Dry sliding wear of ferrous PM materials

Ashby's map for dry sliding wear of wrought steels has been used as a guide to interpret the dry sliding wear behaviour of PM materials. It has been s hown that this map is useful in understanding the acting wear mechanisms an d also the experimental wear rates. For given tribological conditions, in t erms of normalised pressure and sliding velocity, the sliding wear resistan ce of PM materials is similar to that of wrought steels, although a closer look at the experimental results highlights the peculiar role of porosity a nd of a heterogeneous microstructure. In particular, materials with a poros ity content of about 10% and with an homogeneous microstructure display the best performances. Since mild wear in metals can be obtained through the f ormation of protective oxide glazes, steam treatment turned out to be a nat ural way of increasing the sliding wear resistance of PM ferrous materials. The 'surface durability' of steam treated materials was thus shown to depe nd on the quality of the layer, the applied load and the nature of the coun terface. The role of the counterface and the opportunity to adopt other sur face treatments to increase the sliding wear resistance of PM ferrous mater ials are also discussed. (C) 2001 IoM Communications Ltd.