Abstract: Considering the issues involved in industrial cutting and machining systems, and, in particular, the problems arising from the use of cutting fluids in these systems, this study presents the results of an analysis that points to a safe and efficient way to reduce contaminated microbial cutting fluids using ultraviolet radiation. The study proposes a transmitter system of simple ultraviolet radiation, safe and easy to obtain. The results of this study showed that the action of ultraviolet radiation on microorganisms in metalworking fluids is very effective and leads to a significant reduction of the load of microorganisms. In addition, no changes were observed during the experimental period that would lead to impairments in the performance of the activities of the cutting fluid used. Given the results, we can conclude that the use of ultraviolet radiation in the prevention and control of contamination is an important contribution to the durability of cutting fluids in machining and grinding operations.
Abstract: Tribofilms are dynamic structures that form at the interface during frictional sliding. These films play a significant role in friction control, particularly under heavy loaded/high temperature conditions, such as those found at the cutting tool/chip interface. The thermodynamic aspects of tribofilm formation are discussed here. Thermodynamic analysis of entropy production during friction shows that there are two types of tribofilms that affect the wear behavior of a cutting tool: (1) tribofilms forming as a result of the surface modification of the cutting tools with further tribo-oxidation; and (2) tribofilms that form as a result of material transfer from the contacting frictional body (the workpiece) during the tool/chip interaction. Experimental examples are presented, outlining the beneficial role of both types of tribofilms.
Abstract: The role of surface protective additives becomes vital when operating conditions become severe and moving components operate in a boundary lubrication regime. After protecting film is slowly removed by rubbing, it can regenerate through the tribochemical reaction of the additives at the contact. However, there are limitations about the regeneration of the protecting film when additives are totally consumed. On the other hand, there are a lot of hard coatings to protect the steel surface from wear. These can enable the functioning of tribological systems, even in adverse lubrication conditions. However, hard coatings usually make the friction coefficient higher, because of their high interfacial shear strength. Amongst hard coatings, diamond-like carbon (DLC) is widely used, because of its relatively low friction and superior wear resistance. In practice, conventional lubricants that are essentially formulated for a steel/steel surface are still used for lubricating machine component surfaces provided with protective coatings, such as DLCs, despite the fact that the surface properties of coatings are quite different from those of steel. It is therefore important that the design of additive molecules and their interaction with coatings should be re-considered. The main aim of this paper is to discuss the DLC and the additive combination that enable tribofilm formation and effective lubrication of tribological systems.
Abstract: Abrasive resistant coatings have been widely used to reduce or eliminate wear, extending the lifetime of products. Abrasive resistant coatings can also be used in certain environments unsuitable for lubrications. Moreover, abrasive resistant coatings have been employed to strengthen mechanical properties, such as hardness and toughness. Given recently rapid development in abrasive resistant coatings, this paper provides a review of major types of abrasive coatings, their wearing mechanisms, preparation methods, and properties.
Abstract: Lubricant additives, based on inorganic nanoparticles coated with organic outer layer, can reduce wear and increase load-carrying capacity of base oil remarkably, indicating the great potential of hybrid nanoparticles as anti-wear and extreme-pressure additives with excellent levels of performance. The organic part in the hybrid materials improves their flexibility and stability, while the inorganic part is responsible for hardness. The relationship between the design parameters of the organic coatings, such as molecular architecture and the lubrication performance, however, remains to be fully elucidated. A survey of current understanding of hybrid nanoparticles as lubricant additives is presented in this review.
Abstract: Lubrication plays a key role in successful manufacturing of pharmaceutical solid dosage forms; lubricants are essential ingredients in robust formulations to achieve this. Although many failures in pharmaceutical manufacturing operations are caused by issues related to lubrication, in general, lubricants do not gain adequate attention in the development of pharmaceutical formulations. In this paper, the fundamental background on lubrication is introduced, in which the relationships between lubrication and friction/adhesion forces are discussed. Then, the application of lubrication in the development of pharmaceutical products and manufacturing processes is discussed with an emphasis on magnesium stearate. In particular, the effect of its hydration state (anhydrate, monohydrate, dihydrate, and trihydrate) and its powder characteristics on lubrication efficiency, as well as product and process performance is summarized. In addition, the impact of lubrication on the dynamics of compaction/compression processes and on the mechanical properties of compacts/tablets is presented. Furthermore, the online monitoring of magnesium stearate in a blending process is briefly mentioned. Finally, the chemical compatibility of active pharmaceutical ingredient (API) with magnesium stearate and its reactive impurities is reviewed with examples from the literature illustrating the various reaction mechanisms involved.