Abstract
Inspired by Sir George Beilby's research on polished surfaces in the 1920's, continuing progress in microscopy and surface probes has furthered understanding of tribo-formed layers. Known by various names, these highly-deformed and textured layers vary in thickness, defect arrangement, and uniformity. Their nature depends on the type of material being deformed and the type of wear process to which the surface is subjected. Under otherwise similar sliding conditions, different highly-deformed structures form in different materials because of the effects of stacking fault energy, the arrangement of phases, and the partition of frictional work into heat, fracture, and deformation. Third-body deposits originating from adhesive transfer and wear can shield the deformed layers, and the periodic growth and removal of plateaus can result in time-dependent variations in friction and wear. Combinations of tribo-contact modes, like impact with fretting, can also affect the nature of the near surface layers and their attendant effects on wear and friction.