🧪 PEEK
PEEK Machined Components for Duluth, MN Mining, Marine, and Heavy Equipment
Polyether ether ketone occupies a narrow but critical specification space in Duluth's industrial supply chain: it goes where metal is too heavy or too corrosive and where standard engineering plastics lack the thermal stability or mechanical strength to survive. In the ore processing facilities of Minnesota's Iron Range and the pump rooms and bearing assemblies of Great Lakes vessels, PEEK components are solving problems that stainless steel creates (galvanic corrosion, galling, excessive weight) and that nylon or acetal can't solve (continuous service above 100°C, concentrated acid wash exposure, sustained bearing loads above 0.3 MPa). ManufacturingBase connects Duluth buyers with precision PEEK machining suppliers who understand the material's processing requirements and can hold the tolerances that bearing and sealing applications demand.
ISO 9001AS9100ISO 13485
Unfilled PEEK in Fluid Handling and Bearing Applications
Unfilled PEEK — semicrystalline polymer, density 1.32 g/cm³, continuous service temperature 250°C — is the baseline specification for components where chemical resistance and thermal performance are primary drivers and dimensional precision is critical. In slurry pump applications common to Iron Range taconite processing, PEEK wear rings and throat bushings outperform bronze in acidic iron slurry environments (pH 3.5-6.5, iron sulfate concentration) where bronze corrodes rapidly and releases metal ions that contaminate process water. PEEK's chemical resistance spans sulfuric acid up to 30 percent concentration, hydrochloric acid, and hydrofluoric acid at limited concentrations — the chemical exposure profile of mineral processing operations.
Machined unfilled PEEK holds tolerances of ±0.025 mm on bores and diameters with proper tooling and temperature-controlled inspection. Its low coefficient of friction against steel (0.35-0.45 µk dry) and good PV rating (0.06 MPa·m/s continuous) make it a practical bearing material in lightly lubricated or dry-running applications. For Duluth marine applications — stern tube bearing wear rings, water-lubricated strut bearings, sea water pump impeller sleeves — PEEK's water absorption of only 0.5 percent (versus 1.5-3 percent for nylon) maintains dimensional stability in constant water immersion, which is a real engineering advantage when diametral clearances of 0.05-0.10 mm determine pump efficiency.
PEEK billet for machining is available in natural (tan/beige), which indicates unfilled virgin resin, and in black, which typically indicates a compounded grade — buyers should confirm grade and filler content from the supplier's material certification before specifying 'unfilled PEEK' and accepting a black-pigmented part. Color alone does not guarantee grade; request Victrex, Solvay Ketaspire, or equivalent manufacturer's certificate of conformance with each order.
Glass-Filled PEEK for Structural Load-Bearing Components
30 percent glass-filled PEEK raises flexural modulus from 3.6 GPa (unfilled) to approximately 10 GPa — close to aluminum — while increasing compressive strength from 120 MPa to 160 MPa. The stiffness increase makes glass-filled PEEK (GF-30 PEEK) the grade of choice for structural brackets, bushings under high radial load, and housings where dimensional stability under sustained load matters more than friction properties. For Duluth mining equipment conveyor components — guide blocks, chain slider bars, support pads — GF-30 PEEK's combination of stiffness, temperature resistance, and chemical inertness eliminates the periodic replacement cycle that acetal and nylon components require in abrasive slurry environments.
The trade-off with glass fill is tribological performance: the glass fibers, while increasing strength, abrade mating metal surfaces when used as a bearing material against soft substrates. GF-30 PEEK should not be specified as a bearing material against polished aluminum shafts — it will score the aluminum. Against hardened steel (58 HRC minimum) or stainless steel, glass-filled PEEK performs acceptably in moderate PV applications. For pure bearing applications, unfilled PEEK or carbon-filled PEEK is the better grade.
Machining GF-30 PEEK requires carbide tooling — glass fiber rapidly dulls HSS — and positive rake angles to minimize heat generation. The glass fiber's abrasiveness means tool changes are more frequent than for unfilled PEEK, and shops must account for this in quoting precision components. Duluth shops with experience in glass-filled composites and ceramic materials adapt most readily to GF-30 PEEK machining protocols.
Carbon-Filled PEEK for Self-Lubricating Bearing and Seal Components
30 percent carbon-fiber-filled PEEK combines the base polymer's thermal and chemical resistance with dramatically improved tribological properties. Carbon fiber fill reduces the dry coefficient of friction against steel to 0.15-0.20, compared to 0.35-0.45 for unfilled PEEK, and raises the continuous PV rating to 0.12-0.18 MPa·m/s — two to three times unfilled PEEK. For Duluth applications in mining equipment and marine machinery where lubrication access is difficult or where lubricant contamination of process fluids is prohibited, CF-30 PEEK delivers the bearing performance of a lubricated bronze bushing without any lubricant.
Electrical conductivity is a secondary benefit of carbon fill — CF-30 PEEK's resistivity drops to 10^2-10^4 Ω·cm from unfilled PEEK's 10^16 Ω·cm, which dissipates static charge buildup in powder handling and fuel transfer applications. For Iron Range iron ore pellet handling conveyor systems where electrostatic charge on dry pellets creates discharge hazards, CF-30 PEEK slider bars and guide components address both the wear and the static issues simultaneously.
