The demand for Electric Vehicles (EVs) is currently increasing to reduce carbon emissions and mitigate the environmental impacts. However, this transition presents new lubrication challenges due to unique operational characteristics of EV transmission such as higher torque at low speeds and elevated operating temperature. Hence, this study investigates the influence of chemically modified palm oil ester and mineral oil blend ratios, with and without ATF additive package on the physicochemical, rheological and tribological performance of the resulting formulations. The blends also benchmarked against a commercial ATF. The physicochemical properties including viscosity, density, flash point and viscosity index were systematically evaluated. Tribological performance was assessed using four-ball wear test at 75 degrees C. The result reveals that palm oil ester blends exhibit varying responses in terms of coefficient of frictions and wear scar diameter. These findings were influenced by the relative proportions of palm oil ester, mineral oil and additive content in the formulation. The formulations also comparable with the benchmark commercial ATF.
M303 alloy steel is a martensitic chromium steel that has high corrosion and wear resistant in addition to high toughness. Hence, this material is widely used in plastic injection molds, hot runner systems, automotive and locomotive components. This study was conducted to investigate the effect of machining parameters when turning M303 alloy steel at high cutting speeds under cryogenic conditions, in response to the locomotive industry's demand for high-precision machining of this material. Experiments were designed using the Taguchi L9 method, varying feed rates (0.1, 0.15, and 0.2 mm/rev), depths of cut (0.2, 0.4, and 0.6 mm), and cutting speeds (260, 300, and 340 m/min), while employing Al2O3/TiCN-coated carbide tools. Tool wear progression and mechanisms were characterized using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX). Results revealed that the coated carbide tool effectively inhibited rapid wear progression at a low cutting speed (260 m/min), feed rate of 0.1 mm/rev, and depth of cut 0.4 mm, achieving a maximum tool life of 81.1 minutes. SEM-EDX analysis identified adhesion, oxidation, chipping, and abrasion as the dominant wear mechanisms, with cutting-edge chipping, built-up edge formation, and catastrophic tool flaking observed at higher depths of cut. Tool wear mechanisms were also studied, revealing that cutting-edge chipping, abrasion, adhesion, and the formation of build-up edges contributed to completing tool life criteria. Additionally, catastrophic failure was observed, which is attributed to the flaking of the cutting tool material, especially at higher depths of cut. This research provides valuable insights into optimizing the machining of M303 for enhanced efficiency and tool longevity.
Martensitic stainless steel AISI 420 is widely used in steam turbine components due to its high strength and corrosion resistance; however, it remains susceptible to solid particle erosion (SPE) under high-temperature, high-velocity conditions. This study examines the erosion behavior of AISI 420 using a Taguchi L9 orthogonal array with three control factors: impingement angle (30 degrees, 60 degrees, 90 degrees), temperature (400 degrees C, 500 degrees C, 600 degrees C), and particle velocity (50 m/s, 75 m/s, 100 m/s). Erosion tests were conducted following ASTM G76 using angular alumina particles (50 +/- 5 & micro;m) at a constant feed rate of 5 g/min. Signal-to-noise (S/N) ratio analysis based on the "smaller-is-better" criterion identified 50 m/s, 90 degrees, and 500 degrees C as the optimum conditions. ANOVA indicated that particle velocity had the most significant effect, contributing 81.61% of the total variance (p = 0.028). Although temperature and impingement angle were statistically insignificant, trends showed lower erosion at normal impact and intermediate temperatures due to reduced shear stress and oxide film formation. FESEM and EDX analyses confirmed minimal damage and increased oxygen and aluminum content under optimal conditions, validating the protective role of thermally induced oxides. The findings provide insights for improving AISI 420 durability in erosive, high-temperature turbine environments.
White layer formation on machined surfaces, particularly during hard turning is often used as an indicator of thermal and mechanical damages. However, accurate interpretation of white layer presence remains a challenge, especially when imaging artifacts or preparation-induced changes are not accounted for. This study investigates the influence of sample preparation through wire cut electric discharge machining (WEDM) and SEM imaging on the appearance of white layers in hard-turned samples of AISI 4340 steel processed under cryogenic and dry environments using both fresh and worn carbide tools. SEM analysis of cross-sectioned samples revealed prominent white layers with no visible subsurface plastic deformation on the samples machined with fresh tools. In contrast, worn-tool samples showed clear signs of surface plastic deformation, but with less distinct white layers. Subsequent validation through optical microscopy of etched top machined surfaces prior to WEDM sectioning, revealed well-preserved feed marks and microstructure, contradicting the SEM-detected white layers. These findings suggest that wire-cut EDM white layers, as well as scanning electron microscopy (SEM) imaging secondary electron contrast and edge rounding can mimic white layer morphology. Thus, this study emphasizes the importance of critical analysis and cross-verification in microstructural evaluations to avoid false-positive identification of white layers.
