Comparison of the tribological behavior of columnar-grained polycrystalline copper with vertical/horizontal orientation sliding against AISI 1045 steel

The unlubricated tribological behavior of columnar-grained polycrystalline copper with vertical orientation (VO) and horizontal orientation (HO) in sliding against AISI 1045 steel is investigated in room air. The friction coefficient and wear rate of HO Cu in sliding against AISI 1045 steel are lower than that of the VO Cu. The friction-induced layers are distinct. The friction-induced layer on HO Cu is composed of metallic Cu, Fe₂O₃, and Fe₃O₄. The wear debris is agglomerated fine particles. The friction-induced layer on VO Cu presents characteristics of plastic deformation and flow. The wear debris is plate-like. The grain orientations and boundaries of VO/HO Cu sample are contributed to the different friction-induced layer and wear mechanism. For VO Cu, the grain boundary perpendicular to the sliding direction makes the slip motion activate difficultly. For HO Cu, the grain boundary parallel to the sliding direction makes the slip motion activate easily.