What Types of Lubricants do Bearings Use?
Bearings are components that are crucial to the efficient operations of countless systems, constraining motion while mitigating the friction that occurs between surfaces that move across one another. For rolling element bearings to efficiently operate with long and reliable service-lives, they require ample lubrication. Lubricants ensure that moving parts are separate from one another, making it so that rollers and raceways face little wear and tear over time. To achieve an ideal protective film, a bearing must have the right type of lubrication added.
Generally, a lubricant is a good fit if it can help a rolling element bearing maintain a stable viscosity across a large range of temperatures, help support loads with ample strength, ensure long service lives with stable structures, prevent corrosion between components, and provide a barrier against contaminants and moisture without leaking out of the bearing assembly. If a lubricant is not fit for a particular bearing, it can quickly dissipate, leading to increased frictional heat which can result in damage to the bearing itself, other system components, and assemblies.
Bearing lubricants can come in multiple types, the main categories consisting of oils, grease, and solid films. Oil may be either petroleum based or synthetic, the latter commonly being silicone, diesters, PAOs, and fluorinated compounds. Oil is beneficial for bearings that need quick start up times and less running torque while maintaining high speed abilities. Oil often lasts a shorter time between reapplication as compared to grease due to its evaporation loss characteristics. As such, smaller bearings that are only lubricated once in their lifetime may not be a fitting candidate for oils. Rather, larger bearings that require relubrication during a system’s standard maintenance schedule may benefit from such options.
Grease can be created through adding a thickener to a base oil. These thickeners may be metal soaps, organic materials, or inorganic compounds. Thickeners often have major influence over the overall characteristics of a particular grease lubricant, though the base oil will determine the lubricating properties themselves. Additives are generally implemented for achieving specific performance properties, examples being antioxidant, anti-wear, anticorrosion, fortifiers, fillers, and extreme pressure fortifiers. Generally, greases may be chosen based on their temperature range, viscosity, and stiffness.
Solid films are a type of non-fluid coating that may be applied to surfaces to mitigate friction. Generally, such options are reserved for extreme applications where an oil or grease lubricant cannot properly function or will quickly deplete. These lubricants are a last resort option for environments exhibiting extreme vacuum, temperature, or radiation conditions. Such coatings include graphite, silver, gold, MoS2, and PTFE. Hard coatings may be used as well, those of which come in the form of chrome or TiC lubricants.
It is important to understand that various lubricants may vary in their shelf life, and aging lubricants can provide less performance and protection than newer ones. As such, one should always be adamant about properly storing and procuring lubricants as needed for the protection of their bearings. When it comes time to begin sourcing the various bearing lubricants that you need for your particular operations, NSN Target is here to assist you with competitive pricing and rapid lead-times.
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