN (artificial neural network) methods.FindingsThe biggest impact on value of specific wear rate has the load (43.006%), while the impact of Wt.% Gr (31.514%) was less. After comparison of the results, i.e. regression models, for predicting the specific wear rate, it was observed that ANN was more efficient than the Taguchi method. The specific wear rate of Al alloy A356 with SiC (10 Wt.%) and Gr (1 Wt.% and 5 Wt.%) decreases with a decrease in the load and weight per cent of Gr-reinforcing material, as well as with a decrease in sliding speed.Originality/valueThe results obtained in this paper using the Taguchi method and the ANN method are useful for improving and further investigating the wear behavior of the SiC- and Gr-reinforced Al alloy A356.

Effect of Laser Power on Metallurgical, Mechanical and Tribological Characteristics of Hardfaced Surfaces of Nickel-Based Alloy

In this present work, nickel based alloy was deposited on 316 LN austenitic stainless steel (ASS) by a laser hardfacing technique to investigate the influence of laser power on macrostructure, microstructure, microhardness, dilution and wear characteristics. The laser power varied from 1.1 to 1.9 kW. The phase constitution, microstructure and microhardness were examined by optical microscope, scanning electron microscopy, energy dispersion spectroscopy and Vickers microhardness tester. The wear characteristics of the hardfaced surfaces and substrate were evaluated at room temperature (RT) under dry sliding wear condition (pin-on-disc). The outcome demonstrates that as the laser power increases, dilution increases and hardness of the deposit decreases. This is because excess heat melts more volume of substrate material and increases the dilution; subsequently it decreases the hardness of the deposit. The microstructure of the deposit is characterized by Ni-rich carbide, boride and silicide.

On surface modification of austenitic stainless steel using microwave processed Ni/Cr3C2 composite cladding

ABSTRACTIn the present work Ni-based + 20% Cr3C2 composite clads were developed on SS-304 austenitic stainless steel through microwave hybrid heating technique. Experimental trials were conducted inside a domestic microwave applicator at 2.45 GHz and 900 W. The developed microwave composite clads were characterised through SEM/EDS, XRD and Vicker’s micro-hardness tests. Further tribological wear behavior of the so developed clad was investigated using pin-on-disc type tribometer under dry sliding wear conditions. Microstructural analysis revealed the uniform dispersion of Cr3C2 particles inside the Ni matrix in the form of cellular-like structure. The presence of FeNi3, NiSi, Cr3Ni2 and chromium carbide (Cr3C2) was confirmed from the XRD analysis, which contributes to the increase in micro-hardness of the composite clad. The average value of micro-hardness of the developed clads was found to be 450 ± 55 HV. The microwave-processed clad exhibits three times more wear resistance than SS-304 substrate.

Experimental Study on Frictional Characteristics of Scapharca Broughtonii under Dry Sliding Wear Conditions

In this paper, the friction and wear properties of Scapharca broughtonii were investigated under low-speed (5-45 mm/s) and low-load (1.5N-6N) conditions by using a micro-tribological tester. The stereoscopic microscope and computer imaging analysis system was employed to test the abrasion slide size and calculate the wear volume of Scapharca broughtonii. The worn surface morphology of Scapharca broughtonii was observed by a scanning electron microscope (SEM), and the wear mechanism of Scapharca broughtonii was obtained. Experimental results show that the friction coefficient decreased rapidly with an increase in sliding speed under low-load and low-speed dry sliding conditions. When the load was below 6N, the influence of microstructure on the friction coefficient was very small. The wear rate of Scapharca broughtonii increased with an increase in sliding speed when the load was greater than 6N. When the speed increased, the influence of load on the friction coefficient occupied a dominant position. At the same time, the wear rate was increased with an increase in load. The main wear mechanisms of Scapharca broughtonii were stress fatigue wear and three-body abrasive wear, and mild adhesive wear and abrasion.