Developing bio-based lubricants from banana peel oil is emerging as a promising alternative to conventional lubricants. Infusing this biolubricant with graphene nanoparticles has the potential to enhance its tribological performance significantly by creating a tribofilm at the contact surface. This study aims to investigate the effectiveness of graphene-infused banana peel oil, with a focus on its tribological behaviour. Oil was extracted using Soxhlet extraction, and nanoparticle infusion was accomplished using ultrasonic homogenization. Tribological tests were conducted using the 4-ball tribometer to record the coefficient of friction (CoF) and wear scar diameter (WSD). The results showed that Sample 8 (0.5 vol%, 20 minutes, industrial graphene) obtained the best tribological performance, with the lowest CoF (0.0825) and WSD (137 & micro;m), while Sample 13 (0.3 vol%, 20 minutes, technical graphene) presented the highest COF (0.0939). Sample 14 (0.3 vol%, 20 minutes, technical graphene) exhibited the most severe wear in WSD value (170 & micro;m). In addition, Sample 8 demonstrated Graphene's crystal structure and its types having optimised composition to help reduce friction and wear by forming a protective layer that minimised direct surface contact. Furthermore, the developed bio-lubricants also demonstrated similar lubricant performance when compared to conventional engine oil.
This study investigates the wear behavior of a new nozzle made of Stainless Steel (SS) 316L using an accelerated wear test under machining condition employing different abrasives namely Garnet and Silicon Carbide (SiC). The research focuses on the newly designed nozzle consisting of two detachable parts; an inlet and an outlet with a special feature for easy replacement. Preliminary experiments were carried out to evaluate the wear rate, wear patterns, and surface degradation using SEM analysis. Results showed that the nozzle tested with SiC experienced more severe erosion, indicated by a greater expansion in bore size, compared to the one tested with Garnet. SEM, mass loss, elemental analysis, and surface roughness results reveal that SiC abrasives cause significant nozzle wear through combined material removal and particle embedding. The surface roughness varies along the nozzle, with the inlet showing the highest erosion. These findings highlight the need for appropriate abrasive selection and nozzle design to reduce wear and extend service life.
Mineral oil lubricants pose environmental and health risks due to their non-biodegradability. Consequently, biodegradable lubricants from vegetable oils have gained attention as alternatives. However, their poor thermooxidative stability limits industrial use. Additives and nanoparticles have been used to improve performance but often compromise biodegradability. To address this, palm oil-based trimethylolpropane ester (PO-TMP) and coconut oil (CO) were selected for their complementary lubrication properties. This study evaluates blends in three ratios (25, 50, and 75 vol% CO, designated as C25, C50, and C75) without chemical additives, using SAE 40 mineral oil as a benchmark. Physical properties (density, viscosity, and viscosity index) were measured according to ASTM standards, and tribological tests were conducted at varying temperatures and frequencies using a Linear Reciprocating Tribometer. The inclusion of 25 vol% PO-TMP in C75 enhanced the viscosity index by 20%, lowered the COF by 12%, and reduced the wear scar diameter by 17% relative to coconut oil, with the COF (0.117) also 7% lower than that of mineral oil (0.126). These results show that incorporating 25 vol% PO-TMP improves coconut oil's tribological performance without chemical additives, producing a fully biodegradable blend with performance comparable to mineral oil and strong potential as a sustainable lubricant alternative.
Preparation of hydrophobic coatings on metal materials is a promising development for reducing friction and wear under tribology conditions. This work investigates the behaviour of hydrophobic stainless steel surfaces, laser-textured with Cu layer addition for modified surface energy and its effects on tribology performance. Disc samples were prepared by electroplating a thin Cu layer directly onto the stainless steel surface before laser-texturing. The laser parameters are varied at different scanning speeds, power and hatch distances. The micro and nano structures were analysed by a laser confocal microscope and a scanning electron microscope. The surface wettability was assessed through static water contact angle, while the Owens-Wendt method is used to measure the surface energy. Energy dispersive x-ray spectroscopy analysis confirmed the presence of Cu, and a direct correlation between Cu content and surface energy was observed. The hydrophobic laser-textured samples were found to possibly reduce friction compared to the untextured and uncoated samples. An improvement in performance is attributed to the decrease in contact area and the existence of voids as a "cushion" against adhesion and damage. The findings are significant for designing low surface energy adhesion for bio-tribology applications, where controlled friction and reduced biofouling are critical.
