Bearing Grade vs CF30 PEEK: Which Is Better for Wear?

Content Menu

● Quick Comparison: CF30 vs Bearing-Grade PEEK

● What Does the Published Test Data Show?

● Friction Coefficient: CF30 vs Bearing Grade

● Specific Wear Rate

● Limiting PV: What the Published Data Shows

● Why the Two Grades Behave Differently

● When to Choose CF30 PEEK

● When to Choose Bearing-Grade PEEK

● How to Select Between CF30 and Bearing Grade

● Temperature Can Change the Result

● Can Victrex Data Be Used to Specify PRES PEEK?

● Frequently Asked Questions

>> Data Sources

>> Related Articles

Bearing-grade PEEK is generally the better starting point for continuous dry-sliding applications where low friction and wear resistance are the primary requirements. CF30 PEEK is often preferred when structural stiffness, dimensional stability, and load-bearing capability matter more. Neither grade is universally better for wear: tribological performance depends on PV, temperature, counter-face material, surface finish, lubrication, and the specific formulation. Under the published test data discussed below, the friction coefficient of CF30 PEEK climbs from ~0.26 to ~0.66 (+154%) as PV rises from 5 to 15 MPa·m/s — while a bearing-grade formulation falls from ~0.42 to ~0.34 (-19%).

CF30 PEEK vs Bearing-Grade PEEK: Quick Comparison

Simple selection rule: if the part slides continuously without lubrication, start with bearing grade; if the part primarily carries structural load and slides only occasionally or at low PV, start with CF30.

Is CF30 PEEK Better Than Bearing-Grade PEEK for Wear?

The key engineering point is that CF30 PEEK and bearing-grade PEEK are optimized for different purposes. CF30 relies primarily on carbon-fiber reinforcement to improve stiffness, strength, dimensional stability, and wear behavior. Bearing-grade PEEK typically combines reinforcement with solid lubricants such as PTFE and graphite to reduce friction and improve dry-sliding performance.

CF30 PEEK can provide good wear performance, particularly under low to moderate PV conditions, while offering substantially higher stiffness and strength than most bearing-grade formulations. For this reason, carbon-fiber reinforcement alone should not automatically be treated as a substitute for a dedicated bearing-grade formulation.

What Does the Published Test Data Show?

The comparison below draws on published tribological data for Victrex grades. The comparison uses:

Friction Coefficient: CF30 vs Bearing Grade

The important observation is not simply which material has the lower friction coefficient at one operating point — it is the change in friction behavior as PV increases. Under the published test conditions:

• 450CA30 starts with a lower friction coefficient at PV 5 — at PV 15, its friction coefficient increases substantially;

• 450FC30 starts higher but decreases under the higher-speed, higher-pressure condition.

What does this mean for engineers? A material that performs well at low PV may not remain the best choice as pressure and sliding speed increase. For applications with increasing PV, the complete formulation and tribological system should be evaluated rather than selecting a grade based only on fiber reinforcement.

Specific Wear Rate

Under the published test conditions, 450FC30 shows approximately one-third the specific wear rate of 450CA30. The CA30 wear rate remains relatively high and approximately flat across the two reported conditions, while the bearing-grade formulation shows substantially lower wear.

This supports a practical distinction:

• CF30: useful when structural performance and moderate tribological duty must be combined;

• Bearing grade: more appropriate when minimizing friction and wear is the primary objective.

Limiting PV: What the Published Data Shows

The limiting PV (Lpv) is the pressure×velocity condition at which excessive wear, interfacial melting, or severe scoring occurs under the specified test method. Published values include:

These values are test results for the specified grades and test configuration, not universal continuous-service ratings. (*Grade designations as published in the Victrex PEEK Properties Guide —verify exact designations against the current edition before referencing them in specifications.)

Why Can Bearing-Grade PEEK Behave Differently from CF30?

CF30 PEEK

Carbon fiber primarily provides reinforcement: stiffness, strength, and dimensional stability. It also contributes to wear behavior through load sharing and transfer-film formation — but fiber alone does not provide the same lubricating effect as a formulation containing dedicated solid lubricants.

Bearing-Grade PEEK

Bearing-grade formulations may combine reinforcement with solid lubricants such as PTFE, graphite, and other formulation-specific tribological additives. These additives reduce interfacial shear and help maintain a lubricating transfer film during sliding.

Therefore: carbon fiber primarily helps PEEK carry load and maintain stiffness, while solid lubricants reduce friction and improve tribological behavior. The exact formulation varies by manufacturer and grade, so performance should always be evaluated using grade-specific data.

When Should You Choose CF30 PEEK?

CF30 PEEK is generally the better starting point when the component must combine structural performance with moderate sliding or wear requirements. Consider CF30 when:

• 1. Structural stiffness is important — CF30 provides substantially higher stiffness than unfilled PEEK (flexural modulus 23 GPa vs 3.8 GPa) and can be advantageous when deformation must be minimized.

