Mubashir Gulzar

Tribological performance of nanoparticles as lubricating oil additives

The prospect of modern tribology has been expanded with the advent of nanomaterial-based lubrication systems, whose development was facilitated by the nanotechnology in recent years. In literature, a variety of nanoparticles have been used as lubricant additives with potentially interesting friction and wear properties. To date, although there has been a great deal of experimental research on nanoparticles as lubricating oil additives, many aspects of their tribological behavior are yet to be fully understood. With growing number of possibilities, the key question is: what types of nanoparticles act as a better lubricating oil additive and why? To answer this question, this paper reviews main types of nanoparticles that have been used as lubricants additives and outlines the mechanisms by which they are currently believed to function. Significant aspects of their tribological behavior such as dispersion stability and morphology are also highlighted.

Effect of Lubricant Formulations on the Tribological Performance of Self-Mated Doped DLC Contacts: a review

Abstract Diamond-like carbon (DLC) coatings have emerged as one of the most promising surface coatings for applications involving boundary lubrication regime. Some of the characteristics that distinguish DLC coatings from other hard coatings include high hardness, low friction coefficient, wear resistance, and chemical inertness. Because of their low surface energies, these coatings cannot react effectively with different lubricant constituents. Doping of DLC coatings with metals and nonmetals, such as titanium, tungsten, silicon, chromium, fluorine, and nitrogen, can improve their interaction with lubricants to form tribologically beneficial films. Many experimental studies have been conducted on different types of DLC coatings using various lubricant formulations in the last few decades. The results obtained from these experimental studies are very scattered and contradictory, so the data should be consolidated in a more organized and apprehensible manner. By doing so, tribological behavior of various DLC–lubricant combinations can be understood in a better way, and a more logical continuation of research on DLC coatings can be carried out. In this review paper, most widely investigated metal- and nonmetal-doped DLC coatings, such as Ti-DLC, W-DLC, Si-DLC, Cr-DLC, WC-DLC, and multilayered a-C:H/W-DLC coatings, are considered for evaluation. Tribological performance of the aforementioned DLC coatings, in combination with various base oils and lubricant additives, is analyzed by comparing their average friction and wear coefficient values, which have been calculated from published experimental data. Only self-mated doped DLC contacts are considered in this study to eradicate the interference of ferrous and nonferrous counterbodies.

Dispersion Stability and Tribological Characteristics of TiO2/SiO2 Nanocomposite-Enriched Biobased Lubricant

ABSTRACT The stable dispersion of nano-additives is highly desirable for the effective lubrication performance of nanolubricants. The compatibility of base oil with selected nano-additives is required for uniform and stable dispersion. This research evaluated the dispersion stability and tribological characteristics of nano-TiO2/SiO2 (average particle size 50 nm) as an additive in a biobased lubricant. The wear protection and friction reducing characteristics of the formulations were evaluated by four-ball extreme pressure tests and piston ring–cylinder liner sliding tests. Surface analysis tools, including scanning electron microscopy, energy-dispersive X-ray spectroscopy, and atomic force microscopy, were used to characterize the worn surfaces. Results showed that the nanolubricants demonstrated appreciable dispersion capability in the absence of a surfactant and an improvement in load-carrying capacity, antiwear behavior, and friction reduction capability.

A Review on Effects of Lubricant Formulations on Tribological Performance and Boundary Lubrication Mechanisms of Non-Doped DLC/DLC Contacts

ABSTRACT Tribological efficiency of industrial applications involving boundary lubrication regime can be improved to an appreciable extent by the deposition of hard coatings on interacting surfaces. Among such coatings, diamond-like carbon (DLC) coatings are considered to be one of the most suitable ones for the said role. DLC coatings possess a unique combination of physical, chemical, and material properties due to which they can help in minimizing friction-induced energy and material losses even under starved lubrication conditions. Since commercial lubricants are optimized for steel surfaces, therefore, a lot of experimental investigations were carried out to analyze the tribological compatibility of these lubricants with various DLC coatings. However, there is still a lack of understanding about how DLC coatings interact with conventional lubricant additives. Some researchers reported tribologically beneficial interactions between DLC coatings and formulated lubricants while others observed no such behavior. To address these inconsistencies, there is a need to rearrange the published data in a more apprehensible and organized manner with a special emphasis on the mechanisms responsible for a particular tribological behavior. In this way, it can be determined whether synergistic or antagonistic correlation exists between a particular DLC-lubricant combination and research on DLC coatings can be continued in a logical way. In this article, most widely investigated non-doped DLC coatings (ta-C, a-C:H, a-C, and ta-C:H) are tribologically analyzed. Average values of friction and wear coefficients are calculated for various DLC-lubricant combinations using already published data and compared to quantify the effectiveness of a particular lubricant additive in enhancing tribological characteristics of symmetrical non-doped DLC contacts. Moreover, tribological performance parameters of non-doped DLC coatings are compared with those of doped-DLC coatings to understand differences in their tribological behavior in combination with additives.