Influence of Parameters and Wear Analysis of Aluminium-Bronze (CuAl8Fe3) by Taguchi Method

Objective: The tribiological activity of aluminium bronze (CuAl 8 Fe 3 ) has been explored using the pin-on-discmachine at various loads under dry sliding wear condition. Method/Analysis: The work piece had a size of 11.4mm in Diameter, 103 mm in length. In this paper, the wear rate has been evaluated at loads (1, 2 and 3 Kg) and Disc speed (500, 700, 900 rpm) at different time intervals. Taguchi method is applied to find out the powerfullness of parameters and optimization of influence of wear rate factors like speed, load and time on dry sliding wear. Findings:The results proves that the applied load was the major parameter among the controllable factors that cause the weight loss of aluminium bronze (CuAl 8 Fe 3 ). For aluminium bronze(CuAl 8 Fe 3 ), the load had the greatest effect on the wear. The sliding speed had a minimum effect. The best combination of the testing parameters could be determined. A good agreement is found between the forecasted and actual weight loss. Application/Improvement: The most influencing parameters involved tribiological industries are speed, load, time and indirectly sliding velocity were considered throughout the theoretical investigation.

Effect of WS2 Addition on Tribological Behavior of Aluminum at Room and Elevated Temperatures

The objective of this study is to evaluate the role of WS2-based two-dimensional material as solid lubricant additive to aluminum to reduce the friction. Al-2 vol% WS2 was consolidated by spark plasma sintering into a 99% dense composite. Tribological behavior of Al-2 vol% WS2 and pure Al was evaluated at room temperature and 200 °C using the ball-on-disk method in dry sliding wear conditions. Wear mechanism was studied using wear surface and sub-surface via electron microscopy and focused ion beam milling. Al-2 vol% WS2 showed the lowest coefficient of friction value of 0.55 at 200 °C as compared to 0.82 that of pure aluminum. The wear rate of Al-2 vol% WS2 showed 54 and 29% improvement at room temperature and 200 °C, respectively, as compared to pure Al. The improved tribological properties of Al-2 vol% WS2 are attributed to a tribofilm formation due to the breaking of the weak Van der Waals forces that hold the S–W–S structure. Due to shear forces, a portion of the tribofilm is transferred on the counter surface providing lubrication properties resulting in a stable and low COF.

Microstructural evolution of die-cast and homogenized AZ91 Mg-alloys during dry sliding condition

Abstract Microstructural evolution of die-cast and homogenized AZ91 Mg-alloys was investigated during dry sliding wear condition. Tribological tests were performed using a pin-on-disc (EN8 steel) configuration with a normal load of 50 N at a constant sliding speed of 2.5 ms −1 under ambient environment. Delamination was recognized as a predominant wear mechanism in both of these materials. The die-cast AZ91 Mg-alloy exhibits lower coefficient of friction and higher wear rate. This can be ascribed to increase in the intensity of load bearing capacity of hard β-Mg 17 Al 12 phase, and crack formation/de-cohesion at the interface between primary α-Mg and discontinuous β-Mg 17 Al 12 phases. On the contrary, the homogenized AZ91 Mg-alloy experiences higher coefficient of friction and lower wear rate. The friction-induced microstructural evolution (supersaturated α-Mg to eutectic (α + β-Mg 17 Al 12 )) tending to minimize the wear rate by providing barrier to material removal in the near surface region of homogenized AZ91 Mg-alloy. Therefore, experimental observation revealed that an inverse relationship exists between wear rate and coefficient of friction for the investigated materials. The analysis of worn surfaces and subsurfaces by electron microscopy provided evidence to delamination wear and microstructural evolution.

Surface characterization and specific wear rate prediction of r-GO/AZ31 composite under dry sliding wear condition

The effect of reduced graphene oxide (r-GO) nanosheets on the dry sliding wear behaviour of AZ31 alloy composites produced by solvent based powder metallurgy technique has been investigated. The percentage of reinforcement addition was limited to 0.2% and 0.4%. Results show that r-GO nano-sheets considerably increases the microhardness upto 64.4 HV. The tribological behaviour of composites was investigated by pin on disc tribometer for an optimal set of control factors. Reinforcement weight percentage, load, sliding distance and sliding velocity was taken as input parameters. Taguchi coupled artificial neural network has been used to plan and analyze the experiment. Based on the study it was observed that reinforcement weight percentage and load are the most influencing factor which affects the specific wear rate. Adapted ANN results show better predictablity with R-value 99.98% and the same was effectively used to investigate the behaviour of each control factors.