Lubrication in automatic transmissions is essential for reducing friction and wear, ensuring efficiency, durability, and smooth gear shifting. Although ATF provides these functions, variations in elemental additives can influence its performance, making it important to examine how additive composition affects wear behaviour. This study aims to identify the relationship between elemental additive composition and wear-preventive properties in five ATFs. Viscosity was measured according to ASTM D445, elemental composition following ASTM D6595, chemical properties following ASTM E1252-98, and tribological performance follows ASTM D4172. The results indicate that ATFs containing higher concentrations of phosphorus (up to 520.58 ppm), zinc (up to 343.52 ppm), calcium (up to 287.52 ppm), and boron (up to 371.48 ppm), particularly ATF C and ATF E, exhibited lower and more stable friction coefficients ranging from 0.079 to 0.087 compared to ATF A and ATF D. FTIR spectra confirmed phosphate, ester, and antioxidant groups, which enhance thermal and oxidation stability. These findings show that ATF C and ATF E provide the best balance of chemical composition, viscosity stability, and tribological performance. The results highlight the strong link between additive composition and wear-preventive effectiveness, underscoring the role of additives in ensuring smooth operation, durability and reliable protection of automatic transmissions.
Moisturisers function as topical lubricants that help optimise skin hydration and maintain the balance of sebum production. This study aims to characterise moisturisers based on their diverse textures and formulations. Six commercially available moisturisers were selected for both chemical and mechanical analysis. To evaluate their performance as skin lubricants, three key physicochemical properties were investigated: pH level, moisture content and viscosity. The pH was measured using a pH meter, moisture content was assessed using a Thermogravimetric analyser and viscosity was determined with a Vibro viscometer at room temperature. The pH values of moisturisers were plotted against the pH range of healthy skin for comparison. Additionally, the relationship between moisture content and viscosity was illustrated using a line graph. In conclusion, chemical and mechanical testing effectively characterises moisturisers in terms of pH, moisture content and viscosity. These parameters offer valuable insights into the potential safety and efficacy of skin lubricants, as well as opportunities for formulation enhancement.
This study presents a comparative evaluation of the erosion performance of stainless steel 304 (SS304) and carbon steel 1045 (CS1045) under waterjet peening process. The investigation focused on surface roughness and erosion characteristics under varying waterjet impingement parameters, including the number of jet passes, pressure, feedrate and stand-off distance. ANOVA results showed that the number of jet passes was the most influential parameter affecting surface roughness followed by pressure, feedrate and standoff-distance for both materials. In terms of surface roughness, CS1045 consistently exhibited greater value than SS304, primarily because of its lower hardness and reduced resistance to plastic deformation. Although CS1045 showed only slightly more severe material erosion overall, continuous surface degradation was particularly evident at higher pressures and increased jet passes. Hardness measurements further revealed that CS1045 exhibited a substantially greater increase in hardness compared to SS304 under identical waterjet conditions. Fractographic analysis revealed a predominantly ductile erosion mechanism in SS304, characterized by fibrous and dimpled fracture surfaces. Conversely, CS1045 displayed a mixed brittle-ductile erosion mode, with cleavage features and river patterns indicative of brittle fracture. These observations highlight the complex nature of material response to waterjet impact, where factors such as microstructure, hardness, and energy absorption mechanisms significantly influence erosion behaviour. The findings offer valuable insights for selecting suitable materials in applications involving high-pressure fluid impact and surface treatment processes.
The development of biodegradable greases has garnered significant interest due to the environmental concerns associated with conventional mineral-based lubricants. In this study, the characteristics of palm olein-based grease formulated with microcrystalline cellulose (MCC) thickener were investigated and compared with a conventional mineral-based grease to evaluate its potential as a biodegradable alternative in terms of wear and friction performance. Thermogravimetric Analysis (TGA) was performed to access the thermal stability and decomposition behavior of the greases, while Fourier Transform Infrared Spectroscopy (FTIR) was conducted to identify the functional groups present in the palm olein-cellulose formulation. Tribological testing was conducted using a pin-on-plate tribometer, and the worn surface morphology was examined using Scanning Electron Microscopy (SEM). The penetration test indicated that the formulated palm olein grease corresponds to NLGI 1 grade. TGA analysis demonstrated good thermal stability and FTIR confirmed the presence of hydroxyl groups from cellulose and fatty acids. Tribological results revealed that the formulated greases exhibited lower wear and friction compared to the conventional mineral grease, indicating the potential of palm olein-based grease as a sustainable and biodegradable lubricant.
