Unlubricated rolling-sliding wear tests of as-received and electron beam surface melted complex aluminium bronze, CA104, against hardened En19 steel have been carried out. Test samples have been examined using optical microscopy, scanning electron microscopy and microhardness measurements. It is found that both adhesive wear and delamination wear occur in the wear process and the wear debris forms in two ways. Two types of structures exist in the wear debris, which are related to a deformed and a highly deformed subsurface structure in the tested samples. Electron beam surface melting improves the wear resistance of the material but the wear mechanisms involved have not been fundamentally changed.