Influences of extrusion temperatures on the wear behavior of magnesium alloy AZ31 fabricated by the extrusion shear process

Abstract The wear resistance of as-cast AZ31 magnesium alloy samples fabricated by extrusion shear (ES) with various preheating temperatures (420, 400, 370 °C) of billets was tested by using pin-on-disc experiments under dry sliding wear conditions. Wear rates and friction coefficient were measured at various sliding frequencies and normal forces. To define the wear mechanism for each tested condition, the worn surfaces were analyzed using scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDS). Based on the test results, the wear resistance of the ES-processed samples decreases with drop of the billet temperatures. The friction coefficients and wear rates of the samples with a preheating temperature of 370 °C are lower than those with deformation temperatures of 400 °C and 420 °C. With the increase of normal loads and reciprocating frequencies, the wear mechanism changes from mild wear (adhesion, abrasion and oxidation) to severe wear (delamination, plastic deformation and melting). Therefore, the extrusion methods have significant influences on the wear behaviors of the samples, and the wear resistance of AZ31 magnesium alloy can be improved by ES process.

Surface modifications of an aluminum-magnesium alloy through reactive stir friction processing with titanium oxide nanoparticles for enhanced sliding wear resistance

Reactive friction stir processing (RFSP) has been employed to modify the surface properties of AA5052 Al-Mg alloy through grain refinement and the distribution of ultrafine hard nanoparticles (2 to 6% volume fractions of 50nm titanium dioxide). The heat generated induced solid state reactions between the metal matrix and the reinforcement to form Al3Ti/MgO inclusions. The role of grain refinement and distributed hard nanoparticles on the tribological behavior of the alloy under dry sliding wear condition was evaluated. The wear rates and friction coefficient as well as macro- and micro-features of the worn surfaces indicate that the wear mechanism (at 3–7kgf and 0.5m/s) is abrasive. The wear rate decreased with increasing volume fraction of the hard inclusions with a significant reduction in the friction coefficient. The wear resistance could be improved >125% (compared with the annealed alloy) at 6vol% TiO2. The relations between the enhanced wear resistances, the microstructural changes and mechanical properties have been characterized.

Surface characteristics and wear depth profile of the TiN, TiAlN and AlCrN coated stainless steel in dry sliding wear condition

Titanium nitride (TiN), titanium aluminum nitride (TiAlN), aluminum chromium nitride (AlCrN) are hard ceramic coating material. It is coated over stainless steel (SS304) and sliding against Ti–6Al–4V alloy by using cathodic arc deposition (CAD) method, the mechanical and wear properties are improved significantly. The surface hardness, roughness and wear rate for the three coated samples are studied and compared. The wear test is carried out by using the ball-on-disc with changing the tribological parameters of the applied load (3–6N), sliding velocity (0.32–0.75m/s) and sliding distance (580–1500m). It is concluded that the TiN coating on the SS304 surface offers good mechanical and tribological properties when compared to the other coatings. 3D surface profile graphs are used effectively to study the wear depth and wear surface behavior of the coated sample.

Suspension High Velocity Oxy-Fuel (SHVOF)-Sprayed Alumina Coatings: Microstructure, Nanoindentation and Wear

Suspension high velocity oxy-fuel spraying can be used to produce thermally sprayed coatings from powdered feedstocks too small to be processed by mechanical feeders, allowing formation of nanostructured coatings with improved density and mechanical properties. Here, alumina coatings were produced from submicron-sized feedstock in aqueous suspension, using two flame combustion parameters yielding contrasting microstructures. Both coatings were tested in dry sliding wear conditions with an alumina counterbody. The coating processed with high combustion power of 101 kW contained 74 wt.% amorphous phase and 26 wt.% crystalline phase (95 wt.% gamma and 3 wt.% alpha alumina), while the 72-kW coating contained lower 58 wt.% amorphous phase and 42 wt.% crystalline phases (73 wt.% was alpha and 26 wt.% gamma). The 101-kW coating had a dry sliding specific wear rate between 4 and 4.5 × 10−5 mm3/Nm, 2 orders of magnitude higher than the 72-kW coating wear rate of 2-4.2 × 10−7 mm3/Nm. A severe wear regime dominated by brittle fracture and grain pullout of the coating was responsible for the wear of the 101-kW coating, explained by mean fracture toughness three times lower than the 72-kW coating, owing to the almost complete absence of alpha alumina.

