In situ Acoustic Emission for wear life detection of DLC coatings during slip-rolling friction

Different diamond-like carbon (DLC) coatings on a steel substrate (100Cr6) were tested under slip-rolling friction conditions against uncoated counter bodies of the same steel. The initial maximum Hertzian pressure was varied in a range of P0 = 1.5–2.3 GPa. The friction tests were carried out under dry conditions and with an unadditivated paraffin oil as lubricant. It could be shown that the thickness of the coatings affects the respective wear life. Further, a very important factor for the wear life of a coating under lubricated slip-rolling conditions is the roughness of the surface of the respective counterbody. The wear life tests were monitored by recording in situ the Acoustic Emission (AE) signals. Some causes for a high AE activity could be identified.