Effect of waviness on the wear behaviour of 080 M40 (EN8) and 817 M40 (EN24A) steels

The effect of waviness was investigated on the wear performance of 080 M40 and 817 M40 steels machined by the turning and surface grinding processes for a sliding wear situation. The wear was measured with a precision relocation technique using a Talysurf 4 and the frictional coefficient force was monitored using a load cell. The worn surface was examined using scanning electron microscopy. For both types of steel, contact was at the wave crests. The crests were progressively truncated and work-hardened during the wear cycle. Generally, friction increased during running-in and stabilized on complete removal of the waves. For dry wear regimes high interfacial temperatures were set up at the wave crests. Consequently, the pin material oxidized and the friction and wear behaviour of the surface altered. On running-in the turned 817 M40 specimens showed large scale redeposition due to adhesive wear at the wave crests whilst the valleys were relatively smooth due to an abrasive process. A white layer of untempered martensite was produced at the surface of the ground 817 M40 specimens. This hard layer initially resisted abrasion and reduced friction.