Research on antiwear effect of some additives to grease in fretting process

The results of research on lithium grease with some additives influence on wear prevention in a fretting process are presented in this work. The mild steel couples were tested under dry conditions and lubricated with lithium grease contained additives. As additives there were used: graphite, molybdenum disulphide, Acorox 880 (zinc dioctyldithio phosphate), Molyvan A and Molyvan L in chosen concentrations. Experiments were performed on a laboratory stand FRET-2. In the stand a moving cylindrical specimen of diameter 10 mm and height 2 mm fretted its cylindrical surface against flat surface of stationary specimen. The research tests were performed under normal load 50 N, amplitude of motion 60 |nm and frequency of vibration 200 Hz. A grease seizure load (in four ball test) and consistence were the main features affecting the fretting wear. Graphite and molybdenum disulphide were significantly effective in concentration at least 10%. EP additive (Acorox 880) in concentration more than 1% increased fretting wear. Molyvan A and Molyvan L were not more effective than molybdenum disulphide powder. Lubricating grease at the fretted couple changed significantly the wear mechanism observed on SEM photographs of fretting scars.