Utilization of the focus variation method for determining the wear volume in the pin-on-disk sliding test

The measurement of wear volume in tribological tests is a critical step in wear characterization. There are many methods and instruments for wear volume measurement reported in the literature and most of them have already been commercialized. These commonly determine wear volume by means of tactile or optical methods, requiring costly and/or specifically developed instruments. In this study, an alternative method for determining wear volume, obtained after a sliding test with a pin-on-disk type apparatus, using focus variation microscopy is reported. A reflective-type light microscope, equipped with a digital camera, together with a range of computer software was used for the line profiling of wear scars, rather than a specialized focus variation microscope. In this study the relatively "shallow" depth of field at the high magnification of the light microscope was precisely used for determining surface line profiles on both slightly and heavily worn specimen surfaces after a series of tribological wear tests. Results of the study method were compared with both profilometric measurements obtained from a 3D optical microscope and with those obtained using a previously reported method. This comparison showed that the method under development and tested in this study yielded successful measurements, comparable to those obtained using the much more expensive 3D optical microscope.