Improvement in Tribological Properties with Addition of Hexagonal Boron Nitride (h-BN) and Molybdenum Disulfide (MoS₂) Nanoparticles in Aerospace Lubricants

Abstract

In the aircraft mounted accessory gearbox and gas turbine engine gearbox, a significant rise in temperature of lubricant was consistently observed due to the high coefficient of friction (COF) between the moving parts. This phenomenon limits the speed and power transmission of the gearbox. To resolve this, the current study recommends adding specific nanoparticles (NP) as an additive to the military (MIL) grade lubricant to reduce frictional resistance between the gears. Surfactants were also added to hexagonal boron nitride (h-BN) and molybdenum disulfide (MoS₂) nanolubricants (NL) to improve NP suspension. Tribological investigations were conducted with a four-ball tester, a shear stability tester, and a Reichert tester to examine the lubricants. During the four-ball test, the wear scar diameter (WSD) on the specimen decreased by 16.73% and 12.3% with h-BN and MoS₂ NL, respectively, compared to the results obtained using the base lubricant (BL). In the shear stability test, h-BN NL demonstrated 93%, and MoS₂ NL demonstrated 67% more shear stability than the BL, while the COF was reduced by 13% in both h-BN and MoS₂ NLs during the Reichert test. These test results prove that h-BN and MoS₂ NPs, when added to a MIL standard BL, can demonstrate improved tribological capabilities even at extreme operational conditions.

Keywords:

• Tribology
• nanoadditives
• h-BN
• MoS₂
• lubricant
• aerospace

Acknowledgement

The authors would like to acknowledge and thank Aeronautical Development Agency, Bangalore, Ministry of Defence, Government of India for allowing publication of this paper. The authors appreciate CSIR - National Aerospace Laboratories, Bangalore for the support provided for conducting experiments.

Disclosure statement

No potential conflict of interest was reported by the author(s).