1. Introduction: The relevance of rolling bearing technology in 2026
In modern industrial production in the DACH region, the demands on rotating machines are continually increasing. Higher speeds, extreme operating temperatures and the widespread use of frequency converters (VFD) are redefining the load limits of machine components. Rolling bearing technology plays a critical role in this context. In 2026, the use of conventional rolling bearing steel alloys will no longer be sufficient for many high-performance applications. In particular, the high-frequency common mode voltages induced by VFD lead to harmful wave currents that cause electrical discharge erosion (EDM) in standard bearings. These currents penetrate the lubricating film, create microcraters and lead to premature failures due to corrugation (flooding) in accordance with the damage patterns of DIN ISO 15243.
Plant managers are faced with the task of choosing between standard steel, hybrid and all-ceramic bearings. This decision requires a precise analysis of the tribological properties, thermal expansion coefficients and electrical insulation properties of the materials. Incorrect specification leads to unplanned downtime, reduced MTBF (Mean Time Between Failures) and high maintenance costs. This article examines the fundamentals of materials technology, compares current industry standards and provides a well-founded decision matrix for designers and maintenance managers.
2. Historical development of bearing materials
The evolution of rolling bearing materials is characterized by the constant search for higher wear resistance, lower friction and better corrosion resistance. The following table documents the main milestones of this development up to the current state of the art.
| decade | Technological milestone | Industrial impact |
|---|---|---|
| 1900s | Introduction of hardening bearing steel (100Cr6 / AISI 52100). | Standardization of load ratings; Enabling mass production of electric motors. |
| 1970s | First attempts with silicon nitride (Si3N4) for aerospace applications. | Weight reduction and extreme temperature resistance for turbines. |
| 1990s | Market launch of hybrid bearings (steel rings, ceramic balls) for machine tool spindles. | Increasing the limit speeds by up to 40% while simultaneously increasing stiffness. |
| 2010s | Wide use of hybrid bearings in wind turbines and railway technology. | Solution to the problem of bearing damage caused by current passage (electric erosion). |
| 2026 | Standardization of hybrid and all-ceramic bearings in general drive technology. | Integration into IE5 synchronous reluctance motors; Significant extension of the grease service life after DIN 51825. |
3. Functional principles and basic materials technology
The performance of a rolling bearing is determined by the contact mechanics between the rolling element and the raceway. The Hertzian pressure is the central calculation variable here. It describes the maximum stress $p_{max}$ in the contact center, which results from the normal force $F$, the radii of curvature and the elastic moduli of the materials involved.
A comparison of the material properties shows fundamental differences. The standard rolling bearing steel 100Cr6 (DIN EN ISO 683-17) has a density of 7.8 g/cm³ and a modulus of elasticity of approx. 210 GPa. In contrast, silicon nitride (Si3N4), the standard material for ceramic rolling elements, has a density of only 3.2 g/cm³ and an elastic modulus of 310 GPa.
These physical differences have a direct impact on the operating dynamics:
- Centrifugal forces: The 60% lower mass of the ceramic balls drastically reduces the centrifugal forces at high speeds. This reduces the kinematic sliding friction and heat development in the bearing.
- Stiffness: The higher modulus of elasticity of Si3N4 results in less deflection under load. The bearing becomes stiffer, which increases the precision of machine tool spindles, but also reduces the contact area, which slightly increases the Hertzian pressure for the same load.
- Thermal expansion: Si3N4 has a thermal expansion coefficient of 3.2 µm/(m K), while 100Cr6 is 11.5 µm/(m K). This requires a precise calculation of the operating clearance during the design.
The nominal lifespan $L_{10}$ is calculated according to DIN ISO 281. With hybrid bearings, the lower adhesion between ceramic and steel (unequal material pairing) leads to significantly reduced micro-wear. Cold welding, which can occur in steel-steel contacts with insufficient lubrication, is physically impossible.
4. Current state of the art (2026)
Leading manufacturers have adapted their portfolios to the increased demands of Industry 4.0 and electrification. In 2026, specific product lines will dominate the market for high-performance applications.
SKF: Hybrid deep groove ball bearings and INSOCOAT
With the HC5 series (e.g. 6210-2RS1/HC5C3), SKF offers hybrid bearings that are manufactured with C3 internal clearance as standard to compensate for the thermal discrepancy between steel rings and ceramic balls. As an alternative for purely electrical insulation purposes, there are INSOCOAT bearings (e.g. 6210/VL0241), in which the outer or inner ring is plasma-sprayed with a 100 µm thick aluminum oxide layer. These withstand breakdown voltages of up to 3,000 V DC. However, for high frequency currents (VFD), hybrid bearings offer superior protection due to their lower electrical capacity.
Schaeffler (FAG): X-life hybrid bearing
Schaeffler sells hybrid bearings (e.g. HC6210-M-P6-C3) under the X-life label, which are characterized by optimized raceway geometries and special cage designs (e.g. made of PEEK). With grease lubrication, these bearings achieve speeds that are up to 20% higher than those of conventional steel bearings. The PEEK cages ensure high chemical resistance and continuous operating temperatures of up to 150 °C.
NSK: SPACEA series for extreme environments
For applications in corrosive environments, in vacuum or at extreme temperatures (up to 400 °C), NSK offers the SPACEA series. All-ceramic bearings are used here, in which both rings and rolling elements are made of Si3N4 or zirconium oxide (ZrO2). These bearings do not require liquid lubricants and instead use solid lubricant coatings such as PTFE or molybdenum disulfide (MoS2).