AISI 316L stainless steel (SS316L) is widely used in biomedical implants due to its corrosion resistance and biocompatibility. However, long-term use may lead to metallic ion leaching and bacterial colonization. Tantalum (Ta) coatings deposited via physical vapor deposition (PVD), particularly magnetron sputtering, offer a promising surface modification approach due to their chemical inertness and stable oxide formation. In this study, SS316L substrates were first prepared through dry turning to obtain clean, oxide-free surfaces, followed by magnetron sputtering of Ta films under controlled argon atmosphere. Yet, the thermal stability of such coatings, particularly after post-deposition heat treatment, remains insufficiently understood. This work investigates the morphological evolution and surface quality of Tacoated SS316L annealed at 250 degrees C, 450 degrees C and 650 degrees C using FESEM, EDX and AFM. Results revealed that coatings remained structurally and compositionally intact up to 450 degrees C, showing fine-grain morphology, limited elemental diffusion, and nanoscale roughness (Ra approximate to 2-3 nm). At 650 degrees C, grain coarsening and Ta depletion led to coating failure (Ra > 22 nm). These findings demonstrate that Ta coatings exhibit thermal stability up to 450 degrees C, beyond which degradation occurs, compromising biomedical applicability. The study provides new insight into optimizing post-annealing parameters for achieving thermally stable, smooth Ta coatings on SS316L implants.
Fused Deposition Modelling (FDM) is the most common 3D printing method, which the mechanical properties and wear performance can be affected by various printing parameters and the addition of recycled materials. Therefore, this study aims to support sustainable use of recycled materials by investigating the effect of wall line count of blended recycled polyethylene terephthalate /high density polyethylene (rPET/HDPE) on mechanical and tribological properties using FDM process. The ratios of rPET:HDPE used in this work was 5:95 and blended using extrusion process to fabricate the 3D filament. Then, thermal analysis and surface morphology were examined to observe the compatibility of these blended materials. Moreover, the mechanical and wear performance of 3D-printed samples with 5, 10, and 15 wall line counts were evaluated using tensile and reciprocating wear test, respectively. It shows that the addition of 5% rPET into HDPE produced a higher melting temperature compared to pure HDPE. In terms of mechanical properties, the 10 wall line counts exhibit the best mechanical and tribological properties. The 10 wall line counts produced two times higher tensile strength and better wear resistance compared to the 5 and 15 wall line counts. Overall, the results show that varying wall line counts can affect the mechanical and tribological properties.
Dry machining of hardened steel generates heat, wears tools quickly, and reduces surface quality, with few studies comparing up/down milling under dry, highspeed conditions. This study examines effects of up/down milling on surface roughness and tool life during dry milling of hardened AISI 4340 steels. Tests followed Taguchi L9 array, using cutting speed (V = 300-400 m/min), feed rate (F = 0.15-0.3 mm/tooth), depth of cut (DOC = 0.3-0.5 mm) and width of cut (WOC = 0.2-0.5mm). For up milling, F impacted surface roughness most (58.07%), followed by V (34.95%). In down milling, F dominated (77.69%), with DOC at 10.34%. Minimum surface roughness for up milling (0.198 mu m) occurred at V = 400 m/min, F = 0.15 mm/tooth, DOC = 0.4 mm. For down milling, best surface (0.165 mu m) was achieved at identical parameters. V primarily affected up milling tool life (72.16%) with longest life (4.11 minutes) at V = 300 m/min, F = 0.15 mm/tooth, WOC = 0.2 mm and DOC = 0.3 mm. In down milling, F was the main factor (99.85%), producing longest tool life (25.33 minutes) under same parameters. These results provide insights for machining hardened AISI 4340 steel and developing efficient practices.
The lubricating oil industry plays a key role in improving the efficiency and durability of mechanical and automotive systems. This study uses a multi-objective optimization method to find the best bio-nanolubricant made from Botryococcus braunii algae oil, Oleic acid as surfactant, and hybrid nano-additives. Several samples were tested for important properties like viscosity, flash point, acid value, friction coefficient, and wear rate. The objective of this study is to find a formulation that balances performance and reliability. The MULTIMOORA method is deployed due to its robustness in handling conflicting criteria well without bias and its independence from normalization and weighting biases by comprising the ratio analysis, reference point analysis and the full multiplicative form. Attributes of each sample are ranked and normalized through this framework to ascertain an objective selection. This analytical methodology offers a reliable decision-making strategy for the lubricant formulation and selection in multi-criteria environments. This method ranked each sample using nine key attributes density, kinematic viscosity, flash point, pour point, cloud point, acid value, friction coefficient, wear and specific wear rate. Our results show that adding graphene oxide and MWCNTs improves wear and friction resistance. The MULTIMOORA optimized formulation, B99O1G0.5C0.5, demonstrated stronger stability, lower friction, and less wear. It outperformed commercial 20W-40 oil, offering better wear resistance and thermal stability, making it suitable for demanding mechanical uses. This is the first study to apply MULTIMOORA for optimizing bio-nanolubricants and provides a reliable approach for multi-criteria lubricant selection.
