Genesis and stability of tribolayers in solid lubrication: case of pair DLC-stainless steel

AbstractThe morphology, dimensions and chemical composition of tribolayers strongly depend on the pressures and temperatures acting on the contact. They are formed by reactions between surfaces in contact with each other as well as with the atmosphere, lubricants and possible contaminants. In this paper, the influence of test time (180, 500, 1000 and 2500h) on the formation and characteristics of tribolayers in pairs of DLC-stainless steel that were tested under an atmosphere of refrigerant gas R134a and without lubricating oil was analyzed. The characterization was performed using scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) (morphology and chemical composition) and white light interferometry (thickness). The tribolayer thicknesses ranged from 100 to 500nm, and they were composed of elements originating from mutual transfers between the tribological pairs, as well as oxides that were more pronounced on the stainless steel surface. The results show that the tribolayers are chemically stable, maintaining the same composition over time, and their thicknesses remained constant after 1000h of testing

Plasma debinding and sintering of metal injection moulded 17-4PH stainless steel

In this work, 17-4PH stainless steel parts processed in a Plasma Assisted Debinding and Sintering (PADS) furnace were characterised in terms of microstructure, final density, microhardness, carbon content and tensile behaviour. To determine whether these properties were satisfactory, the same characterisation procedure was conducted on the parts processed by conventional batch furnaces that are normally employed in Metal Injection Moulding industrial plants. The properties were in good agreement, and only slight differences like an extremely low carbon content (0.003% w/o) were observed. It has been seen that not only economical advances but also intricate materials with suitable responses may be obtained using PADS

Controlling the Solid-State Reaction in Fe-MoS₂ Self-Lubricating Composites for Optimized Tribological Properties

In this work, self-lubricating composites containing MoS2 and graphite dispersed in an iron matrix were produced by powder metallurgy and sintering. Previous studies demonstrate that MoS2 reacts with iron matrixes during sintering, making the production of Fe-MoS2 composites rather difficult. Therefore, this study focused on a potential solution to avoid or reduce this reaction, whilst still providing good tribological properties. Our results show that the addition of graphite retards the reaction of MoS2 with iron and that the combination of MoS2 + graphite results in composites with an optimized coefficient of friction associated with a low wear rate both in nitrogen and air atmospheres. Through adequate control of the lubricant’s particle size, composition, and processing parameters, self-lubricating iron-based composites with a low dry coefficient of friction (0.07) and low wear rate (5 × 10−6 mm3·N−1·m−1) were achieved