Tribological behaviour of aluminium alloy (Al-Si10Mg) reinforced with alumina (9%) and graphite (3%) fabricated by stir casting process was investigated. The wear and frictional properties of the hybrid metal matrix composites was studied by performing dry sliding wear test using a pin-on-disc wear tester. Experiments were conducted based on the plan of experiments generated through Taguchi's technique. A L 27 Orthogonal array was selected for analysis of the data. Investigation to find the influence of applied load, sliding speed and sliding distance on wear rate, as well as the coefficient of friction during wearing process was carried out using ANOVA and regression equations for each response were developed. Objective of the model was chosen as 'smaller the better' characteristics to analyse the dry sliding wear resistance. Results show that sliding distance has the highest influence followed by load and sliding speed. Finally, confirmation tests were carried out to verify the experimental results and Scanning Electron Microscopic studies were done on the wear surfaces.

PurposeRecent trends in material science show a considerable interest in the manufacturing of metal matrix composites to meet the stringent demands of lightweight, high strength and corrosion resistance. Aluminium is the popular matrix metal currently in vogue that can be reinforced with ceramic materials such as particulates to meet the desired property. The purpose of this paper is to fabricate hybrid metal matrix composites to improve the dry sliding wear resistance and to study of the effect of sliding speed, load and reinforcement (alumina and graphite) on wear properties, as well as its contact friction.Design/methodology/approachThe present study addresses the dry sliding wear behaviour of Al‐Si10Mg alloy reinforced with 3, 6 and 9 wt% of alumina along with 3 wt% of graphite. Stir casting method was used to fabricate the composites. Mechanical properties such as hardness and tensile strength have been evaluated. A pin‐on‐disc wear test apparatus was used to evaluate the wear rate and coefficient of friction by varying the loads of 20, 30 and 40 N, sliding speeds of 1.5 m/s, 2.5 m/s and 3.5 m/s at a constant sliding distance of 2100 m.FindingsMechanical properties of hybrid metal matrix composites (HMMCs) have shown significant improvement. The wear rate and coefficient of friction for alloy and composites decreased with increase in sliding speed and increased with increase in applied load. Temperature rise during wearing process for monolithic alloy was larger than that of HMMCs and Al/9% Al2O3/3% Gr composite showing the minimum temperature rise.The worn surfaces of the composites were investigated using scanning electron microscope.Practical implicationsThe paper shows that aluminium composites can improve strength and wear resistance.Originality/valueHMMCs has proven to be useful in improving the dry sliding wear resistance.

Purpose – The purpose of this paper is to explore the use of fly ash and graphite particles as low cost reinforcing materials for improved wear resistance, enhanced mechanical properties and reduction in density of hybrid composites. Design/methodology/approach – The AlSi10Mg/fly ash/graphite (Al/FA/Gr) hybrid composite was synthesised by stir casting method. The dry sliding wear and friction behaviour of hybrid composites were studied using pin-on-disc machine by varying parameters like load and weight fraction of fly ash, and compared with the base metal alloy and aluminium-graphite composite. The tests were conducted with a constant sliding speed of 2 m/s and sliding distance of 2,400 m. Findings – The hybrid composites exhibit higher hardness, higher tensile strength and lower density when compared to unreinforced alloy and aluminium-graphite composite. The incorporation of fly ash and graphite particles as reinforcements caused a reduction in the wear rate and coefficient of friction (COF) of the hybrid composites. The improvement in the tribological characteristics occured due to the load carrying capacity of hard fly ash particles and the formation of a lubricating film of graphite between the sliding interfaces. The wear rates and COF of unreinforced aluminium alloy and composites increase with an increase in the applied normal load. The wear rates and COF of hybrid composites decrease with an increase in the fly ash content. 9 wt.% fly ash and 3 wt.% graphite reinforced hybrid composite exhibited the highest wear resistance and lowest COF at all applied loads. Abrasive wear and delamination were dominant in the mild wear regime of aluminium alloy and composites. Due to subsurface deformation and crack propagation, plate-like wear debris were generated during delamination wear. In the severe wear regime, the dominant wear mechanism was adhesive wear with formation of transfer layers. Practical implications – It is expected that these findings will contribute towards the development of lightweight and low cost aluminium products with improved tribological and mechanical properties. Originality/value – The wear and friction data have been made available in this article for the use of Al/FA/Gr hybrid composites in tribological applications.

Medium carbon steel (EN8) substrates with different Surface Roughness (SR) were deposited by Titanium Nitride (TiN). The research work was carried out to investigate the effect of SR and thickness of the thin film coating on substrate structure and tribological properties. EN8 rectangular blocks (60x10x10mm) were used as substrate materials. The variations in SR were achieved by using emery paper on one side and by machining the other side. Scratch tests were conducted and they showed that TiN coatings on substrate with higher SR (1.2 µm) exhibited less adhesion strength compared to TiN coatings on substrate with a lower SR (0.4 µm). Scratch tests also indicated poor adhesion with an increase in the SR of the substrate. The traction force and Coefficient of Friction (COF) were measured during the dry scratch tests under different normal loads, sliding speeds and ramp load conditions. To examine the morphologies of coated substrates and worn surfaces after the scratch test, optical microscopy was utilized. It was found out that TiN coating with a substrate roughness of 0.4 µm exhibited a lower COF and its wear mechanism was adhesive wear. It was experimentally found out that by decreasing the SR of the substrate coatings, wear resistance could be improved.

The aim of the investigation is to study the influence of parameters such as sliding distance, sliding speed, load and fly ash content on dry sliding wear loss and coefficient of friction (COF) of AlSi10Mg-Fly ash-graphite hybrid composites using Taguchi method. A pin-on-disc wear testing equipment was used to conduct the dry sliding wear tests on the hybrid composite produced through the liquid metallurgy route. Signal to noise ratio response analysis and analysis of variance were used to investigate the influence of parameters, and correlation between the parameters was established by multiple linear regression models. It was determined that sliding distance was the most dominant factor influencing the wear and COF of hybrid composites. There was a decrease in wear with increases in sliding speed and fly ash content. However, the COF of composites increased with increasing load, but decreased with increases in sliding distance, sliding speed and fly ash content. At higher sliding speeds, a mechanically mixed layer (MML), containing fractured fly ash particles and oxides of aluminium and iron form between the pin and the counterface. This MML helps to reduce the chance of direct metallic contact, thereby lowering the wear loss and COF. Multiple linear regression models were developed which could be effectively used to predict the wear loss and COF of the hybrid composites. Abrasive wear was the dominant wear mechanism at low loads and when the load was increased to 26?98 N, the wear mechanism changed to mixed abrasion-delamination wear with a drastic increase in the wear loss of the hybrid composite. Mild oxidative wear was predominant at high sliding speeds (3 m s 21 ) and lower loads.