Effect of base oil polarity on micro and nanofriction behaviour of base oil + ZDDP solutions

Abstract

Ball-on-disc tribo tests and atomic force microscopy (AFM) were used to analyze the effect of base oil polarity on the friction behaviour of steel-steel contacts lubricated with base oil + zinc dialkyldithiophosphate (ZDDP) solutions. Understanding the lubrication properties of the first chemisorbed layer of additives on work pieces yields important information for the optimization of lubrication in various solutions, in particular with regard to the type of additive and amount needed.To characterize the influence of oil polarity, two reference base oils (hexadecane -non polar and diethylenglycol -polar) were blended with different concentrations of ZDDP-C 4 , and the solutions were tested. A monolayer of base oil/additive solution is deposited on an ASI 52100 steel plate and is scanned on AFM contact mode under several rubbing time and applied load conditions. An AFM technique is developed to estimate microscopic values of friction coefficients showing how the oil polarity contributes to the differences in friction behaviour of the solution due to the addition of ZDDP.

Evolution of ZDDP‐derived reaction layer morphology with rubbing time

“…AFM was previously used to address the nanoscale origins of the effect of base oil polarity on friction and wear behavior of ZDDP‐derived reaction layers (Tomala et al . 2009) using low‐viscosity model base oils. Force vs. distance plots are often used to measure the interaction forces between the tip and the surface, by pushing the tip against the surface, and then separating the tip and surface.…”

Effects of Nanoparticle Enhanced Lubricant Films in Dynamic Properties of Plain Journal Bearings at High Reynolds Numbers

“…Eqs. (5), (6), and (7)) those are hard to find their answer. Limited length mathematical approaches answer are computational overwhelming and costly in the time of calculation [12,17].…”

“…Potassium Tetraborate and Nano boric acid have also been used fruitfully as resistance tumbling additives in oil and greases [5]. Many other solutions [6] and materials [7] have used as lubricant while buyer hearsays advise that the toxicity properties of nano-technology and nano-fluids have not yet been completely discovered [8].…”

The correlation between ZDDP tribofilm morphology and the microstructure of steel

“…Tribofilms developed by ashless AW additives in some cases exhibit resemblance to those formed by ZDDPs and patch-like structures are also sometimes observed [9,10,4]. Such patchiness is generally undesirable since it significantly increases surface roughness, especially for initially smooth surfaces [11,12,13,14,15,1,16,17,18,19] and consequently leads to higher asperity stresses with the associated risk of surface damage. AW additives have been observed to cause an increase in coe cient of friction in mixed lubrication regime [5,20,17,16].…”