Comparing Wear of Thermoplastic Composites on Steel, Brass, and Aluminum Surfaces

Testing Thermoplastic Composites against Steel

To understand how plastics interact with metals, we conducted controlled tests pairing thermoplastic composites with AISI 1141 cold‑rolled steel counter‑faces. Surprisingly, the smoothest metal finishes (8–12 µin) produced the highest wear on the composites, driven by adhesion‑deformation friction. The 12–16 µin range delivered the lowest wear factors, while 50–70 µin surfaces yielded intermediate values for most composites. Unreinforced formulations behaved differently.

PTFW‑lubricated glass‑fiber‑reinforced polycarbonate was the sole composite that showed increased surface roughness on the steel counter‑face; all other composites reduced surface roughness by up to one‑eighth, while the metal surface consistently roughened across tests.

Wear Behavior

We examined wear behavior of thermoplastic composites against stainless‑steel and brass counter‑faces across two roughness levels. Consistent with expectations, increasing the 304 stainless‑steel surface roughness from 8–16 µin to 50–70 µin raised wear factors for all composites. Interestingly, the corresponding friction coefficients decreased with greater metal roughness.

Wear Factors

Wear factors and friction coefficients were generally higher for 440 stainless steel than for 304. The 440 alloy’s elevated wear likely stems from its lack of work‑hardening during use. When paired with 8–16 µin brass surfaces, wear factors matched those observed with stainless steel, but brass exhibited up to 80‑fold higher wear rates when mated with glass‑ or carbon‑fiber‑reinforced composites. PTFE‑lubricated nylon 6/6 and its aramid‑fiber variant achieved extremely low wear against brass, though in some cases the resulting surface roughness was up to four times greater than that produced on stainless‑steel counterparts.

Aluminum alloy 2024 counter‑faces offered a tighter tolerance window, consistently delivering acceptable wear factors for the composites. The optimum finish was 12–16 µin, yielding the lowest wear.

PTFE

PTFE‑lubricated unreinforced nylon 6/6 and its aramid‑fiber‑reinforced counterpart delivered the lowest wear rates among all aluminum pairings. Nonetheless, wear factors for composites against aluminum remained higher than those observed against steel, stainless steel, or brass. All thermoplastic composites suffered excessive wear on phosphor bronze counter‑faces, except when paired with the two PTFE‑lubricated formulations.

Wear Behavior of Fluoropolymer-Based Composites

Fluoropolymer composites filled with inorganic additives—graphite powder, coke flour, and milled glass fibers—exhibited higher wear against aluminum than steel. Conversely, PTFE composites incorporating bronze and MoS₂ synergistically achieved lower wear on aluminum compared to steel. PTFE composites with organic fillers such as PPS, polyoxybenzoate, and aromatic reinforcing polymer (ARP) showed comparable wear and surface roughness on both metals. Across all fluoropolymer variants, friction coefficients were higher on aluminum than on steel.

Craftech Industries Inc. offers high‑performance, wear‑resistant plastics for a range of industrial applications. Contact us at 1‑800‑833‑5130 to discuss your part requirements.