• 2. The component carries significant mechanical load — the PRES reference data cited in this article gives CF30 a tensile strength of approximately 250 MPa, compared with approximately 140 MPa for the referenced bearing-grade formulation.

• 3. Dimensional stability is critical — the PRES CF30 reference data gives a coefficient of thermal expansion of approximately 5 ppm/K(below Tg) and an HDT of approximately 336°C.

• 4. PV is relatively low — under the published test conditions discussed here, CF30 can provide acceptable friction and wear performance at low to moderate PV.

• 5. The part is both structural and tribological — for a structural component that also slides against another surface, CF30 may provide a better balance of stiffness, strength, dimensional stability, and wear performance than a softer tribological formulation.

When Should You Choose Bearing-Grade PEEK?

Bearing-grade PEEK is generally the better starting point when the primary design requirements are:

• Low friction, dry-running capability

• Wear resistance and stable tribological behavior

• Higher PV operation with reduced frictional heat generation

Typical applications include bushings, bearings, wear rings, seal rings, thrust washers, and piston rings — especially where external lubrication is impossible or undesirable.

How to Select Between CF30 and Bearing-Grade PEEK

A practical selection process is:

Step 1 — Calculate PV

For a sliding interface: PV = Contact Pressure × Sliding Velocity. For a cylindrical sliding component: P = Load / (d × L), where P = contact pressure (MPa), d = bearing diameter (mm), L = bearing length (mm). The result is compared against the material's limiting PV with a safety factor.

Step 2 — Check operating temperature

Frictional heating plus process temperature together set the interface temperature — see the temperature reduction table below.

Step 3 — Identify the primary design requirement

Stiffness and load (CF30) vs continuous low-friction dry running (bearing grade).

Step 4 — Evaluate the counter-face

Hardened steel, stainless steel, and anodized aluminum behave differently; counter-face roughness strongly affects transfer-film formation.

Step 5 — Consider lubrication

If even boundary lubrication is available, the gap between CF30 and bearing grade narrows considerably.

Step 6 — Validate near the design boundary

If the application operates near the material's limiting PV, or if temperature and counter-face conditions are unusual, application-specific testing is recommended.

How Should the PV Values Be Interpreted?

The PV 5 and PV 15 test conditions discussed above are accelerated laboratory conditions. A conservative screening approach can be obtained by applying a safety factor to the published limiting-PV values:

These ranges are engineering screening values derived from the published Lpv data — they are not manufacturer-rated continuous PV limits. Actual allowable PV depends on temperature, pressure, sliding velocity, counter-face material, surface roughness, lubrication, duty cycle, component geometry, and the specific PEEK formulation.

Temperature Can Change the Result

Temperature should be considered separately from PV. As interface temperature increases, PEEK mechanical and tribological performance can change significantly. The engineering screening approach used in this analysis applies approximate reductions to allowable PV as temperature increases:

These factors are conservative engineering screening assumptions, not universal material specifications. If the sliding interface approaches very high temperatures, application-specific testing becomes increasingly important. For the underlying temperature limits, see our PEEK temperature range guide >>

The Most Important Engineering Limitation

Wear is a tribosystem property, not a material constant. Friction and wear can change substantially with counter-face material, surface roughness, contact pressure, sliding velocity, temperature, lubrication, alignment, duty cycle, and transfer-film formation. Published wear data should therefore be used for material screening and grade comparison, not treated as a universal design allowable.

The most reliable conclusion from the published comparison is not that one grade always wins. It is this: CF30 is generally favored when stiffness and load-bearing capability are critical, while bearing-grade PEEK is generally favored when low friction and dry-sliding wear performance are the primary requirements.

Can Victrex Data Be Used to Specify PRES PEEK?

No. Published Victrex data should not be treated as specification data for PRES PEEK grades. The Victrex grades discussed in this article — 450CA30, 450FC30 and WG101 — are specific commercial formulations. PRES CF30 and PRES bearing grade are discussed here as formulation categories with comparable reinforcement concepts, not as identical materials.

Published Victrex data can therefore be used to:

• Understand general PEEK tribological mechanisms

• Compare formulation concepts and establish engineering hypotheses

• Guide preliminary material selection

For final material selection, use the grade-specific PRES datasheet and, where necessary, application-specific testing. See the PEEK material selection guide >> for full mechanical, thermal, and physical data on both grades.

Frequently Asked Questions

Data Sources

• Victrex PEEK Properties Guide — Figures 30 and 31 (friction coefficient and specific wear rate, ASTM G137 block-on-ring); pages 15~17 (limiting PV, modified ASTM D3702 thrust-washer). Friction coefficients derived from graphical data are approximate.

• PRES reference data — PEEK material selection guide (tensile, HDT, CLTE, modulus values for CF30 and bearing-grade PEEK, ISO test standards).