Direct observation of frictional seizure of mild steel sliding on aluminum by X-ray imaging - Part II - Mechanism

Observation of frictional contacts has always been a problem for long as the contact is normally hidden. In this work, we have used an X-ray microscope for in-situ observation of frictional seizure, wear and interfacial features during the testing of mild steel specimens sliding against Al 6061 disk. This technique enables the observation of interfacial features of the hidden contact. Seizure tests were conducted at different sliding speeds of 2, 4 and 5 m/s. The images obtained during the tests indicated that the wear process was a combination of random transfer events and cyclic process of a close contact followed by a partial separation of the sliding surfaces. Wear was concentrated over a certain specific area during the initial part of the test but later the contact developed into a conformal contact following a lumpy transfer of material. The mechanisms of seizure and wear were affected by the sliding speed. At a sliding speed of 4 and 5 m/s, the transfer and bonding of material was not directly caused by nascent surface contact but due to contact of rolled and compacted wear debris with the nascent surfaces. Whereas at lower sliding speed (2 m/s) the transfer and bonding of deposits occurred due to direct contact of nascent sliding surfaces. (C) 2000 Kluwer Academic Publishers.