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Bearing Materials — Steels, Stainless, Ceramics, Polymers and Bronze

A bearing's material sets the load rating, the temperature ceiling, whether it rusts and what it costs. Each family below gets the same treatment: a key-facts table, the comparable numbers, and the duty it suits.

11 materialsCompared on 8 propertiesCertificates on request

Short answer. Standard bearings are made of through-hardening chrome steel — 100Cr6, 52100, SUJ2 or GCr15, all the same grade under different national standards. Choose 440C stainless for wet or food contact, 316 where chlorides or chemicals attack, silicon nitride for speed and electrical insulation, PEEK or PTFE for hot wet low-load duty, and bronze where the bearing has to conform to a worn or misaligned shaft.

Key facts — bearing materials at a glance

The eight answers that decide 80% of material questions.

Most common bearing steel	100Cr6 = 52100 = SUJ2 = GCr15 (1.0% C, 1.5% Cr)
Hardness after hardening	59–65 HRC for through-hardened rings and balls
Standard temperature ceiling	120 °C — extended to 200–250 °C by stabilising temper
Corrosion	Chrome and carbon steels rust unprotected; 440C resists; 316 and ceramics do not corrode
Non-magnetic / insulating	Si3N4, ZrO2, PEEK, PTFE, and 316 (low permeability)
Relative cost	52100 = 1.0× · 440C ≈ 3× · ceramics ≈ 8–15×
Material documentation	EN 10204 3.1 mill certificates with heat number on request
Coatings	Zinc, zinc-nickel, black oxide, phosphate, PTFE, DLC — see Coatings & Finishes

Four questions pick the material

Load, speed, temperature, environment — in that order.

Material selection looks like a long list of grades. In practice four questions narrow it to one or two candidates, and the rest of the decision is price and availability.

How much load, and what kind? Through-hardened chrome steel carries the highest radial and shock load per millimetre of section. Polymers carry a fraction of it; ceramics carry high load but need a steel ring around them in most designs.
How fast? Speed is limited by centrifugal load on the rolling elements and by heat. Silicon nitride is 60% lighter than steel, which is why hybrid bearings run at roughly 1.5–2× the dn value.
How hot? Above 120 °C standard chrome steel loses its stabilised dimension and standard grease dies. Above 250 °C only stabilised steel, M50, ceramics or PTFE-bound systems survive.
What is in the air or the fluid? Water, steam, chlorides, acid, food contact, vacuum, or a stray current from a VFD. Each one rules materials out faster than any catalogue column.

Material families at a glance

Pick the column that matches the binding constraint, then open the group.

Constraint	First choice	Fallback	Ruled out
Highest load, dry, clean	100Cr6 / 52100	M50 for heat	Polymers
Washdown, food, weak acids	440C stainless	316 for chlorides	52100 (rusts)
Chlorides, seawater, chemical	316 stainless	ZrO2 ceramic	440C (pits)
Speed and VFD shaft currents	Si3N4 hybrid	Ceramic-coated rings	Steel (electrical pitting)
200–300 °C continuous	Stabilised 52100 or M50	PEEK cage + special grease	Standard grease
Hot wet, low load, chemical	PEEK or PTFE	ZrO2 full ceramic	POM (hydrolyses)
Conform to a worn shaft	Cast bronze	Steel + sleeve	Hardened steel

Browse by family

Bearing steels & bronze

3 materials

100Cr6/52100, M50 high-speed tool steel and cast bronze — the load-carrying backbone.

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Stainless steels

2 materials

440C for wet and food duty, 316 where chlorides and chemicals attack.

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Ceramics

2 materials

Silicon nitride for speed and insulation, zirconia for chemical and magnetic duty.

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Engineering polymers

4 materials

PEEK, POM, PA66 and PTFE — light, quiet, corrosion-free, low load.

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Coatings & surface finishes

8 finishes

When the base material is right but the surface is not: zinc, phosphate, PTFE, DLC.

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Load ratings & life

Reference

How ISO 281 turns material, load and speed into an L10 life figure.

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All 11 materials compared

Indicative values for bearing-grade stock. Exact figures depend on grade, heat treatment and section size.

Material	Density g/cm³	Hardness	Max service temp	Corrosion	Relative cost	Typical duty
100Cr6 / 52100	7.81	59–65 HRC	120 °C (200 stabilised)	None	1.0×	General purpose, highest load
440C stainless	7.70	58–60 HRC	250 °C	Good	2.5–3.5×	Wet, food, medical
316 stainless	8.00	25–30 HRC	300 °C	Excellent	3–4×	Chemical, seawater, low load
M50 tool steel	7.87	60–64 HRC	315 °C	None	6–10×	Aero engine, high dn
Silicon nitride	3.20	≈1500 HV	400 °C (bearing)	Excellent	8–15×	High speed, insulation
Zirconia	6.00	≈1200 HV	400 °C	Excellent	6–10×	Chemical pumps, magnetic
PEEK	1.30	R125	250 °C	Excellent	5–8×	Hot wet, chemical, light load
POM / acetal	1.41	R120	90 °C	Good	1.5×	Light duty, quiet running
PA66 nylon	1.14	R115	100 °C	Fair	1.2×	Light load, damped
PTFE	2.16	R60	260 °C	Excellent	4×	Lowest friction, low load
Cast bronze	8.80	HB 65–90	250 °C	Good (marine)	2×	Bushings, plain bearings

Material shows up in the bearing number

Suffixes are the shorthand for a material change.

