NTN's New “FA Needle Roller Bearings” for Rocker Arms Provide Four Times the Service Life of Conventional Bearings

NTN Corporation has developed the world's first specialized heat treatment (FA treatment*) to produce ultra-fine austenite grains less than half the size in conventional bearing steels, utilizing the inherent increase in the fatigue strength of steel as the grains become smaller. Using this proprietary FA treatment, NTN developed the “FA Needle Roller Bearings” that have a service life four times that of conventional bearings.

Needle roller bearings with high load capacity are used in automobile engine rocker arms (the mechanism that converts the rotational motion of the cam shaft into linear motion, opening and closing the exhaust and intake valves). As automotive engines produce higher output power and become more compact, the demand for longer service life and smaller bearings is also increasing.

To meet this market need, NTN has applied its FA treatment to its “FA Needle Roller Bearings,” attaining four times the service life of conventional bearings. With this new technology, under the same conditions, it is also possible to reduce both the bearing width and the weight by 75% resulting in lighter, more compact bearings.

FA needle roller bearings

NTN's FA Treatment (Fine Austenite Strengthening Treatment)

• NTN developed the world's first specialized heat treatment (FA treatment) that can produce ultra-fine austenite grains less than half the conventional size (average grain diameter under 5 µm) in bearing steel, making use of steel's inherent increase in fatigue strength as grain size becomes smaller.
• This FA treatment technology applies secondary induction hardening at low temperatures to the bearing's carbo-nitrided structure, increasing the service life of these new bearings to four times that of conventional bearings.
• The rolling fatigue service life of bearings made with FA treated material is greatly improved over standard bearings using conventional bearing steel, even under harsh conditions with contaminated lubricants.
• The FA treatment also improves the fracture strength of bearings by 20% and reduces physical changes in bearing dimensions to only 60% of the value for conventional bearings, providing improved gap adjustment, fit, etc.
• Previously, requirements for longer service life in bearing applications were met by developing materials with more additive elements. However, this approach has proven costly and resulted in difficulties in processing and global procurement for so many different specifications. The main advantage of FA treatment is that it solves all these problems, thus making it possible to deploy globally these high-performance bearings with longer service life using bearing steels that are readily available around the world.

The prior austenite grain boundaries
Conventional bearing	FA needle roller bearing