Tribological performances of UHMWPE and PEEK under dry sliding conditions against steel and various polyetherimide polymer counterfaces

Purpose This study aims to investigate and compare the tribological behavior of two high-performance polymers, ultra-high-molecular weight polyethylene (UHMWPE) and polyetheretherketone (PEEK), under dry sliding conditions against steel and various polyetherimide (PEI)-based polymer counterfaces. Design/methodology/approach Pin-on-disk wear tests were carried out using the UHMWPE and PEEK pins sliding against four different counterfaces of general purposed (GP)-PEI, wear resistant (WR)-PEI, glass fiber-reinforced PEI (PEI + 20% GFR) and AISI 304 L stainless steel. The experiments were conducted under normal loads of 20, 40 and 60 N at a constant sliding speed and distance. The coefficient of friction (COF), specific wear rate (SWR) and dominant wear mechanisms were evaluated based on the experimental measurements and optical microscopy observations. Findings The UHMWPE consistently exhibited lower COF and specific wear rate values than those of the PEEK, under all test conditions. Its best tribological performance was achieved at a load of 60 N against the GP-PEI counterface, yielding the COF and SWR values of 0.0728 and 7.96 × 10–15 m²/N, respectively. For the PEEK, the optimum values of the COF and SWR were obtained as 0.1856 and 8.79 × 10–15 m²/N, respectively also against the GP-PEI. The superior performance of the UHMWPE was mainly attributed to its self-lubricating behavior and the formation of a stable transfer film. However, the PEEK exhibited higher and more unstable friction behavior, particularly when sliding against the PEI + 20% GFR and steel counterfaces. Originality/value Unlike most previous studies focusing primarily on the metal–polymer tribological pairs, this study provides a comprehensive comparative evaluation of polymer–polymer and polymer–metal interfaces. The findings demonstrate that the UHMWPE outperforms the PEEK in the dry sliding applications and offer valuable insights for the rational selection of tribo-pairs in the engineering applications.