Bearing Materials

The most common bearing material is 52100 Chrome Steel. This makes up the majority of all standard bearings as it has great mechanical properties for basic machine applications. It has very low chromium content which means it offers minimal corrosion protection. It is a cost-effective solution and is readily available.

52100 Chrome Steel can tolerate temperatures up to 120°C, depending on the cage material. It can run up to 150°C but its hardness values begin to drastically reduce so bearing life is significantly impacted.

One of the most widely used bearing grade stainless steel is 440C. This is a martensitic stainless steel with a very high carbon content. The material has additional chromium content along with the addition of nickel. This makes it much more corrosion resistant to 52100 but is still weak to many chemicals and excess exposure to moisture. It is magnetic as opposed to the 300 series stainless steels.

440C Stainless Steel can operate up to 250°C or 300°C intermittently. At high temperatures, increased bearing internal clearance will be necessary.

This bearing material is used when minor corrosion resistance is required, and the project calls for readily available bearing.

One of the most widely used austenitic stainless steel is 316. This material is relatively soft as it goes for bearing materials but the corrosion resistance properties are incredible. This is often used in off-shore applications due to the impressive salt spray test performance. However, similar corrosion resistance properties can be found in Cronidur30 but without the loss hardness and fatigue life.  316 stainless steel is also considered mostly non-magnetic which can be an additional bonus.  

316 Stainless Steel bearings can be run up to 500°C assuming there is no cage. The material is non-hardenable so it can only allow for semi-precision applications with very low loads and low speeds. 

Silicon nitride has better high temperature capabilities than most metals combining retention of high strength and creep resistance with oxidation resistance. In addition, its low thermal expansion coefficient gives good thermal shock resistance compared with most ceramic materials.

Silicon nitride is the material of choice for many specialist applications like ultra-high vacuum, medical devices, semiconductors among many others. 58% lighter than traditional steel, Silicon Nitride provide a weight saving benefit and due to the reduction in weight there is a reduction in the centripetal force generated by the rolling elements therefore for similar application when compared to bearing steel silicon nitride offer a significantly increased fatigue life time. Unlike other ceramic materials silicon nitride has the ability to carry similar loads to that of bearing steel however, due to the hardness of the material any application with shock loading is unsuitable for use of silicon nitride or any other ceramic materials for races.

Aspects such as lower density gives both a weight saving and an increased life as the centripetal force acting upon the bearing is less therefore reducing the wear on the rolling elements. However, due to the hardness and surface finish limitations, full Silicon Nitride bearings are not suitable for low noise applications and a hybrid version would better equipped.

Speed ratings are reduced when the a fully silicon nitride bearing is used; however, with a hybrid arrangement significantly increases speed capabilities to traditional steel bearing. There are also lower load ratings to a traditional steel bearing.

Silicon nitride bearings have very good corrosion resistance and a large temperature range from -210°C to 800°C without a cage. They are non-magnetic and electrically insulating.

Zirconia (ZrO₂) was developed in the 1960s and ’70s and was used to produce the external tiles which created a thermal barrier on the space shuttle that allowed it to re-enter the earth’s atmosphere therefore, zirconia is the material of choice for high temperature applications. The thermal expansion and density of zirconia is close to steel than that of any other ceramic material so it does not have the same weight saving and thermal shock resistance that are found in other ceramic materials.

Best used under low loads, Zirconia bearings are used in high temperature  -190°C to 850°C without cage, and highly corrosive applications. Like many other ceramics, Zirconia is non-magnetic and electrically insulating.

One huge benefit is Zirconia has a similar Thermal Expansion Coefficient to 52100 Chrome Steel and the same as 440C Stainless Steel. This allows for mechanical systems to expand and contract in sync throughout

temperature gradients.

Zirconia is highly corrosion resistant but may show signs of degradation after continuous exposure to steam or hot water. Please consult our bearing experts to discuss Zirconia’s degradation at low temperatures as well to determine if this is a suitable option for your application.

Less frequently used than other ceramic materials due to its raw materials cost and difficulty to machine, silicon carbide offers the best heat and corrosion resistance of all the ceramic materials.