Investigation of the tribochemical interactions of a tungsten-doped diamond-like carbon coating (W-DLC) with formulated palm trimethylolpropane ester (TMP) and polyalphaolefin (PAO)

Modern day industrial applications involve rigorous operating conditions, which include high temperature, heavy applied loads, and starved lubrication conditions. In these scenarios, either the lubricant slips out of the contact or only a thin layer of lubricant resides between interacting surfaces. The deposition of diamond-like carbon (DLC) coatings possessing extreme wear resistance and ultra-low friction characteristics and using lubricants capable of physically adsorbing on the interacting surfaces can significantly improve the tribological performance. Due to their superior tribological characteristics, chemically modified vegetable oils, such as palm trimethylolpropane ester (TMP), are one of the potential candidates to be used as lubricant base-oils. To prove the suitability of TMP and DLC coatings for applications involving a boundary-lubrication regime, a logical step forward is to investigate their tribological characteristics in combination with conventional lubricant additives. In this study, the extreme pressure characteristics of TMP formulated with glycerol monooleate (GMO), molybdenum dithiocarbamate (MoDTC), and zinc dialkyldithiophosphate (ZDDP) in combination with steel/steel contact were investigated using a four-ball wear tester. In addition, the tribochemical compatibility of the abovementioned additives with TMP and a tungsten-doped diamond-like carbon coating (W-DLC) was also analyzed using a universal wear testing machine. For comparison, additive-free and formulated versions of polyalphaolefin (PAO) were used as a reference. Moreover, various surface characterization techniques were used to investigate the mechanisms responsible for a particular tribological behavior. TMP-based lubricants exhibited superior extreme pressure characteristics and friction performance as compared to those containing PAO. An improvement in the tribological performance was observed when W-DLC-coated surfaces were used instead of uncoated-surfaces irrespective of the lubricant formulation.

The effect of particle size on the dispersion and wear protection ability of MoS2 particles in polyalphaolefin and trimethylolpropane ester

The effect of particle size and surfactant on dispersion stability and wear protection ability was experimentally evaluated for polyalphaolefin (PAO 10) and bio-based base oil (palm trimethylolpropane ester) added with molybdenum disulfide (MoS2) particles. Nanolubricants were developed by adding 1 wt% of MoS2 particles that varied in size. In addition to the variation in particle size, an anionic surfactant was also used to analyze its interaction with both types of nanoparticles for stable suspensions and for the related effects on the antiwear characteristics. The wear protection characteristics of the formulations were evaluated by four-ball extreme pressure tests and piston ring on cylinder sliding wear tests. The wear surfaces were analyzed by scanning electron microscopy along with an energy-dispersive X-ray and an atomic force microscopy. The MoS2 nanoparticles with a nominal size of 20 nm exhibited a better load-carrying capacity, while better sliding wear protection was provided by nanoparticles with a nominal size of 50 nm.

Tribological compatibility analysis of conventional lubricant additives with palm trimethylolpropane ester (TMP) and tetrahedral amorphous diamond-like carbon coating (ta-C)

Modern industrial applications involve rigorous operating conditions due to which lubricant either slips out of the contact or its thin layer resides between the interacting surfaces. Deposition of diamond-like carbon coatings and using lubricants capable of physically adsorbing on the interacting surfaces can significantly improve tribological performance. In this study, tribological compatibility of glycerol mono-oleate, molybdenum dithiocarbamate and zinc dialkyldithiophosphate with palm trimethylolpropane ester and tetrahedral amorphous diamond-like carbon coating has been investigated using universal wear testing machine. For comparison, additive-free and formulated versions of polyalphaolefin were used. Moreover, spectroscopic techniques were used to investigate mechanisms responsible for a particular tribological behavior. Among base oils, trimethylolpropane ester proved to be more effective in enhancing friction performance and mitigating wear of contacts when one of the interacting surfaces was ferrous-based. Self-mated tetrahedral amorphous diamond-like carbon coating surfaces resulted in lowest values of friction and wear coefficient of balls.

Antiwear Behavior of CuO Nanoparticles as Additive in Bio-Based Lubricant

This work presents and discusses the anitwear characteristics of surface modified CuO nanoparticle suspensions in bio-based lubricant. 1.0 wt% unmodified as well as surface modified CuO nanoparticles (nominal size of 50 nm), were dispersed in base oil using an ultrasonic probe. Wear protection was evaluated by using Four-Ball Extreme Pressure (EP) testing and sliding wear tests. The scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) analysis of the worn surface shows that: surface modification helped to improve the dispersion stability of CuO nanoparticles and related suspension show high EP characteristics in terms of load wear index and low cylinder liner wear due to surface mending effect of nanoparticles.

Geometric Modeling of the Frequency of an Acoustic Detonation Pressure Wave in a Standard Spark Ignition Engine

In an archetypal engine the detonation frequency is usually analyzed using an overly simplistic model, incorporating only the rudimentary parameters (modeling the combustion chamber as a right circular cylinder). The research work is to develop a broader state space geometric model to discern the detonation frequency in a standard Otto engine based on engine conformation parameters. The intent of this project is to model the detonation event using a broader state-space i.e.to build on Draper’s Acoustic Wave Pressure formula and develop a sound underlying mathematical structure manifesting the models intricacies. The mathematical structure is predicated on standard wave equation, this mathematical generality makes it a potential candidate for future investigations into developing a superposition model using acoustic wave theory.

Anatomization of Stresses on a V-12 Engine Crankshaft Vulnerable to Varying Imposed Forces

Crankshaft is an important component of an engine with intricate geometry which converts the linear displacement of piston into rotary motion. Since the crankshaft is predisposed to massive loads during combustion cycles, so different factors like endurance has to be kept in mind while designing crankshaft. Keeping in view the above scenario, the main motive of this paper is to do the fatigue analysis so that we can analyze various factors that are affecting the service life of crankshaft.