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.
