Hybrid Bearing Designs

Increased Speed Capabilities

• Silicon nitride is 58% less dense than conventional bearing steel. This minimises the centrifugal forces acting on the raceway as the ceramic balls rotate and in turn increases the speed capabilities by 20-50%.
  • Applications: Motorsport, Machine Tool Spindles, Turbomachinery, and Dental Drills.

Increased Lifetime

• Silicon nitride is approximately twice as hard as standard bearing steel. This leads to the ceramic balls polishing the metallic raceway as it rotates, which creates a smoother running surface to help increase the products lifetime.
  • Applications: any application trying to maximize service life.

Run Lubrication Free

• The interaction between steel and ceramic do not induce micro-welds, meaning that hybrid bearings are able to run without the need for lubrication.
  • Applications: Ultra High Vacuum, Cryogenic, Space/Aerospace, Scientific Instrumentation, and Chemical/Medical.

Extreme Temperature Capabilities

• Thanks to its ability to run without lubrication as well as silicon nitride’s low thermal expansion coefficient, hybrid bearings are capable of performing even in cryogenic temperatures (-273°C).
  • Applications: Cryogenics, Scientific Instrumentation, and Space
• Hybrid bearings with specialist high-temperature alloys such as BG-42 and full complement construction can reach temperatures of up to 900°F (482°C).
  • Applications: Gas Turbines, Jet Propulsion, and Exhaust Butterfly Valves.

Minimized Start-up/Running Torque

• Hybrid bearings can effortlessly initiate and sustain rotation through minimising start-up and running torque thanks to not requiring lubrication, being tougher, and having lower inertia than conventional bearings.
  • Applications: Scientific Instrumentation, Paper Mill, and Piezoelectric Motor.

Corrosion Resistance

• When hybrid bearings are paired with stainless steel or UNASIS XtraChrom-coated races they are substantially more resistant to corrosion. Moreover, the use Cronidur® 30 races enhance significant corrosion resistance without compromising on hardness, as you would see with 316 Stainless Steel alternatives.
  • Applications: Offshore, Ultra High Vacuum, Cryogenic, and Food Processing.

Electrical Insulation

• Ceramic materials hinder the electrical current that can pass through bearings, which enhances their performance for those applications needing electrical insulation.
  • Applications: Electric Motors, and Scientific Instrumentation.

Reduced Static Load Capacity

• As ceramic material possesses brittle characteristics, the static load capacity is reduced by about 30% from the conventional steel equivalent, whilst maintaining the same dynamic load rating.

Limited Availability

• The supply chain of hybrid bearings is limited due to the fact that they are highly specialised bearings. It is vital to have a trustworthy supplier with a large investment in high-quality stock such as UNASIS.

Sensitive to Quality

• Ceramic material is brittle, and can therefore be sensitive to cracks, flaws, and contamination as a result of manufacturing. Manufacturing ceramic balls requires technical expertise and rigorous quality control. It is critical to understand that your hybrid bearings come from a reputable business to prevent the chance of premature failure.

Increased Cost

• Whilst cheaper than ceramic bearings, hybrid bearings remain more expensive than their standard steel equivalents. As a highly competitive supplier, UNASIS doesn’t compromise on quality, availability, or technical expertise when it comes to any of our products.

It is important to note that the tailored bearing design and selection approach of UNASIS engineers can help in minimizing and overcoming these drawbacks.

XtrMD Coating

UNASIS XtrMD coating is Molybdenum Disulphide based and can be applied to a wide variety of components. Molybdenum Disulphide (MoS₂) is a naturally minded inorganic material that has become extremely popular as a dry-film lubricant because of its availability, price, and benefits over comparable dry-film lubricants. The coating acts as a sacrificial lubricant that increases bearing life by minimising the coefficient of friction and increasing speed capability.

XtraTD Coating

Tungsten Disulphide has been extensively used throughout a number of NASA, military, and aerospace applications. Heavier and more stable than Molybdenum Disulphide, its lower friction coefficient and ability to slow corrosion in some materials makes Tungsten Disulphide the preferred coating in extreme environments. The coating itself does not bond to itself and is only 0.5 microns thick, negating build-up on top of providing the ideal solution to issues from excessive wear and seizing to galling and fretting.

XtraChrome Coating

XtraChrome is a nodular, thin, and dense chrome coating that is applied to the bearing component in a process that guarantees precise coating deposition. The process comes with several benefits including superior corrosion resistance, increased surface hardness (78 HRC), enhanced bearing life and a reduction in cost and production lead time. The coating also has energy-saving properties due to the reduced surface friction compared to conventional bearings.

Ultra-High Vacuum

To ensure that ultra-high vacuum applications efficiently draw and sustain a vacuum, the applications require components with minimal outgassing properties. Hybrid configurations make excellent solutions in such applications due to their ability to run without lubrication or with vacuum-compatible dry-film lubricants. The most popular vacuum configurations is 440C stainless steel races, silicon nitride balls, and PEEK or stainless-steel cage. Polyether ether ketone (PEEK), is an organic thermoplastic polymer popular for its stiffness and temperature stability, even in extreme environments. This configuration is commonly used for many deposition stages, mass spectrometers, and multi-stage goniometers as well as many other applications.

Cryogenic

Cryogenic applications demand the most of their bearings, due to their operation in the most extreme environments. Compared to stainless steel, silicon nitride has significantly lower thermal coefficient. This allows the balls to retain their shape and rolling dynamics whilst also running lubrication free. When dealing with thermal expansion and contraction, fits and tolerances are crucial. The majority of cryogenic applications use stainless steel for their bearing housing materials that have similar capabilities for thermal expansion as hybrid bearings. When it comes to applications such as cryogenic pumps, rotatory joint for a liquid nitrogen couplings, and cryogenically cooled tool spindles, the experience and expertise of the UNASIS team is guaranteed to provide confidence and security for customers.

Electric Motors

Hybrid bearings have become increasingly popular in electric motor applications, being of particular benefit to the growing wind energy market. Traditional bearings may be prone to electrical pitting, which can occur when an electrical current is passed through the bearing. This can result in increased wear, noise, and lubrication degradation that may lead to the bearing needing to be replaced.

Such issues caused by electrical pitting that may be found in conventional bearings are not an issue within hybrid bearings. This is because the insulating properties of ceramic materials does not allow the current to pass between the races. When paired with other benefits from higher speed capacity to longer service life, it is safe to say hybrid bearings have revolutionised electrical motors.

There are many advantages for using hybrid bearings across a range of industries. Within extreme environment applications these bearings offer an increased lifetime, the ability to run lubrication free, minimised running torque and start-up, corrosion resistance, and electrical insulation. Although there is a reduction in static-load capacity, limitation of availability, sensitively to quality, and increased costs, the advantages far outweigh the disadvantages. Moreover, their already exception speed rating, service lifetime, hardness, and corrosion resistance can be improved even further with the addition of dry film lubrications such as UNASIS XtrMD, UNASIS XtraTD, and XtraChrome coatings. All these combinations have been rigorously tested and evaluated across a range of industries from ultra-high vacuum and cryogenic to electric motors to ensure their optimal performance is achieved across applications.

If your bearings are not performing to the standard that you expect or desire, hybrid bearings could provide the perfect solution. Please get in contact with UNASIS along with details of your application and our knowledgeable experts will advise the optimum bearing solution for you.