Effect of mechanical factors on tribological properties of palm oil methyl ester blended lubricant

The effects of mechanical factors viz. applied load and temperature on the tribological performance of 5% palm oil methyl ester (POME) blended lubricant were studied using a steel-cast iron pair. Wear and frictional measurements were made using a stationary steel ball and a reciprocating cast iron plate in a modified universal wear and friction testing machine. The test conditions were contact pressure, 400 MPa; mean contact velocity, 0.34 m/s; reciprocating stroke, 80 mm; loads, 100-1100 N (fixed temperature); and temperature, 40-140 degrees C (fixed load). Wear scar surfaces were investigated using scanning electron microscopy (SEM) to understand the wear mechanisms involved. Analysis of post bench test lubricating oils was performed using an ISL viscometer and TAN/TBN analyzers to investigate the lubricating oil degradation properties. Results showed that at lower loads (up to 500 N) and temperatures (up to 100 degrees C), the wear rates under 5% POME lubricant are lower, whereas at higher loads and temperatures, the wear rates are higher. The friction behavior of POME as an additive in commercial lubricant indicates the prevalence of the boundary lubrication regime. The viscosity test results showed that 5% POME can improve the viscosity index (VI) properties of mineral-based lubricant up to 500 N load. However, in this investigation, corrosive wear and pits on the damaged surface are the dominant wear mode at higher temperature. (C) 2000 Elsevier Science S.A. All rights reserved.