Mechanical and tribological properties of AA7075–TiC metal matrix composites under heat treated (T6) and cast conditions

The sliding friction and wear behavior of aluminum matrix composites (AA7075–TiC) have been investigated under dry sliding wear conditions. The aluminum metal matrix composites (AMMCs) are produced as AA7075 matrix metal and TiC particulates of an average size of 2μm as reinforced particles through stir casting. AMMCs studied are contained 2–10wt.% of TiC particles in both as cast and heat treated (T6) conditions. All the composites exhibited better mechanical properties (hardness, tensile strength and percentage of elongation) than the matrix metal in both the conditions. The wear tests were carried out at a sliding velocity of 2m/s, sliding distance 2km and at normal load of 20N. The wear resistance of the composites increased with increasing weight percentage of TiC particles, and also the wear rate was notably less for the composite material compared to the matrix material. A detailed analysis in as-cast condition and T6 condition of the AMMCs was carried out using SEM in order to find out the influence of TiC particles in the AMMCs formed. It has been observed that under T6 heat treatment condition, matrix as well as composite shown significant improvement in mechanical and tribological properties when compared in as cast condition.

Controllable two-scale network architecture and enhanced mechanical properties of (Ti5Si3+TiBw)/Ti6Al4V composites.

Novel Ti6Al4V alloy matrix composites with a controllable two-scale network architecture were successfully fabricated by reaction hot pressing (RHP). TiB whiskers (TiBw) were in-situ synthesized around the Ti6Al4V matrix particles, and formed the first-scale network structure (FSNS). Ti5Si3 needles (Ti5Si3) precipitated in the β phase around the equiaxed α phase, and formed the secondary-scale network structure (SSNS). This resulted in increased deformation compatibility accompanied with enhanced mechanical properties. Apart from the reinforcement distribution and the volume fraction, the ratio between Ti5Si3 and TiBw fraction were controlled. The prepared (Ti5Si3 + TiBw)/Ti6Al4V composites showed higher tensile strength and ductility than the composites with a one-scale microstructure, and superior wear resistance over the Ti6Al4V alloy under dry sliding wear conditions at room temperature.

Wear study of Mg-SiCp reinforcement aluminium metal matrix composite

Lightweight aluminium metal matrix composite materials hold potential requisite for modern tribological applications due to its inherent and better wear resistant properties over monolithic metallic materials. This study emphasised on the development of Al based metal matrix composite with SiCp as a reinforcement and magnesium (Mg) as a wetting agent using hybrid stir casting process. The study further analysed the effects of different size variations of silicon carbide particles such as the coarse particle size, fine particle size, intermediate particle size and mixed particle size in the fabrication of the composites on the hardness and wear properties. The pin-on-disc test was also done at room temperature in a dry sliding wear condition. It was observed that the mixed particle size SiCp in composite exhibited superior hardness with the value of 98.2 compared to other particle sizes of SiCp. This is due to the fact that mixed particle size supports a greater fraction of applied load while the fine and intermediate particle sizes sustain the hardening due to dislocation. The multiple particle size reinforced composite exhibits better performance than the single particle size in terms of wear resistance as the wear rate was the lowest with the value of 0.99 X 10-5. It can be concluded that the Mg addition in the composite showed better and tailored properties with a mixed particle size of SiCp of aluminium metal matrix composite.

Effects of fiber surface modification on the friction coefficient of luffa fiber/polyester composites under dry sliding condition

Abstract In this study, the fiber extracted from the fruit of a luffa plant was used as a reinforcement to an unsaturated polyester resin matrix under two different fiber conditions. The untreated and alkali-treated fibers were impregnated and pressed to produce laminates. Composites were made with an optimal compression pressure of 5 MPa for 12 h of curing at room temperature. Ejected samples were cut according to the dimensions specified by the ASTM test specifications. To investigate the effects of fiber surface treatment on the frictional behavior of the produced composites under dry sliding wear conditions, wear test was conducted in a pin-on-disc equipment as per ASTM G99 at varying sliding velocities. In addition, hardness and un-notched impact strengths were measured and discussed. Results showed that the change in fiber surface morphology significantly changed the coefficient of friction of the composites. Moreover, the sliding distance had a prominent influence in increasing the friction between the composite and the counter face.