Once you know the material, check the suffix before you quote. A 6205 and a 6205-2RS1/S are not interchangeable in a washdown line even though the boundary dimensions are identical. Common markers: /S or S for stainless rings and balls, W64 for a solid-oil or special lubricant fill, HC5 for hybrid ceramic (silicon nitride balls, steel rings), TN9 / TVP for a polyamide cage, M for a machined brass cage. Two bearings can share every dimension and differ in all four of these.

If the number on your drawing has no suffix and the duty is wet, hot or corrosive, the material is probably the open question — not the size. Send the application and we will name the grade and the suffix that goes with it.

What we can document

Material claims are only worth what the paperwork behind them is worth.

EN 10204 3.1 mill certificate with heat number, chemical analysis and mechanical properties.
Dimensional inspection report against the drawing or the ISO 15 boundary dimensions.
Hardness and, on request, case-depth or stabilising-temper records for specials.
RoHS / REACH declarations for coated and plated parts, and food-contact statements for H1 greases.

Frequently asked questions

Which bearing material is best for humid or washdown conditions?

440C stainless for general wet duty, 316 where chlorides or cleaning chemicals are present, and PEEK or PTFE where the load is light and the temperature is high. Standard 52100 chrome steel will rust in a washdown line even under grease, because condensation reaches the ring faces and the cage.

Can I swap a 52100 bearing for 440C without changing dimensions?

Yes for boundary dimensions — ISO 15 sizes are the same. What changes is the load rating (roughly 10–20% lower), the temperature ceiling (higher), the corrosion behaviour (much better) and the price (about three times). Recheck the L10 life if the original selection was close to the limit.

When is a hybrid ceramic bearing worth the price?

Three cases justify it: dn values above roughly 1 million mm/min, electric motors driven by a VFD where shaft currents pit steel races, and applications where a dry or marginal lubricant film must survive. Below those thresholds steel is cheaper and just as good.

Are plastic bearings a drop-in replacement for steel?

Only at low load and low speed. A POM or PA66 bearing typically carries 5–15% of the dynamic load of the steel bearing it replaces, and its stiffness is a fraction of steel's, so deflection and clearance under load change. They are excellent for quiet, corrosion-free, light-duty positions — not for replacing a 6205 in a conveyor head pulley.

What is the temperature limit of a standard chrome steel bearing?

120 °C for a standard bearing with standard grease. Above that the tempering class matters: S1 is stabilised to 200 °C, S2 to 250 °C, S3 to 300 °C, each with a small hardness trade-off. The grease usually fails before the steel does.

Do you supply material certificates?

Yes — EN 10204 3.1 mill certificates with the heat number, on request at quotation stage so they can be costed in. Say so in the RFQ; certificates requested after shipment delay the release.

Applications, by material

Where each grade is actually specified, industry by industry.

Material	Hardness	Temp	Industries	Pages
100Cr6 / 52100	59–65 HRC	120 °C (200 °C stabilised)	Electric Motors · Fans & HVAC · Pumps · Machine Tools · Automotive & EV · Conveyors · Mining & Aggregate · Steel Mills · Wind Energy · Robotics	10
440C	58–60 HRC	250 °C	Electric Motors · Fans & HVAC · Pumps · Automotive & EV · Conveyors · Mining & Aggregate · Robotics	7
316	25–30 HRC	300 °C	Pumps · Conveyors	2
M50	60–65 HRC	315 °C	Electric Motors · Machine Tools · Steel Mills	3
Si3N4	1500 HV	800 °C for the balls, rings limit the bearing	Electric Motors · Machine Tools · Automotive & EV · Wind Energy · Robotics	5
ZrO2	1200 HV	400 °C		0
PEEK	— (polymer, 90 Shore D)	250 °C	Pumps · Automotive & EV · Robotics	3
POM	— (polymer, 80 Shore D)	90 °C	Fans & HVAC	1
PA66	— (polymer, 75 Shore D)	105 °C	Fans & HVAC · Automotive & EV · Conveyors	3
PTFE	— (polymer, 55 Shore D)	260 °C		0
Bronze	60–80 HB	250 °C	Pumps · Machine Tools · Conveyors · Mining & Aggregate · Steel Mills · Wind Energy	6

Not sure which grade the application needs?

Send the duty — load, speed, temperature, fluid — and we will name the material, the suffix and the documentation that goes with it.

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