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NTN develops special heat treatment technology “HA-C,” contributing to downsizing and lightening of drive units for automobiles

Achieve the industry's highest level in high load capacity of bearing with special heat treatment technology

NTN Corporation (hereafter, NTN) has developed a new special heat treatment technology “HA-C.” This technology achieves the industry’s highest level in high load capacity of bearing, allowing to replace bearings that are more compact and lighter than the conventional bearings. Additionally, it realizes dimensional stability at high temperature, contaminated lubrication resistance, and wear resistance with a high level, which were difficult to achieve with the conventional heat treatment technology, contributing to downsizing, lightening, and saving energy of drive units for automobiles including e-Axles for electric vehicles (EVs).

Background of development

Toward reducing the environmental impact, EVs and hybrid electric vehicles (HEVs) are required to operate in longer cruising distances. In order to improve electricity and fuel efficiency, drive units such as e-Axles and transmissions become more compact and rotate in higher speed, and lubricating oil with low-viscosity are increasingly used. Therefore, ball bearings that can achieve both high load capacity and low friction are needed. In addition, since heat generation and wear increase during high-speed rotation, the rolling bearings are required to reduce the rate of dimensional change and the amount of wear as well.

About the special heat treatment technology “HA-C”

The special heat treatment technology “HA-C” achieves the industry’s highest level in high load capacity. By applying the technology to common steel materials, the load capacity can be improved without changing bearing designs.

The technology uses a large number of hard and fine precipitates to disperse, resulting in extremely high surface hardness and high load capacity. By applying this technology, rolling bearings can adapt to harsh usage conditions including drive units of automobiles.

Features (compared to standard type bearing)

1. High load capacity Increase static load capacity by 2 times and improve rolling fatigue life under heavy load conditions by 7 times. Improving high load capacity enables to replace rolling bearings with more compact and lighter ones
(Replacement example: approx. 13% downsizing and approx. 45% lightening in outer diameter and width*1)
2. Contaminated lubrication resistance Reduce the swelling amount of the indentation circumference generated when rolling bearings bites into debris to 1/2, and improve rolling fatigue life under contaminated lubrication with debris by 3 times
3. Dimensional stability at high temperature Suppress rate of dimensional change at 150°C to less than 1/2
4. Wear resistance Reduce the amount of wear to less than 1/300*2
  1. Averages calculated for some part of the product numbers listed in Grease Lubrication Type High Speed Deep Groove Ball Bearing for EV/HEV (Cat. No.3040/JE) (
  2. Based on NTN’s test under lubricating conditions where oil film is difficult to form

This technology is applicable to NTN products for e-Axles such as the High Speed Deep Groove Ball Bearings and electrical pitting resistant bearings, and solves technological issues of rolling bearings for automotive drive units. NTN will propose the products adopting this technology globally, and contribute to further downsizing, lightening, and saving energy of drive units for automobiles.

We will exhibit deep groove ball bearings for automotive drive units adopting this technology at “Automotive Engineering Exposition 2024 YOKOHAMA” to be held from May 22 to 24 in Pacifico Yokohama.


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