A comparative study on the tribological behaviors of nitrided and sulfur-nitrided 35CrMo steel lubricated in PAO base oil with MoDTC additive

Investigation of the Tribological and Tribochemical Interactions of Different Ferrous Layers Applied to Nitride Surfaces

“…With the sulphur nitrided sample EDX (Figure 15) showed a strong presence of iron and sulphur outside the worn area of the pin relating to the presence of a FeS layer after treatment. Within the worn area a higher presence of iron and sulphur is detected possibly indicating the formation and presence of FeS within the contact areas, similar to that observed by Yue et al [3] and Liu et al [17]. Interestingly also present in the worn area is phosphorous and zinc indicating a protective phosphate tribofilm is also present within the wear area.…”

“…Surface engineering techniques have been quickly developed for improving the tribological behaviours and lengthening the service life of machine parts. Among them, salt bath nitriding and sulphur-nitriding are effective and widely used surface treatment techniques in industry [3].…”

“…The presence of sulphur within the treatment bath stabilises the formation of primarily ε-phase within the compound layer and a very shallow finely porous zone [12]. An iron sulphide layer is a good solid lubrication film that shows significant frictionreducing and anti-scuffing properties, but the thin solid lubrication film can be quickly worn away if the substrate is not hard enough to support it [3].…”

“…The selection of lubricating oil and additives is potentially another important problem for improving the tribological properties of key machine parts [3]. There has been little research carried out on the tribochemical interactions between the layers deposited upon nitrided steel surfaces and the additives within the lubricating hydraulic oil.…”

Humic acid: A Biodegradable Organocatalyst for Solvent‐free Synthesis of Bis(indolyl)methanes, Bis(pyrazolyl)methanes, Bis‐coumarins and Bis‐lawsones

“… [20] The widely used protocol to design this important molecule is very straightforward and it can easily obtained by the reaction between aldehydes and indole following the Friedel‐Craft alkylation type pathway. A few protocols are reported in literature using various catalyst and solvent such as enzymes, [21] meglumine, [22] thiamine hydrochloride, [23] graphene oxide, [24] ethyl lactate, [25] sulphated polyborate, [26] Lewis acids, [27–32] Brønsted acids, [33] heteropoly acids, [34–36] solid acids, [37–42] ionic liquids, [43] metal complexes, [44–46] 4‐sulfophthalic acid [47] and Iodine/tert‐Butyl Hydroperoxide [48] . Recently, a number of methodologies have been developed in this field [49–68] .…”