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.