Tribological Evaluation of Lead-Free MoS2-Based Solid Film Lubricants as Environmentally Friendly Replacements for Aerospace Applications

Solid lubricants, such as MoS2 have been widely used in the aerospace industry with the primary purpose of reducing the friction and wear of tribological interfaces. MoS2 based solid film lubricants are generally doped with other compounds, which can help overcome some of their limitations related to environmental conditions. For instance, compounds like Sb2O3 and Pb have been traditionally used to improve the endurance life of these lubricants. However, with the recent zest in transferring to eco-friendly lubricants, there is a strong push to eliminate Pb based compounds. The main purpose of this work is to better understand the influence of Pb based compounds on the tribological behavior of MoS2 based solid film lubricants as well as to critically evaluate the performance of Pb free lubrication strategies. More specifically, the baseline ‘non-green’ lubricant was doped with Pb compound and Sb2O3 and the Pb compound in the ‘Green’ alternative lubricant was replaced by more Sb2O3. The wear test was done using a ball-on-disk tribometer for specific loads and for 5000 cycles. Ex-situ analysis was conducted using Scanning Electron Microscope (SEM), Atomic Force Microscopy (AFM), and micro-Raman to capture the interfacial processes of these lubricants at different loads. Overall, the non-green lubricant performed better in terms of the tribological behavior (i.e., lower friction and wear), which was attributed to the formation of a dense MoS2-based tribo-/transfer-film with the basal planes oriented in the parallel direction to the sliding. The finding on the interfacial phenomena provided critical insights into the development of novel green alternatives that may have the ability to replace Pb based compounds in the future for a sustainable environment.

Micro Textured Cutting Inserts with Solid Lubrication as Alternative Coolant to Mineral Oil-Based Cutting Fluid in Turning Operation

Turning process is a primary process in engineering industries and optimization of process parameters enhance the machining performance. Inconel 718 is a nickel-based superalloy, widely found applications in the manufacturing of blades, sheets and discs in aircraft engines and rocket engines. It provides toughness at low temperature, with stand high mechanical stresses at elevated temperature and creep resistance. In this work, turning process is carried out on Inconel 718 with micro whole textured cutting inserts filled with solid lubricants. Three different solid lubricants are used namely molybdenum-di-sulfide (MoS2), tungsten-di-sulfide (WS2) and calcium-di-fluoride (CaF2). Experiments are performed as per L9 orthogonal array. Statistical approaches such as orthogonal array, Signal-to-Noise (S/N) ratio and Analysis of Variance (ANOVA) are used to find the importance and effects of machining parameters. In this study, input parameters included are feed, cutting speed and depth of cut and output parameter includes surface roughness. Optimization of process parameters is carried out and the significance is estimated. The result suggested that WS2 followed by MoS2 and CaF2 given good surface finish value. Also, solid lubricant in machining enhances the sustainability in manufacturing.

Graham Wood. 6 February 1934—4 November 2016

Graham Wood was a world-leading corrosion scientist who bridged both the aqueous (electrochemical) corrosion and high-temperature oxidation branches of the subject. His analytical predictions of depletion and enrichment profiles in substrate and scale during preferential oxidation have long been confirmed in practice. He also demonstrated that transient oxides can be vital solid lubricants in oxidative friction and wear processes. He elucidated ionic transport in amorphous anodic films, leading to precise models of pore initiation, development and closure, thus allowing the strict design of anodic films for practical application. He set up, and headed, the Corrosion and Protection Centre at the University of Manchester Institute of Science and Technology (UMIST) and was instrumental in initiating the Corrosion and Protection Centre Industrial Service, which, respectively, became the world's largest academic centre on the study of materials degradation and the world's largest corrosion consulting organization. While keeping active in research, he held increasingly senior administrative roles, where he established a specialist graduate school and helped prepare UMIST to full independence from the Victoria University of Manchester.

Innovative electrical engineering developed for the transport industry by the Emperor Alexander I Petersburg State Transport University

Objective: To familiarize the general scientific community with the latest electrotechnical innovative developments for the transport industry, carried out by the scientists of the Emperor Alexander I Petersburg State Transport University in the period from 2000 to 2021. Methods: We used the methods of calculation of electromagnetic fields and circuits, mathematical analysis, mathematical physics and numerical methods in the development of the described devices and systems. Results: 101 We developed a pipeline high-speed magnetolevitation transport system with vehicle movement in a rarefied atmosphere, a series of pantograph pantographs for heavy-loaded and high-speed trains using solid lubricants and a contactless method of transmitting electrical energy, a plasma device for fine cleaning of circuit boards for microcircuits, a device for creating a comfortable climate in office premises, electrohydroimpulse installations designed for loosening frozen coal in gondola cars in winter, shock tests of wagons, escalators and travalators using linear electric motors, high-speed electric switches-breakers, heat generators based on an electromechanical converter with the functions of a heater and pump, a wagon generator with a forced excitation system, a pulse voltage generator, allowing to measure the pulse resistance of the grounding conductors of the contact network supports, a complex of installations for various purposes using ozone technologies, a system for laser monitoring of the integrity of tanks, a device for diagnosing the degree of corrosion of the fittings of contact supports, an electrohydroimpulse installation for impact welding, treatment plants, technology for recycling car tires, security systems of the main trackbed. Practical importance: The use of the described developments will increase energy efficiency, energy saving and safety of production processes in transport

Formation of Solid Lubricants during High Temperature Tribology of Silver-Doped Molybdenum Nitride Coatings Deposited by dcMS and HIPIMS

The coating system MoN-Ag is an interesting candidate for industrial applications as a low friction coating at elevated temperatures, due to the formation of lubricous molybdenum oxides and silver molybdates. Film deposition was performed by high-power impulse magnetron sputtering and direct current magnetron sputtering. To facilitate a future transfer to industry Mo-Ag composite targets have been sputtered in Ar/N2 atmosphere. The chemical composition of the deposited MoN-Ag films has been investigated by wavelength dispersive X-ray spectroscopy. Morphology and crystallographic phases of the films were studied by scanning electron microscopy and X-ray diffraction. To obtain film hardness in relation to Ag content and bias voltage, the instrumented indentation test was applied. Pin-on-disc tribological tests have been performed at room temperature and at high temperature (HT, 450 °C). Samples from HT tests have been analyzed by Raman measurements to identify possible molybdenum oxide and/or silver molybdate phases. At low Ag contents (≤7 at.%), coatings with a hardness of 18–31 GPa could be deposited. Friction coefficients at HT decreased with increasing Ag content. After these tests, Raman measurements revealed the MoO3 phase on all samples and the Ag2Mo4O13 phase for the highest Ag contents (~23–26 at.%).