NTN develops technology for high fatigue strength Powder Metallurgy gears
March 28, 2012
NTN Corp of Japan has announced the development of an advanced manufacturing technology to produce sintered steel gears for automotive drivetrain and other applications having a fatigue endurance limit of 300 MPA or higher (maximum stress is said to be 700 MPa).
Examples of the small sintered gears
manufactured by NTN Corp.
The company has achieved these high endurance limits by single press and single sinter processing of the PM steel alloy to a theoretical density of 95% of higher.
The composition of the alloy has not been divulged. Powder compacting of the high precision gears is said to be carried out at relatively low compacting pressure of 6 to 10 ton/cm², and improvements have been made to the sintering process in order to attain the material’s fine microstructure and final density of 95% of theoretical or higher.
When used for gears, the high fatigue strength results in 2 GPa or higher strength (1.5 times that of conventional gears machined from bar stock) at the tooth surface, as well as better durability at the base of the tooth.
The high fatigue strength PM gears are expected to replace conventional gears machined from bar stock currently used in automotive applications.
Left: Fatigue test results; Right: Sintering conditions
NTN will coordinate the further development and application of this new technology at its PM part subsidiary Nippon Kagaku Yakin Ltd, which it acquired in September 2011.
Edited by: Paul Whittaker, Editor ipmd.net, [email protected]
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