Title Steady-state dry friction and subsurface thermal response of neat and hybrid PEEK sliding against 42CrMo4+QT steel
Authors Kačinskas, Tomas ; Baskutis, Saulius ; Grigaliūnas, Valdas
DOI 10.3390/coatings16091012
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Is Part of Coatings.. Basel : MDPI. 2026, vol. 16, iss. 9, art. no. 1012, p. 1-27.. ISSN 2079-6412
Keywords [eng] polyether ether ketone (PEEK) ; hybrid PEEK ; dry sliding ; coefficient of friction ; subsurface temperature ; ring-on-block test ; polymer–steel contact ; surface heterogeneity
Abstract [eng] Bearing-grade PEEK composites are intended to improve sliding performance, but filler addition does not necessarily reduce friction. This study compared the dry sliding tribological behaviour of neat PEEK and hybrid PEEK containing PTFE, graphite, and carbon fibre against 42CrMo4+QT steel. Ring-on-block tests were performed at nominal PV values of 0.3–3.2 MPa·m/s, contact pressures of 0.87–5.82 MPa, and sliding velocities of 0.26–0.55 m/s. Each material–condition combination was tested using three independent specimens. Coefficient of friction was calculated from simultaneously measured tangential and normal forces, and subsurface temperature was recorded continuously. Initial and post-test surfaces were examined using optical and extended depth-of-field microscopy. Group mean COF values ranged from 0.052 to 0.123. Hybrid PEEK exhibited a higher numerical mean COF than neat PEEK in all six operating conditions, with relative differences of approximately 1.53–8.36%. Two-factor ANOVA estimated an overall hybrid-minus-neat difference of +0.003388 COF units (95% CI 0.001279–0.005496; p = 0.0029), whereas none of the six condition-specific neat–hybrid comparisons was significant after Holm correction. Initial temperature, maximum temperature, and baseline-normalised temperature rise were reported for every specimen and treated descriptively. Both materials reached stable sliding states without seizure or uncontrolled thermal escalation. Post-test EDF observations showed a denser pattern of fine grooves on neat PEEK, whereas hybrid PEEK exhibited comparatively smoother intervening regions interrupted by fewer but locally deeper features. Mass changes remained close to the capability of the applied balance and did not permit quantitative wear-rate comparison. The results show that the investigated hybrid formulation did not provide a dry-friction reduction advantage over neat PEEK under the tested conditions.
Published Basel : MDPI
Type Journal article
Language English
Publication date 2026
CC license CC license description