Preliminary investigations on the tribological performance of hexagonal boron nitride nanofluids as lubricant for steel/steel friction pairs

Abstract

With laminated structure like graphite, hexagonal boron nitride nanoparticle (nano-hBN) performed excellent anti-wear and friction-reducing properties. In this paper, hBN nanofluids were prepared using sodium polyacrylate (PAAS) as dispersant in water. Four-ball tribometer and pin-on-disk tribometer were employed to evaluate the tribological performance and lubrication behavior of the above-prepared lubricating fluids during steel/steel friction. The worn surface of balls and disks was analyzed by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and x-ray photoelectron spectrometer (XPS). The minimum lubricating film thickness was calculated by Hamrock and Dowson equation. Results showed that 0.7 wt% was the optimum concentration of nano-hBN in water which significantly reduced the coefficient of friction (COF) and wear scar diameter (WSD) by about 29% and 15%, respectively. The lubricating film thickness was lower than both nanoparticles diameter and worn surface roughness. From the above it was concluded that the worn area could be divided into direct contact, particle lubricating and liquid lubricating area with rolling mehanism, interlayer sliding mechansim, polishing mechansim and mending mechansim of nanoparticles. A protective film was formed on friction surface by PAAS molecule, FeOOH and FeO due to the absorption effect and tribochemical reaction between the nanofluids and worn surface, which further reduced the friction and wear rate.

Effects of hexagonal boron nitride based nanofluid on the tribological and performance, emission characteristics of a diesel engine: An experimental study

“…The results showed the reduction in the COF and wear scar diameter by 35.7% and 35.2% respectively because of the formation of tribolayer on the counterpart surfaces. He et al 39 examined the tribological performance of hBN nanofluids by utilizing four‐ball and pin‐on‐disc tribotesting machines. The reduction in friction coefficient and wear scar diameter was observed by as much 29% and 15%, respectively, using hBN based nanofluid.…”

Lubrication mechanisms of hexagonal boron nitride nano-additives water-based lubricant for steel–steel contact

“…22 hBN is a cheap lubricant that has better biodegradability and exhibits superior tribological properties upon mixing with conventional engine oils 15,16 or vegetable oils 17–19 or water. 20…”

“…Among nanoparticle-based lubricants, hexagonal boron nitride (hBN) is a substance being studied with increasing interest. [15][16][17][18][19][20] hBN exhibits a laminated structure with an ultra-flat surface like graphite. Strong covalent boron-nitrogen bonds form the layer; weak Van der Waals force exists between layers.…”

“…22 hBN is a cheap lubricant that has better biodegradability and exhibits superior tribological properties upon mixing with conventional engine oils 15,16 or vegetable oils [17][18][19] or water. 20 Several mechanisms have been proposed to explain how nanolubricants improve lubrication; some of these include protective film creation, rolling effects, mending, and polishing effects. Rolling effects refer to the nanoparticles acting as ball bearings against rubbing surfaces during processes like sliding or ploughing.…”

A Comprehensive Review of Water-Based Nanolubricants

“…The results showed that the nanofluid with SDS had 4-5 days stability while without SDS the NPs agglomerated within 1 h after preparation. [116], polydopamine (PDA) [118], sodium dodecyl sulfate (SDS) [124,125], polyvinylpyrrolidone (PVP) [119], Igepal CO-520 [117], cetrimonium bromide (CTAB), and sodium dodecylbenzene sulfonate (SDBS) [119,184] Others dialkyl polyoxyethylene glycol thiophosphate ester (DTP-10, DTP-20) [154], oleylamine [93] benzalkonium chloride [90], sodium polyacrylate (PAAS) [159], SHMP (sodium hexametaphosphate), 1,4-butylene glycol [203], coconut diethanol amide (CDEA) [204]…”