DRY SLIDING WEAR AND FRICTION - LASER-TREATED DUCTILE IRON

Pin-on-disc wear and friction of hypereutectic ductile iron, the type employed for automotive components, was investigated at sliding speeds of 5 and 7.5 m s-1, before and after laser surface treatment by CO2 c ontinuous-wave and Nd-YAG pulsed lasers. A significant increase in tra nsition load and wear resistance upon laser treatment has been attribu ted to the ultrafine microstructure and high hardness; laser-melted le deburite was superior to martensite by transformation hardening. Wear rate at a specific contact pressure and sliding speed bears a log-line ar relationship with the harmonic mean of tensile and fatigue stress o f ductile irons. The role of lubrication by graphite during mild wear and plastic deformation in severe wear of pearlitic ductile iron, and its enhanced resistance to plastic flow on laser melting, have been co nfirmed. The coefficient of friction of a ductile iron pin sliding on a steel disc before and after laser melting has been determined and co mpared with that of white iron of identical composition and structure obtained by conventional chilling.