Lube-Tech Introduction
Organomolybdenum friction modifiers reduce friction and enhance wear protection in lubricant formulations through the in-situ formation of lubricious molybdenum disulfide tribofilms (MoS2
) [1]. Boron
based antiwear / extreme pressure additives work by reacting with iron oxide surfaces forming a hard borate-iron glassy network [2]. Therefore, lubricant additives based on molybdenum and boron and have been used extensively in traditional drivetrains. The unique benefits and challenges of these additives may present significant opportunities within the electric vehicle (EV) market. Additionally, because of the relative newness of the field, preconceived notions of traditional additive incompatibility with EV requirements may unduly relegate some time-honoured lubricant additives as unusable in EV fluids. This work investigates additive combinations of three traditional organometallic friction and wear modifiers in EV-focused low viscosity fluids. Concerns regarding corrosion, friction, wear, and electrical conductivity are addressed.
Development of new fluids for electric vehicles includes some of the same challenges as with fluids designed for internal combustion engines (ICE), but there are significant differences. First, the average overall operating temperature of a lubricant in a plug-in hybrid engine is lower than that of an ICE, by as much as 25% [3]. In the context of traditional
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.151 page 1
Using conventional molybdenum and boron lubricant additives in electric vehicles
David Boudreau Sr, Research & Development Advisor, Vanderbilt Chemicals LLC
molybdenum and boron additives, which often require a high activation temperature to be functional, lower operating temperatures may pose a significant barrier to the effectiveness of these additives. An additional concern is yellow metal corrosion. In the context of EV, there is a significant increase in the possibility of the lubricating fluid contacting copper components and electronics. As such, the issue of fluid conductivity comes into play in EV-based systems. A high conductivity fluid can promote short circuiting and current leaks. A low conductivity fluid in turn acts as an insulator and/or capacitor. This can result in the build-up of a large charge gradient, which will eventually equilibrate through electrical discharge [4].
For electrical properties, the use of organo-metallic ligand chemistry is in its relative infancy. One element of interest is boron. Boron is a metalloid element possessing both ionic and covalent bonding characters due to the availability of its three electrons in its outer shell. Its presence at interfaces contributes significantly to effective lubrication through two primary mechanisms. The first is through the interaction with oxygen and nitrogen, leading to the formation lubricating compounds like B2
O3 and BN, which
exhibit low friction properties due to their lamellar structure. The second is through the interaction with metals, in particular iron. This results in the creation of a tribofilm consisting of a very hard iron-borate glass network, which serves to reduce wear [2]. As
LUBE MAGAZINE NO.180 APRIL 2024 27
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