This study investigates the machining challenges of AISI 4340 steel, a material highly utilized in heavy industries for its strength and wear resistance but difficult to machine due to hardness, high tensile strength, and poor thermal conductivity. While High-Speed Machining (HSM) offers potential productivity benefits, heat generation at speeds above 300 m/min remains a key issue that shortens tool life. Existing research has also not sufficiently explored machinability at cutting speeds up to 400 m/min combined with very low feed rates. To address this, Finite Element Analysis (FEA) was performed using ANSYS Explicit Dynamic to simulate turning operations on AISI 4340 steel at speeds from 300 to 400 m/min. Key factors such as cutting force and temperature at the tool-chip interface were analyzed relative to machining parameters. The findings reveal cutting speed mainly affects cutting temperature, while feed rate and depth of cut mainly influences cutting force. Cutting force results qualitatively matched prior experimental data trends, while the highest cutting temperature under highest speed also correlates with the shortest tool life. This work offers critical insights into machining behavior for understudied high-speed conditions, supporting efforts to optimize tool life and develop effective strategies for sustainable machining of AISI 4340 steel.
This study evaluates wear rate predictions by comparing experimental results with Finite Element Analysis (FEA) simulations, focusing on the influence of track radius. Regression models were developed to analyze the trends, while residual analysis identified deviations between the two approaches. A correlation matrix highlighted significant relationships between wear rate, pressure, and sliding distance. Confidence interval analysis confirmed the reliability of both models, though polynomial regression provided a more accurate representation of wear rate trends than linear models. While FEA predictions are closely aligned with experimental data, some discrepancies suggest the need for further refinement in computational modeling to improve accuracy. Future work will focus on enhancing FEA simulations and expanding experimental validation for better predictive reliability.
Hydrogen-fuelled internal combustion engines (H2ICEs) emit significant quantities of water vapour, which can condense and accumulate in the crankcase. Under mechanical agitation, this moisture may form water-in-oil emulsions, potentially impairing lubricant performance. This study simulates such conditions by emulsifying synthetic SAE 5W-40 engine oil with up to 40 wt% deionised water, to mimic shear-induced water contamination in H2ICEs. For the emulsified lubricants, viscosity increased with water content, and the Vogel-Fulcher-Tammann (VFT) equation effectively described their temperature dependence. Reduced viscosity-temperature sensitivity observed at higher water levels resembled high-viscosity-index behaviour, indicating enhanced thermal stability. Tribological tests revealed that moderate water content (less than 20 wt%) decreased friction and wear due to increased film thickness, attributing to higher viscosity. However, corrosion escalated sharply beyond 20 wt% water contamination, posing long-term durability risks. These findings establish critical thresholds, where water contamination shifts from beneficial to detrimental. The results emphasised the necessity to optimise lubricant formulations for H2ICEs by balancing viscosity, wear protection, and corrosion resistance in moisture-rich environments.
In sectors such as maritime, mining, and power generation, components frequently encounter severe tribological and corrosive environments that accelerate surface degradation. Titanium dioxide (TiO2) coatings, particularly when applied via thermal spray techniques such as Atmospheric Plasma Spray (APS), Suspension Plasma Spray (SPS), and High-Velocity Oxy-Fuel (HVOF), demonstrate significant potential for wear and corrosion protection. This review focusses on the influence of TiO2 crystalline phases, particularly rutile, on hardness, wear resistance, and chemical stability. The emphasis is on TiO2-based composites reinforced with oxides (such as Al2O3, Cr2O3, and ZnO) or carbides (such as WC). These compounds enhance the durability of the composites by synergistically increasing their strength. The processing parameters, including temperature, voltage, and cooling rate, are highlighted as critical factors influencing phase stability and tribological outcomes. Furthermore, innovative methods like hybrid MAO-laser surface texturing and nanostructured sol-gel deposition are acknowledged as promising but inadequately explored strategies for tailoring microstructure and improving service longevity. The findings indicate that rutile-rich TiO2 composites, when employed with contemporary deposition techniques, represent the optimal choice for fabricating next-generation wear-resistant coatings suitable for high-stress, high-temperature environments.