5. Selection criteria for system operation (decision matrix)
Specifying the correct bearing type requires systematic consideration of operating parameters. The following matrix serves as a guideline for plant engineers.
| Parameters | Standard steel (100Cr6) | Hybrid (steel rings, Si3N4 balls) | All ceramic (Si3N4 / ZrO2) |
|---|---|---|---|
| Max. Speed characteristic (n dm) | Up to approx. 1,000,000 mm/min | Up to approx. 1,500,000 mm/min | Up to approx. 2,000,000 mm/min |
| Electrical insulation | None (ladder) | Excellent (Insulator) | Excellent (Insulator) |
| Temperature limit (default) | 150 °C (limited by tempering) | 150 °C (limited by steel rings) | > 800 °C (depending on material) |
| Behavior in case of insufficient lubrication | Critical (eating, micropitting) | Tolerant (no cold welding) | Very tolerant (emergency running properties) |
| Corrosion resistance | Low (rust formation possible) | Medium (steel rings vulnerable) | Absolute (chemically inert) |
| Relative acquisition costs | 1x (base) | 3x to 5x | 10x to 50x |
6. Performance metrics and benchmarks in real use
Field tests in the process industry confirm the theoretical advantages of hybrid and ceramic technology. In a case study from the paper industry, the drive motors (250 kW, frequency-controlled) of the dryer section were analyzed. The standard steel bearings failed on average after 12,000 to 15,000 hours of operation due to electrical erosion (corrugation) and subsequent cage fracture.
After converting to hybrid bearings (SKF HC5 series), the MTBF increased to over 45,000 hours. In addition, a reduction in storage temperature of an average of 12 °C was measured. According to the Arrhenius equation, this temperature reduction doubles the theoretical grease service life. Friction losses in the bearing have been reduced by 25%, which leads to a measurable reduction in energy consumption during continuous operation.
In high-speed milling spindles (n = 24,000 rpm), the use of hybrid bearings with PEEK cages showed a reduction in vibration amplitudes by 15%, which directly resulted in improved surface quality of the machined workpieces (Rz values fell from 4.2 µm to 3.5 µm).
7. Integration challenges in brownfield plants
Retrofitting hybrid or all-ceramic bearings in existing systems requires technical expertise. A direct 1:1 exchange without checking the environment design is risky.
The main problem is the different thermal expansion behavior. If a full ceramic bearing is mounted on a steel shaft, the shaft expands more than the ceramic inner ring when heated. This leads to a massive increase in the pressure in the joining seat, which can burst the inner ring (note the tensile stress limit of ceramics). Conversely, the outer ring can become loose in the steel housing as it cools.
With hybrid bearings, this problem is minimized by the steel rings, but the internal clearance must be taken into account. Since the ceramic balls hardly expand when heated, the operating clearance changes differently than with pure steel bearings. As a rule, increased radial clearance (C3 or C4 according to DIN 620-4) is selected to prevent the bearing from warping in the event of temperature gradients between the inner and outer rings.
In addition, the hardness of the ceramic balls requires the utmost cleanliness during assembly. While steel bearings embed small dirt particles into the raceway to a certain extent (rolling over), hard particles in a hybrid bearing act like abrasives. The ceramic balls push the particles into the softer steel rings, resulting in rapid pitting. Compliance with the cleanliness classes according to ISO 4406 for lubrication is essential.
8. Future outlook (2026-2030)
Rolling bearing technology is developing towards mechatronic systems. By 2030, the integration of thin-film sensors directly on the bearing rings will become the standard for critical drives. These sensors measure temperature, strain (load) and high-frequency vibrations (acoustic emission) directly in the load zone.
In the area of materials, research on graded ceramics is being intensified. These materials combine the toughness of steel at the core with the hardness and insulating ability of ceramic on the surface, without the disadvantages of coatings (chipping). In addition, additive manufacturing (3D printing) of ceramic cages enables more complex geometries for optimized lubricant distribution with minimal quantities (MML lubrication).
The trend towards electrification of industrial trucks and automated guided vehicle systems (AGV) is driving the mass production of small hybrid warehouses, which will lead to a further reduction in manufacturing costs. The price difference between high-quality steel bearings and hybrid bearings will continue to narrow in the lower size segment.
9. References and standards
- DIN ISO 281: Rolling bearings - dynamic load ratings and nominal service life.
- DIN 620: Rolling bearings - tolerances (Part 2: Tolerances for radial bearings, Part 4: Radial internal clearance).
- DIN EN 61800-3: Speed-variable electric drives (EMC requirements, relevant for VFD-induced currents).
- VDI 2204: Design of plain and rolling bearings.
- DIN ISO 15243: Rolling bearings - damage and failures - terms, characteristics and causes.
Summary and procurement
The choice between steel, hybrid and all-ceramic bearings is an engineering decision that must take into account parameters such as speeds, electric fields, temperatures and lubrication conditions. While 100Cr6 steel is sufficient for standard applications, hybrid bearings offer the most effective solution against VFD-related electrical erosion and for increasing limit speeds. All-ceramic bearings are reserved for special applications under extreme environmental conditions. The correct specification drastically reduces the total cost of ownership (TCO) and ensures system availability.
UNITEC-D GmbH is a certified and reliable partner for industrial maintenance. For the specification-compliant procurement of these critical components, the UNITEC-D E-Catalog offers a verified selection of standard-compliant rolling bearings from leading manufacturers.
