Grey cast iron has been rubbed under dry sliding conditions so that changes in surface topography could be related to subsurface metallurgical changes. 'White layer'forms towards the end of running-in and subse-quently becomes covered with oxide.The presence of free ferrite increases wear, and phosphorus decreases wear during running-in. The use of optical microscopy and stcrcoscan techniques shows that Oplastic: deforma-tion and fracture arc important mcc:hgni~."s of wear during running-in. TE 99 通用摩擦磨損試驗機