LUBRICATED FRETTING WEAR OF A HIGH-STRENGTH EUTECTOID STEEL ROPE WIRE

The fretting wear behaviour of heavily work-hardened eutectoid steel w ire is an important issue in the construction and usage of locked coil steel ropes. These ropes, which are used for high duty applications i n aggressive environments, such as those encountered in the mining ind ustries, can exhibit a variable service life. Earlier papers examined the design features of this class of rope and aspects of the operating regime, which may contribute to this variable life. The as-drawn surf ace of the wire was determined to play a significant role in the frett ing behaviour, initially suppressing wear and friction. In this paper, the influence of low viscosity oils, with and without graphite additi ons, on the fretting behaviour of the as-drawn wire are examined. Oil bath lubrication suppresses effectively wear and friction throughout t he tests. Of greater significance, however, a smear of oil, more typic al of service conditions, is also effective, at least during the early stages of testing. The addition of graphite to this smear of oil aids its retention, and its ability to lubricate and form a shield around the fretting interface. The presence of oil inhibits the ingress of ox ygen and consequently, at higher normal forces, when significant break down of the oil film occurs, micro-welding and tearing of the clean me tal surfaces follows. Even so, wear and friction are still suppressed effectively.