Effects of Using Alternative Extreme Pressure (EP) and Anti-Wear (AW) Additives with Oxy-Nitrided Samples

Abstract

Oxy-nitriding is a widely used industrial process aiming to improve the tribological properties and performance of components. Previous studies have shown the effectiveness of the treatment with friction and wear performance, but very few have focussed on optimising this behaviour. The lubrication properties of several EP and AW additives were examined to investigate their effectiveness in improving the tribological properties of the layers formed after treatment. Previous studies showed the presence of an oxide layer on the sample could improve the effectiveness of the sulphurised olefin (SO) and tricresyl phosphate (TCP) additives. The friction and wear behaviour of oxy-nitrided samples were analysed using a tribometer and surface profiler. Scanning electron microscope, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were employed to identify the morphologies and chemical compositions of the treated surface before and after testing. No real effect on friction was observed when using the SO or TCP additives, mostly due to lack of interaction with the less reactive iron nitride layer and their roles as anti-wear additives. However, when the zinc dialkyldithiophosphatecontaining lubricant was used, a higher friction coefficient was observed. Greater improvements in anti-wear properties with the presence of additives in comparison with only using base oil were reported, with the TCP additive producing the lowest wear rates. The study effectively demonstrated that the additive package type used could impact the tribological and tribochemical properties of oxy-nitrided surfaces.

Superlubricity achieved with two-dimensional nano-additives to liquid lubricants

“…Notably, a tribochemical reaction occurs during the sliding process in which the anions in ionic liquids such as PF  6 , BF  4 , and NTf  2 react with water to produce phosphates [85], borides [86], and sulfides [87] on the worn surface, respectively [36,88]. Owing to the excellent extreme pressure and anti-wear properties of phosphates, the tribochemical layer formed by PF  6 exhibits the best lubricating performance [89]. On the other hand, the cations in ionic liquids such as Li + , Na + , and K + possess quite different hydrated radii and hydration energies.…”

Biolubricant production via esterification and transesterification processes: Current updates and perspectives

“…The adsorption of additives physically or chemically to the surfaces of metal results in tribofilm, which consequently averts abrasive wear of the surface and reduces friction 117 . Due to the eco‐toxicity effects of some additives currently used, such as molybdenum dithiocarbamate (MoDTC) and zinc dialkyldithiophosphate (ZDDP), there has been a great interest in the use of eco‐friendly additives that may be of the organic or inorganic source 118 …”

“…Experts in tribology employ the science and notion of tribology studies concerning the interacting surface in relative motion to investigate friction, wear, and lubricity of lubricants 163 . Generally, friction is the resistance when two bodies are in motion resulting in wear and tear 118,119 . The studies and impact of tribology have expanded across diverse disciplines, which cannot be covered in this review.…”

“…117 Due to the eco-toxicity effects of some additives currently used, such as molybdenum dithiocarbamate (MoDTC) and zinc dialkyldithiophosphate (ZDDP), there has been a great interest in the use of eco-friendly additives that may be of the organic or inorganic source. 118 Recently, ionic liquids (ILs), polymers, and plantsourced compounds made up of heteroatoms and longchain fatty acids have shown great potential as additives of lubricants as well as biolubricants, hence remedying this environmental menace. In a most recent study by Kontham et al, 114 some novel thioether Schiff base additives (ie, containing substituted phenyl rings, sulphur, and nitrogen), which were produced from 10-undecenoic acid and different aromatic aldehydes, enhanced the tribological performance and oxidative stability properties of the lubricant base oil even at low concentration of 0.8 wt%.…”

Experimental investigation of tribological effect on vegetable oil with CuO nanoparticles and ZDDP additives

“…Results found that anti-wear protection was reduced from the depleted ZDDP additives during the tribological contact with piston rings and piston skirt region. Khan et al (2018) investigated the tribological performance of oxy-nitrided samples with anti-wear and extreme pressure additive sulphurized olefin (SO), tricresyl phosphate (TCP) additives and ZDDP. SO or TCP additives have no effect on friction because of lack of interaction with the less-reactive iron nitride layer and their roles as anti-wear additives.…”