EFFECT OF DISPERSING LITHIUM GREASE BY CLAY PARTICLES

The present work aims to enhance the lubricating properties of lithium grease by the addition of clay particles as well as paraffin oil. Bearing steel ball loaded and slid on aluminum (Al) sheet was used to test the friction and wear when the contact surfaces was greased by lithium grease dispersed by clay of 30 – 50 μm particles size. Based on the present experiments, it was revealed that dispersing grease by clay particles and blending by paraffin oil decreased friction coefficient. Clay particles decreased the number of the contacting asperities of the two sliding surfaces and consequently friction coefficient decreased. Presence of oil decreased the agglomeration of clay particles, facilitated the rolling of the particles and retarded the sticking of the particles in one of the sliding surfaces. This behavior is attributed to the increased grease fluidity and decreased metallic contact of the sliding surfaces, where the particles were enabled to roll between the two sliding surfaces. Enhancement of wear may be from the ability of particles to work as ball bearing that decreased the formation of the transferred layer form aluminum sheet and separated the two contact surfaces. Clay particles formed protective thin layer on the contact area and provided high carrying capacity and extreme pressure properties. Grease dispersed by 10 wt. % clay content and blended by 10 wt. % oil gave the best wear values.