Dimensional stability of CF-30 PEEK exceeds both unfilled and glass-filled grades because carbon fiber reduces the coefficient of thermal expansion to approximately 14 µm/m·°C (versus 50 µm/m·°C for unfilled PEEK). This lower CTE makes CF-30 PEEK the preferred grade for precision bearing fits and seal components where thermal cycling — from Duluth's -30°C winter to operational temperatures of 150-200°C — would otherwise open critical clearances. When designing press-fit or transition-fit PEEK components for steel housings, the CTE mismatch between PEEK and steel must be calculated across the full service temperature range to ensure the fit remains functional at temperature extremes.
Frequently Asked Questions
For slurry pump wear rings contacting acidic iron ore slurry, unfilled PEEK is the baseline specification because chemical resistance is the primary driver — glass and carbon fillers do not improve chemical resistance and in some aggressive chemistries can provide pathways for chemical ingress at the fiber-matrix interface. Unfilled PEEK withstands iron sulfate slurry at pH 3.5-6.5, dilute sulfuric acid up to 30 percent, and iron chloride solutions — the typical chemical environment of magnetite processing. The caveat is wear rate: unfilled PEEK in a highly abrasive slurry (taconite fines at 150-300 mesh) wears faster than a filled grade. The practical solution is to oversize initial clearance slightly (0.15-0.20 mm diametral vs. the typical 0.05-0.10 mm for a metal ring) to account for controlled wear-in, and to establish a replacement interval based on pump efficiency monitoring rather than fixed maintenance schedule. If abrasion wear dominates over chemical attack in your specific slurry, carbon-filled PEEK's improved hardness (relative to unfilled) can extend wear ring life 30-50 percent with acceptable chemical resistance tradeoff.
Lake Superior vessel pump rooms experience significant thermal cycling: ambient temperatures from -25°C in winter port calls to 40-50°C in enclosed operating spaces during summer, with process fluid temperatures ranging from near-freezing sea water intake to 80-120°C in heat exchanger service. PEEK's continuous service temperature of 250°C (unfilled) provides substantial margin above any realistic pump room operating temperature. The more relevant design concern is dimensional change across the -25°C to 120°C service range. Unfilled PEEK has a CTE of approximately 50 µm/m·°C, meaning a 100 mm diameter bearing ring grows 0.50 mm diametrally across a 100°C temperature rise — a 0.50 mm change that must be designed into the fit specification. Carbon-filled PEEK's lower CTE (14 µm/m·°C) reduces this to 0.14 mm over the same range, which is why CF-30 PEEK is preferred for precision bearing fits on Lake Superior vessels. PEEK's water absorption of 0.5 percent in continuous water immersion is stable and causes only minor dimensional change — approximately 0.015 mm per 100 mm — well within bearing clearance design margins for sea water-lubricated applications.
PEEK's chemical resistance makes it compatible with most industrial cleaning regimes used in food-grade mining equipment and processing facilities. It withstands steam sterilization at 134°C in autoclave cycles (the standard pharmaceutical validation temperature), which also covers the steam cleaning protocols used in food-adjacent mineral processing. PEEK resists CIP (clean-in-place) chemical cycles including sodium hydroxide up to 30 percent concentration, phosphoric acid-based cleaners, and peracetic acid sanitizers at use concentrations. The material complies with FDA 21 CFR 177.2415 for repeated food contact when compounded with food-grade additives — verify that the specific grade and colorant used is covered by the supplier's FDA compliance documentation, as compounded grades with non-food-grade additives may not qualify. For potash and specialty mineral processing in the Iron Range region where contact with food ingredients downstream is a compliance consideration, unfilled PEEK with documented FDA compliance letter is the specification to request.
PEEK machines with dimensional precision approaching aluminum on properly equipped CNC equipment. Standard achievable tolerances for bored housings and turned shafts in PEEK are ±0.025 mm (±0.001 inch), with careful shops achieving ±0.013 mm on critical diameters using sharp tooling, light finish passes at low feed rates, and temperature-compensated inspection. PEEK's stress relaxation behavior requires attention: the material creeps under sustained clamping or cutting force, so aggressive roughing cuts should be followed by a rest period before finish machining to allow stress relief. For bearing bore work, boring to within 0.1 mm in rough, allowing 30-minute relaxation, then finishing to dimension reduces spring-back error. PEEK's low thermal conductivity (0.25 W/m·K) means heat from cutting accumulates in the part — air blast or light mist cooling prevents thermal growth that would otherwise cause bore-size drift across a production run. Shops experienced in PTFE and other semi-crystalline thermoplastics adapt quickly to PEEK's machining characteristics.
PEEK billet rod costs $150-400 per kilogram depending on grade and diameter — versus $8-15/kg for 316 stainless steel, $6-10/kg for 6061 aluminum, and $25-60/kg for titanium Grade 5. On a raw material basis, PEEK is expensive. The economic justification comes from total cost of ownership. In corrosive slurry applications where 316 stainless wear rings last 500-800 hours before replacement, PEEK wear rings regularly achieve 1,500-2,500 hours — a 2-3x service life improvement that more than offsets the material premium when you account for labor, downtime, and inventory carrying cost of replacement parts. PEEK's 1.32 g/cm³ density means a PEEK component weighs roughly 17 percent of an equivalent-volume steel component — reducing installation cost and the load on supporting structure in marine applications. For Duluth procurement teams evaluating PEEK versus metal, the analysis should include maintenance labor rate (which is high in union shipyard and mining environments), production downtime cost per hour, and number of annual replacements, not just part price.
Last updated: July 2026
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