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This work describes the fabrication of a self-lubricating and surface wear-resistant hybrid composite. It has an AZ91D base composite reinforced with a combination of WS2and MoS2particles. The friction stir processing (FSP) technique was utilised to produce all composite specimens by varying the volume fraction to 5%, 10%, and 15%. The samples were prepared, as per the ASTM standards, for conducting various tests to obtain the mechanical properties. The specimens with 15% volume fractions demonstrated the lowest wear rate and the lowest friction coefficient in the wear tests. The sliding speed of 3 m/s and load 30 N results in a lower roughness value of 0.285 μm. The wear mechanisms of the composite were identified from the SEM observations of the worn surfaces of the sample. The load and sliding speed determine what type of wear mechanisms predominate. At lower sliding speeds and loads, abrasion, oxidation, and delamination wear mechanisms were more prominent than adhesion and thermal softening/melting.

The novel friction stir technology is adopted in modern automotive industries to meet the desired properties like hardness, impact toughness and tribological behaviour over the conventional techniques like stir casting, compo casting, squeeze casting, electroplating and infiltration methods. AA7075 surface composites fabricated with different volume fractions of fly ash and emery particles is said to enhance the aforementioned properties. The composites are processed through friction stir process (rotational speed −1200 rpm, transverse speed – 56 mm/min, tool tilt angle – 2 °). During characterization, the Microstructural examination of surface composites depicts fine and homogenous distribution of reinforcements in the friction stir process region owing to severe plastic deformation and dynamic recrystallization process. Substantially, good interface is formed between the reinforcement particulates and base substrate. Inclusion of Fe3O4, Al2O3and SiO2constituents through fly ash and emery reinforcements associated with the homogenous dispersion strengthening mechanism favours for the superior hardness of surface hybrid composite specimen 50E50FA. Decremented grain size and load bearing capacity of the reinforcements is beneficial for the crack propagation resistance that enhances the impact toughness behaviour (17.4 J/cm2) of the same specimen. Wear rate of the specimens are evaluated through pin on disc tribometer. The decrease in the wear rate of hard specimen 50E50FA is observed due to the reduced contact area between its surface and counter disc. The morphology of worn specimens using SEM analysis shows the combined abrasive and adhesive wear as the worn mechanism.

High-temperature wear and friction properties of ZE41 alloy were evaluated using a pin on disc tribometer. The microstructure of the alloy has the equiaxed grains of 72±20µm decorated with the rare earth rich precipitates. Result shows that wear rate decreases upto 100°C and then increases until 250°C for all the loading conditions. The wear mechanism study revealed that the underlying thin oxide tribolayer minimizes the wear rate upto 100°C. Above 100°C, thickening of oxide layer due to enhanced oxidation rate results in breakage of the layer. Further, the increase of temperature softens the alloy which deforms and fractures in the subsurface at low critical load resulting in more delamination wear. The combined effects of oxidation and delamination wear are accentuated with the increase of load and temperature resulting in the increase of the wear rate. Comparing the influence of load and temperature on the wear rate, contact load is more.

Friction stir processing (FSP) has been established as a novel solid state technique to produce bulk and surface metal matrix composites. The present work aim to produce copper matrix composites (CMCs) using FSP and analyze the effect of ceramic reinforcement type (SiC, Al2O3, B4C and TiC) on the evolving microstructure, microhardness and wear resistance behavior. A groove was made on 6mm thick copper plates and packed with various ceramic particles. A single pass FSP was carried out using a tool rotational speed of 1000rpm, travel speed of 40mm/min and an axial force of 10kN. The microstructure and distribution of the ceramic particles were studied using optical and field emission scanning electron microscopy. The sliding wear behavior was evaluated using a pin-on-disk apparatus. The results indicate that the variation in the stir zone, distribution, grain size, hardness and wear resistance of CMCs were within a short range. Nevertheless, Cu/B4C CMC exhibited superior hardness and wear resistance compared to other CMCs produced in this work under the same set of experimental conditions.

The focus on ammonium hydroxide, biodiesels and their combustion technology has garnered significant attention in pursuing carbon-neutral and carbon-free fuels to address greenhouse gas emissions (GHG) and mitigate global warming. Low-temperature combustion (LTC) has been introduced as an alternative method to conventional compression ignition (CI) combustion. Reactivity controlled compression ignition (RCCI) can be achieved by introducing highly reactive waste cooking oil methyl ester (WCOME) oil directly into the manifold in intervals of 10% energy and injecting low-reactive ammonium hydroxide at 20%–50%. Utilizing the response surface methodology (RSM) approach, it was determined that for optimal operation in RCCI mode, an ideal ammonium hydroxide energy sharing (AHES) of 43% would account for the varying parameters and their effects on emissions and performance. The results of the experiments predicted a brake thermal efficiency (BTHE) of 34.85% and a brake specific energy consumption (BSEC) of 10.69 MJ/kWh. Meanwhile, a notable decrease in exhaust emissions was observed for HC, CO, CO2, NOxand smoke by 41.54%, 38.89%, 48.89%, 51.27% and 65.80% respectively when compared to conventional biodiesel combustion (CBC). The experimental result at maximum load operation with an AHES of 50% indicates that RCCI combustion led to an increase in thermal efficiency from 30.36% to 35.42%, and the in-cylinder pressure and heat release rate dropped from 83.42 bar to 59.64 bar and 78.68 kJ to 60.92 kJ, respectively. There was a significant reduction in HC, CO, CO2, NOxand smoke emissions recorded as 58.76 ppm, 0.11%v, 1.61%v, 442 ppm and 6.64 N, respectively, compared to CBC.

