Electric motors play a decisive role in electric vehicles by converting electrical energy into mechanical motion across various drivetrain components. However, failures in these motors can interrupt the motor function, with approximately 40% of these failures stemming from bearing issues. Key contributors to bearing degradation include shaft voltage, bearing current, and electric discharge material spalling current, especially in motors powered by inverters or variable frequency drives. This review explores the tribological and vibrational aspects of bearing currents, analyzing their mechanisms and influence on electric motor performance. It addresses the challenges faced by electric vehicles, such as high-speed operation, elevated temperatures, electrical conductivity, and energy efficiency. This study investigates the origins of bearing currents, damage linked to shaft voltage and electric discharge material spalling current, and the effects of lubricant properties on bearing functionality. Moreover, it covers various methods for measuring shaft voltage and bearing current, as well as strategies to alleviate the adverse impacts of bearing currents. This comprehensive analysis aims to shed light on the detrimental effects of bearing currents on the performance and lifespan of electric motors in electric vehicles, emphasizing the importance of tribological considerations for reliable operation and durability. The aim of this study is to address the engineering problem of bearing failure in inverter-fed EV motors by integrating electrical, tribological, and lubrication perspectives. The novelty lies in proposing a conceptual link between lubricant breakdown and damage morphology to guide mitigation strategies. The study tasks include literature review, analysis of bearing current mechanisms and diagnostics, and identification of technological trends. The findings provide insights into lubricant properties and diagnostic approaches that can support industrial solutions.

Surface topography is a critical parameter that can influence friction and wear in engineering applications. In this study, the influence of surface topography directionality on seizure and scuffing initiation during tribological interactions is explored. Hence, unidirectional sliding wear experiments were carried out in immersed lubrication conditions for various normal loads. The tribological interactions were studied using EN31-60 HRC flats and SAE52100-60 HRC pins in a sphere on flat configuration. The results show that, in some cases, the sliding interactions in the initial cycles lead to a high friction coefficient of up to ∼0.68 in lubricated conditions, which was termed as “peak friction”, and this was accompanied by scuffing. The existence of peak friction was found to be dependent on surface topography directionality, especially when the directionality in topography was parallel to the sliding direction. Continuous ratchetting was found to be the cause of peak friction, which was accompanied by seizure and scuffing. When the topography directionality was perpendicular or independent of the sliding direction, elastic shakedown occurred at earlier cycles and prevented peak friction initiation and scuffing and also facilitated for higher steady-state friction values.

The profound usage of Inconel X-750 in structural and high-pressure conditions mandates improved tribological properties. One of the methods to achieve this is through surface topography modifications. In this work, the viability of the shot blasting technique is explored to enhance the wear resistance of Inconel X-750. For this purpose, aluminum oxide particles with 80 mesh size were shot blasted on the superalloy surface at a constant pressure of 0.6 MPa. The 3D surface topography of Inconel X-750 alloy confirms substantial surface deformation and increased surface roughness after shot blasting. Furthermore, the surface characteristics of shot-blasted superalloy were meticulously examined using a string of techniques: optical profilometer, scanning electron microscope, and electron probe microanalysis. The tribological properties of Inconel X-750 before and after shot blasting were examined using a reciprocating tribometer with a ball-on-flat configuration. Results showed that shot blasting the superalloy has tremendously enhanced the wear resistance by ∼78%, which could be attributed to the reduced sliding contact area, enhanced surface hardness, and the hindrance in the transition of wear mechanism from abrasion tribo-oxidation to adhesion.

Cutting fluids are crucial to machining, providing essential lubrication and thermal management during the process. Commercial Cutting Fluids (CCF) are generally based on mineral oils, with emulsifiers and additives that are produced chemically. Green Cutting Fluid (GCF), which is generally based on biodegradable plant-based oils, is an emerging alternative to CCF and is eco-friendly, non-toxic, and sustainable. In the present work, the viability of a coconut oil-based GCF has been evaluated to determine its suitability and effectiveness across a wide range of machining operations, by mimicking the surface roughness of various machining operations. For this, Ti–6Al–4V samples were prepared with unidirectional surface roughness in the 111- to 1350-nm range; the roughness range of various machining operations. The behavior of the GCF and CCF, including their Wettability, Interfacial Tension, Surface Energy, and tribological lubrication effectiveness, were studied and compared over these surfaces. The results show that the concentration of cutting fluid and surface roughness greatly influence the wettability and surface energy, respectively. GCF has shown competitive performance in comparison with CCF, showing its potential as a viable alternative to CCF . The article also includes a discussion on the sustainability and Strengths, Weaknesses, Opportunities and Threats (SWOT) analysis of the GCF, and the work is in line with the United Nations Sustainable Development Goals (UN SDGs) 3, 11, 12, 13, and 15.

The benefits of surface textures on rolling and sliding tribological contacts have been an exciting field of study over the last three decades. Laser surface texturing (LST) is a comparatively newer texturing methodology that yields repeatable precise microtextures. A detailed overview of the available literature on the various works in this field is consolidated in this review. The main focus is on the effect of surface textures (with focus on laser ablation) for nonconformal contacts with elastohydrodynamic lubrication (EHL), as in rolling element bearings. A review of literature on textured contacts for the EHL regime, emphasizing its effect on friction, wear, rolling contact fatigue, vibration, texture geometry, and numerical simulation studies, is carried out with possibilities of future works. Basic details on LST processes and various parameters of the laser beam that determine the texture geometry are discussed. Being a field of continuing research, the review paper will aid in understanding the present developments and future directions in laser‐based surface texturing for nonconformal tribological contacts.