Improving The Tribological Characteristics of In-House Made Acid-Activated Iraqi Bentonite Lubricating Greases Using Graphite and Polytetrafluoroethylene Nanoplatelets as Additives

Traditional soap-based greases such as lithium and calcium are no longer able to meet the requirements of high-performance lubrication due to their high cost and environmentally harmful nature, thus there is a need for new solid, non-organic and non-soapy greases that can act as effective and inexpensive greases. This paper presents a comparative study and analysis of the effect of adding polytetrafluoroethylene (PTFE) and graphite to Iraqi Bentonite Lubricating Greases Activated with Nitric Acid (AIBLG-HNO3) of which 24-types were synthesized in laboratory using two types of local base oil stock 60 and 150, Iraqi bentonite as thickener, and two types of soft and hard paraffin waxes. The tribological characteristics such as corrosion resistance and diameter of wear scars (WSDs) that take place due to friction between metal surfaces inside the equipment were studied, as WSDs are directly proportional to friction. The results showed that the manufactured Iraqi bentonite greases have a high ability to resist corrosion or anti-wear, especially when adding PTFE to all samples. It was concluded that adding either PTFE or graphite nanocomposites should be preferably at a weight percentage of not less than 15 wt%. Moreover, in comparison with the parent Iraqi Bentonite Lubricating Greases (IBLG) samples free of additives, the results also indicate a decrease in WSDs by 90% to 93% using base oil 150 for four samples and in the presence of either soft and/or hard wax.