Superior wear resistance and a high level of tensile strength in piston ring materials are achieved using AA7075 surface composites (SCs) that are fabricated by reinforcing the steel slag (SS) particulates through proper selection of friction stir process (FSP) parameters using the multipass technique. The optical structure elucidates that fine and equi-axed grains are ascertained in the stir zone of the processed region, and by increasing the number of passes from one to three, a homogenous dispersion of particulates and a reduced grain size (9 µm) is obtained. In particular, a clear and defect-free interface is prominent on the resulting composite surface. Field emission – scanning electron microscopy (FESEM) identifies the dispersion of reinforcements, while X-ray diffraction (XRD) technique and energy dispersive spectroscopy (EDS) mapping confirm the existence of reinforcing elements. The Orowan strengthening effect and reduced oxygen content around the SiO2and CaO elements in the three-pass FSP SC specimen tend to increase its load-bearing capacity and result in superior hardness (353.3 VHN) and tensile strength (792.6 MPa). However, the same specimen exhibits a reduced percentage (%) elongation due to multiplied fragmentation of reinforcements, which eventually restricts the plastic movement of the AA7075 matrix. The SEM fracture morphology indicates that failure occurred through a combination of ductile and brittle modes. Furthermore, the SC specimen with two passes prominently decreases the wear rate (333 × 104mm3/m), which can be attributed to the commendable trilayer formation, and the worn morphology indicates the abrasive wear was the dominant wear mechanism. This fabricated specimen with high-strength characteristics can be beneficial for design engineers. During piston ring design, an increased level of the factor of safety can be achieved.

Selective Laser Melting (SLM) as an additive manufacturing process can fabricate near to net shape metallic components directly from Computer aided design models, which may be difficult to fabricate using conventional manufacturing methods. In this work, the powdered metals used as the raw material feedstock in the Selective Laser Melting (SLM) process were studied. SLM manufacturing processibility of nickel based super alloy, powders related to the particle Size Distribution (PSD), flow ability, mechanical properties and microstructures was investigated. Different powder characterisation methods were also investigated to establish which might be most useful for SLM application. Three different Inconel 625 (IN625) powder feedstock materials have been accounted for this study. Firstly, three different IN625 powders were fully characterised for chemical composition, particle size distribution and flow ability using different types of characterisation techniques. It has been found that the presence of any significant proportion of powder particles smaller than 10-μm diameter, leads to severe agglomeration and make SLM processing difficult. Secondly, coupons were manufactured using SLM from each powder with different process parameter, which were analysed for porosity and mechanical behaviour. Next, the scanning electron microscopy (SEM), electron back scattering diffraction (EBSD) are employed to investigate the microstructures. Finally, data analysis was employed on the data collected by metal powders characterization, SLM manufacturing, SEM/EBSD study and mechanical properties of the IN625. It has been observed that the powder characteristics, as well as SLM process parameters influences on the quality of the IN625 fabricated.

Electrodeposition of tin-bismuth alloys on polycrystalline copper electrodes has been studied from an acidic bath comprising SnCl4, Bi(NO3)3, citric acid, poly(vinyl alcohol) and betaine. Using linear sweep voltammetry (LSV) and chronoamperometry (CA), co-deposition of tin and bismuth from the above bath has been examined. Bismuth (III) ions get reduced in a single-step, three-electron-transfer reaction while tin (IV) ions undergo a two-step reduction through the formation of tin (II) ions. Nitric acid in the bath not only enhances solubility of the precursors but also decreases the peak potential separation between bismuth (III) and tin (II) ions. Through the introduction of various additives and variation in bath pH, co-deposition is preserved while the composition of tin in the obtained alloy is modified. The morphologies, composition and crystallinity of the deposits have been determined using scanning electron microscopy, inductively coupled plasma atomic emission spectroscopy and X-ray diffraction, respectively. A wide range of alloy compositions (from 14% to 75% tin), including the eutectic Sn-Bi alloy have been deposited. Novel morphologies such as yarns-of-spool have been obtained.

This study presents a systematic examination of the effects of bath additives and deposition conditions on the rates of electrodeposition of bismuth, obtained morphologies, and the ability of the bismuth films to detect trace concentrations of lead. Novel morphologies of bismuth are reported for the first time. The bath comprises bismuth nitrate, nitric acid, and a set of additives, viz., citric acid (complexant), poly(vinyl alcohol) (surface inhibitor), and betaine (grain refiner). Rotating disk electrode voltammetry and cyclic voltammetry have been used to determine the mechanism and rates of bismuth electrodeposition. Scanning electron microscopy is used to study deposit morphologies, while X-ray diffraction and X-ray photoelectron spectroscopy have been used to examine crystallinity and composition of the deposited thin films. Even in the presence of additives, it is seen that bismuth deposition is diffusion-controlled process with progressive nucleation–growth of crystallites, and the reduction is a single-step, three-electron-transfer, quasi-reversible reaction. The films deposited from the bath without additives comprise micrometer-sized, hexagonal rods with controlled aspect ratios (1.83–2.05). Baths containing citric acid produce films with flower-like structures and cracked grains, but with poor adhesion to copper substrate. Introducing poly(vinyl alcohol) significantly slows down bismuth deposition, increases the number of nuclei, produces cauliflower-like crystallites, and promotes adhesion to copper. Betaine smoothens these crystallites while retaining good adhesion. Pulsing the deposition current promotes growth of existing nuclei. In the absence of additives, fused flat disk-type spindles are seen. In the presence of additives, pulsed deposition results in sea-urchin-like morphologies. Adhesion of bismuth onto copper impacts the ability of the film to detect trace concentration of Pb2+ions in aqueous solutions using anodic stripping voltammetry. The films obtained from baths with additives through direct current plating show the best sensor response for 50 ppb Pb2+.