Soot–additive interactions in engine oils

Abstract

Soot is known to cause engine wear. In this work, we focus on how engine oil formulation affects sootrelated wear, and how the lubricant-derived anti-wear fi lm changes when soot is present. Friction and wear experiments of fully and partially formulated diesel engine oils (containing basestock, dispersants and viscosity modifi ers) are conducted with a ball-on-disk rig in the presence of carbon black (CB) as a soot surrogate. The friction coeffi cient was largely unaffected by CB dispersed in the oils, but electrically insulating fi lm formation, an indication of the formation of anti-wear fi lms, was decreased. Wear on the disk was found to either remain the same or decrease when CB was present, depending on the oil formulation. An examination of the lubricant-derived fi lms using Raman and Auger electron spectroscopies found that the presence of more abundant amorphous carbon and lesser amounts of anti-wear fi lm components on the surface was associated with higher wear.

Surface Analysis of Chain Joint Components after Tribological Load and Usage of Antiwear Additives

“…When adding carbon black to the PAO + additive, the friction coefficient is increased to 0,136-0,140. This behavior has also been observed by Uy et al [13,16]. The resulting friction coefficients at the end of further test runs with the same parameters showed the same trend and were always in the range which is established by Figure 11 the size of the worn area on pin and bush is measured and compared, which is shown in Figure 12.…”

“…The carbon black was an industrial carbon black with an average primary particle size of 27 nm. It was added to simulate the presence of soot in used engine oils which is an approach that has already been used by different researchers [13,14]. With this approach, the differences between varying types of carbon blacks and between carbon black and soot have to be taken into account when interpreting the results, which is shown by Dilbat et al [15].…”

Friction and wear mechanisms in boundary lubricated oxy-nitrided treated samples

“…Iron sulphides are formed as 12 part of extreme pressure reaction of the additive, present at critical spots of high stress [6]. 13 There have been very few studies that investigate the interaction of iron oxide layers formed on a 14 nitrided surface with ZDDP. This paper focusses on tribological and tribochemical interactions 15 occurring between a modified steel surface and a fully-formulated hydraulic oil using tribometer tests, 16 supported by chemical analysis to identify the mechanisms of low friction and wear behaviour.…”

“…5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 In the images where the tribofilms were identified two dominant layers were observed. In each 14 image the top layer is the tribofilm followed by the steel substrate underneath. A thicker 15 non-uniform film was found to be formed on the plain sample which had the lowest surface …”

“…13 To understand the formation of the ZDDP tribofilm, the phosphate glass can be characterized. 14 The glass polymerization number (n) can be calculated using the (bridging oxygen) BO (P-O-P)-to-15 (non-bridging oxygen) NBO (-P=O and P-O-Zn) ratio, Equation (2): 16 17 BO/NBO = (n-1)/2(n+1)…”