Mechanisms of fretting wear resistance in terms of material structures for unfilled engineering polymers

Tests were conducted with a GCr15 (E52100, AISI) steel ball fretting against unfilled engineering polymers, including PI, PTFE, PC, PSU, MCPA, POM, ABS, PPS, PA1010, PP, HDPE and UHMWPE. Two types of metallic materials, cast iron HT25−47 and steel 45 (C1045, AISI), were also tested for reference. PI, HDPE and UHMWPE show good performance of fretting wear resistance while PSU results in not only a severe wear on the polymer itself but more serious wear on the steel ball as compared with the metallic materials. The fretting wear resistant properties of unfilled polymers are related to the heat resistance of the materials and the frictional heat produced during fretting, which in turn depend on the molecular chain structure and aggregate state structure of polymers. Further analysis shows that the fretting wear damage behavior on the surface of polymers correspond to their material structures too. According to the topography of the fretting scar and the shape of debris, the polymers tested could be classified into five categories that also have a strong relationship with their own material structures. The results in this paper may give an implication of how to identify the fretting resistant properties of unfilled polymers in terms of their material structures.