Wear and micropitting of steel ball sliding against TiN coated steel plate in dry and lubricated conditions

Wear of the steel part sliding against titanium nitride both in lubricated and unlubricated conditions have been investigated. An unexpected micropitting like wear on the steel surface was found in lubricated conditions, after very short run time. Possible wear mechanisms-fatigue, chemical reaction or electrical discharge-are discussed. A special attention is given to electrical discharge mechanism. A remarkable result was obtained when the lubricant, white oil-a good insulator fluid-was replaced with glycerin, an electrical conductive fluid. With glycerin as lubricant no micropitting was observed on the steel surface even after long run time. In unlubricated condition intense, predominant oxidative wear of steel part was found. (c) 2005 Elsevier Ltd. All rights reserved.