Sliding wear of copper against alumina

OFHC copper pins with 10 ppm oxygen were slid against alumina at a load of 50 N and sliding speeds of 0.1 ms(-1) to 4.0 ms(-1) The wear characteristic s of copper were related to the strain rate response of copper under uniaxi al compression between strain rates of 0.1 s(-1) and 100 s(-1) and temperat ures in the range of 298 K to 673 K. It is seen that copper undergoes flow banding at strain rates of 1 s(-1) up to a temperature of 523 K, which is t he major instability in the region tested. These flow bands are regions of crack nucleation. The strain rates and temperatures existing in the subsurf ace of copper slid against alumina are estimated and superimposed on the st rain rate response map of copper. The superposition shows that the subsurfa ce of copper slid at low velocities is likely to exhibit flow band instabil ity induced cracking. It is suggested that this is the,reason for the obser ved high wear rate at low velocities. The subsurface deformation with incre asing velocity becomes more homogeneous. This reduces the wear rate. At vel ocities >2 ms(-1) there is homogenous flow and extrusion of thin (10 mu m) bands of material out of the trailing edge. This results in the gradual inc rease of wear rate with increasing velocity above 2.0 ms(-1).