Study on Tribological Behavior of PG-2 Gear Oil Additive Package

The PG-2 gear oil additive package with similar composition and structure as that of foreign commercial counterpart Hitec 343 was developed. The chemical structure of the developed gear oil additive package was analyzed by means of infrared spectroscopy, while its thermal stability examined by means of thermogravimetric analysis. The antiwear and extreme pressure properties of the PG-2 additive package as an additive in hydrogenated 80W/90 base stock were comparatively investigated on four-ball machines, using the Hitec 343 as a control. The worn steel surface morphologies were observed on a scanning electron microscope, and the elemental distributions thereon were determined on an energy dispersive spectrometer (EDS). It was found that the PG-2 package had good thermal stability and comprehensive properties (anti-wear, antirust, anticorrosion, and thermal stability) comparable to that of the commercial gear oil additive package Hitec 343, and the former had much better extreme pressure properties than the latter, which could be attributed to the stronger tribochemical interaction of the PG-2 additive with the rubbing steel surface. The worn steel surface lubricated with the hydrogenated 80W/90 oil containing Hitec 343 was characterized by mild scuffing, that lubricated with the base stock containing the PG-2 additive by mild adhesion wear and scuffing. Higher contents of S and P were detected by EDS on the worn steel surface lubricated by 80W/90 containing PG-2, which could account for the much better extreme pressure properties of the PG-2 additive than the Hitec 343 counterpart. With a view to the excellent comprehensive properties of the PG-2 additive package, it could be rational to anticipate that PG-2 would find promising industrial application as a novel high-performance gear oil additive.