It is estimated the world will manufacture over 10 billion bearings in 2021, resulting in a market size of over 128 billion USD. 90% of those bearings will outlive the equipment in which they are installed. It is apparent that appropriate bearing lubrication is a critical consideration of mechanical design. This article discusses how Dicronite® dry film lubrication is often an effective solution for the 16.5 million bearings that fail due to lubrication problems.
Bearings reduce friction between two objects during rotational or linear movement. Reducing the friction enhances mechanical performance and efficiencies, allowing components to move at extremely high speeds and carry remarkable loads. Bearings are highly engineered, precision-made mechanisms found in automobiles, heavy equipment, robots, airplanes, computers, spacecraft, machine tools, refrigerators, and ceiling fans. It has been said if something twists, turns or moves, it probably has a bearing in it.
There are different categories and types of bearings distinguished by their purposes and design to carry specific thrust or radial loads. The most common type is a ball bearing. They vary in size and can handle both types of loads. The basic parts of a ball bearing include the:
Shield: Prevents particles from entering the bearing and keeps grease inside
Inner Race: Mounted on the rotating shaft and tends to rotate the shaft.
Outer Race: Mounted to the housing. It is stationary and helps to transfer the loads from the bearing to the housing.
Rolling Element “Balls”: The rolling element ‘balls’ will carry the load distributing it throughout the shafts.
Because these components are likely made of the same metallic material, lubrication is required in order to prevent the parts from galling, seizing, or extensive wear. Greases, oils, and/or solid lubricants are often specified by manufacturers along with the location, amounts and application methods required.
Not only is Dicronite® the global leader in WS2 coating services, it is also the premier dry film lubrication used to coat bearings. While a bearing’s function is to reduce friction within a machine, Dicronite’s function is to reduce friction within the bearing. By applying Dicronite®, engineers improve bearing performance and reduce friction-related wear. The impingement-applied modified tungsten disulfide compound can coat some or all bearing components. It is effective alone, or as a co-lubricant. Engineers often prefer Dicronite® over messy grease and oil because those traditional wet lubricants attract troublesome particles whereas Dicronite® is a dry, clean film that physically bonds with the substrate. Particles do not stick to Dicronite® coated bearings. Furthermore, grease and oil require space within the bearing mechanism, while the Dicronite® coating has a maximum thickness of .5 micron. Tolerances are not compromised with this thin lubricating film.
In order to determine if Dicronite® would extend bearing life, a major bearing manufacturer conducted 3 separate in-house test combinations. They measured and compared temperature and operating time from start to failure between coated and uncoated bearings. The test setup was as follows:
3 different combinations were run, 2 bearings per test setup:
Combination #1: Standard Bearings on Both Sides
Combination #2: Standard Bearing on One Side – Dicronite® Treated Bearing on Other Side
Combination #3: Dicronite® Treated Bearings on Both Sides
- d = 25mm / = 62mm
- B = 17mm
- Cr = 20,600N / C0r = 11,200N
- Clearance = 0,013 ~ 0,028mm
- Material – AISI 52100
- Radial Load = 2,200kgf (total – Hydraulic Cylinder); Radial Load per bearing = 1,100kgf (10,800N)
- No thrust load
- Rotational Speed = 2,000rpm (min-1)
- Clearance = 0,013 ~ 0,028mm
- Lubrication = Oil Bath Mineral Oil Tonna S 68 – Shell (ISO VG 68) – no additives
Dicronite® coated bearings were also tested under extreme pressure conditions and as a co-lubricant with 60W Racing Motor Oil and 90-140W Gear Lube. The tests aimed to determine the effect of Dicronite® on seizure load, weld point, and load-wear index. Test set up was for sliding-on-steel conditions using the Four-Ball Method (ASTM 2783). The following observations were recorded:
The performance of bearings under extreme pressure conditions, as measured by the load-wear index, is significantly improved by the addition of Dicronite® dry lubrication. Dicronite® also provides increased protection in loss of lubrication conditions as shown in the application report regarding military helicopter bearings.
As more and more bearing manufacturers discover the benefits of coating their products with Dicronite®, more and more choose to offer bearings pre-coated with Dicronite®. Such companies include Schatz Bearing Corporation, specializing in aerospace and custom bearings, Boca Bearing Company, concentrating in ceramic bearings, Pacamor Kubar Bearings offering precision and miniature ball bearings, and New Hampshire Ball Bearings, Inc. serving the aerospace, defense, high tech, and medical industries. If you would like to ensure that your project is not subject to one of 2021’s lube-related bearing failures, contact us today! We are happy to provide you with coated samples and assist with validation as needed.