Silicon Carbide is best used under low loads and in highly corrosive environments. It exhibits the best corrosion resistance out of popularly utilized bearing ceramics. It also allows for one of the highest temperature ratings at up to 1600°C without a cage. Silicon carbide is non-magnetic and electrically conductive.

Alumina is a very popular technical ceramic but not as commonly used for bearings. Like other ceramics, it is an excellent electrical insulator and exhibits high mechanical strength. It is corrosion resistant except for hydrochloric acids, hydrofluoric acids and strong alkaline solutions.  It can be provided between 96%-99.8% all of which impact mechanical performance.

Our technical bearing experts will guide you through the process of choosing the best ceramic bearing for your application. Alumina might just be the best choice for you.

M50 steel also known as ‘Tool steel’ has high hardness and compressive strength at standard and elevated temperatures with good hot harness and excellent rolling fatigue characteristics. It has been a
natural choice for critical aircraft engine bearings being used up to temperatures up to 500°C as its hardness is still around 55 HRC at this temperature. 

These properties combined with its superior fatigue resistance make it ideal for high temperature high load bearing applications where high precision and stability are paramount, typical applications include
gas turbines and semiconductor assemblies.

CRONIDUR® 30 is a martensitic through-hardened steel that has a similar corrosion resistance to 316L stainless steel it offers a significant improvement over 440C stainless steel which is typically used in
standard stainless steel bearings. It is enriched with nitrogen with extraordinary corrosion resistance and exceptional wear resistance.

Other properties that have defined it as material of choice for high speed spindle bearings include high compressive strength, extreme durability, high and low temperature stability.

CRONIDUR® 30 bearings have been proven to provide solutions in applications such as oil exploration down hole equipment, cryogenic pumps and super precision optical equipment. When combined with ceramic balls to form a hybrid bearing life will also be significantly increased.

Provided as AMS 5898, CRONIDUR® 30 bearings have a long history of working on the most challenging aerospace and space applications. This material can be trusted to perform and when coupled with support from bearing experts, your design can vastly benefit.

BG42® is a high temperature martensitic steel that excels at high speeds. It is known to combine the corrosion resistance of 440C Stainless Steel with the high temperature hardness of M50 Tool Steel.

These specific properties make BG42® bearings present in high pressure turbine sections within gas turbines or other flight critical locations experiencing extreme heat like bleed valves. The added molybdenum enhances its resistance to corrosion complemented by the high chromium content while also providing some self-lubricating characteristics.

It is supplied as AMS 5749 and has a long lineage both aerospace and space heritage so it can be trusted for the most challenging bearing environments.

Stellite is a material which consists of complex carbides in an alloy matrix; it offers a combination of extremely resilient properties which can be used for the components of a rolling element bearing. Advantages include resistance to wear, galling and corrosion even at extremely high temperatures of 500°C while retaining its hardness of 45HRC and nonmagnetic properties.

Stellite has been extensively used in aerospace applications such inline jet engine valves, landing gear and actuation equipment. This has driven engineers to turn to this material when other exotic alloys and ceramics have not been suitable in bearing applications such as high temperatures valves, equipment operating within range of Tesla magnets, semiconductor applications and cryogenic pumps Speciality Metal & Alloy Bearings.

Beryllium copper is high strength alloy comparable to steel with nonmagnetic properties which can be heat treated for use in bearings.

The use of this material in bearings offers many advantages in extreme environments, excellent heat dissipation with a thermal conductivity between that of steel and aluminium, the material structure makes it suitable for situations of occasional overload, impact, high temperature, low temperature and marginal lubrication.

The material properties make beryllium copper suitable for use in cryogenic, ultra-high vacuum, magnetically sensitive environments as well as certain corrosive applications.

Due to the diversity of environments where engineers & designers are now expecting bearings to operate bearings can be produced in many speciality materials & metal and alloy combinations to produce specific solutions.

Bearings can be produced from the following materials: Inconel, Titanium, Monel, XD15NW, BG42 VIM-VAR, M48 Powder Metal High Speed Steel.

Additional speciality ball options are: Ruby, glass, PEEK, NYLON, Toloron, titanium, The above list is not exhaustive as new materials are constantly becoming available.