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In addition, the nanoparticle additive provides in the same IGO formulations strong anti-wear performance as measured by the FE8 test where the wear loss on the discs and rollers was below 10 mg.
Modified ASTM D130 copper strip test (168h@150°C) is improved compared to the fluids without hBN, both in the liquid and vapour phases (see table 2 and 3). These results are surprising, and the underlying mechanism is under investigation using circuit board tests and other evaluations.
Table 1: FE8 wear test (DIN 51819-3) results of different industrial gear oil formulations (12 cSt at 100°C). * Pass the test according to DIN 51819-3; ** Torque accuracy is ± 0.25%. Base fluid: VISCOBASE®
5-220 - API Group III base oil mix. Fully formulated: Base fluid + industrial gear oil additive package
Similar strong performance was observed in rolling contact fatigue, as measured using a micro-pitting rig, where the pitting lifetime of two 3.5 cSt e-drive formulations was extended by the inclusion of the hBN-based additive (Figure 3). All formulations included an e-drive additive package, showing the hBN-additive’s performance complemented an already strong performance (see table 3). This extension of pitting lifetime can help to counteract the additional fatigue stress that equipment will encounter with lower viscosity formulations and is counter to the behaviour of many anti-wear additives, which can significantly decrease pitting lifetime. In a separate set of formulations with a package delivering strong extreme pressure performance, as measured by the Forschungsstelle fuer Zahnraeder und Getriebebau (FZG) scuffing test, the addition of hBN-based additive resulted in an increase of two failure load stages, from 8 to 10 (see table 2).
Figure 3: Pitting test results of 3.5 cSt at 100°C prototype e-driveline fluids (EDF) including an e-driveline additive package with and without 2 wt% hBN-based additive
The importance of these results becomes obvious if they are compared with results of typical anti-wear components such as ZDDP or other sulphur and phosphorous containing anti-wear components. With these components FZG extreme pressure performance can be improved as well, but only by sacrificing copper corrosion rating.
Table 3: Relevant properties of the formulated e-driveline prototype fluids with a comprehensive e-drive DI package used in the MPR pitting test rig. PPD: VISCOPLEX®
1-180 – polymethacrylate based pour point depressant
Table 2: Relevant properties of e-driveline prototype fluids with a low thickening basic e-drive DI package used in the FZG A10/16.6R/90 scuffing test and Cu strip test according to ASTM D130. Antifoam: VISCOPLEX® 14-520
In all hBN-based prototype formulations copper corrosion rating according to the modified ASTM
42 LUBE MAGAZINE NO.176 AUGUST 2023
In many electric drive units, the impact of lubricant electrical properties, such as electrical conductivity and breakdown voltage, must also be considered. The hBN-based additive has minor contribution to the electrical conductivity in fluids even in high concentration since hBN is a non-conductive material.
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