Gear Technology Magazine

NTN Develops Technology for Powder Metal Gears

March 28, 2012

NTN Corporation has developed a manufacturing technology for sintered alloy, capable of manufacturing alloy with an absolute density ratio of 95 percent or higher, and endurance strength of 300 MPa or higher (maximum stress 700 MPa). This allows drivetrain components such as gears that require precision and durability, which had been manufactured with cutting processes until now, to be replaced with sintered alloy.

The powder-metallurgy process is one manufacturing method that is available to reduce waste of materials and energy consumption while manufacturing mechanical components as a means of addressing recent environmental and energy issues. Yet as this process involves compressing metal powder together, micropores can easily develop inside the components, resulting in a decrease in fatigue characteristics compared to components manufactured using cutting process of solid metals. The use of sintered alloys in drivetrain components that require excellent fatigue characteristics had been limited due to this reason.

NTN has made improvements to the powder material and forming and sintering conditions to manufacture high-density sintered compact with an absolute density of ratio 95 percent or higher, using a relatively low casting pressure of 6 to 10 ton/cm2. The combination with NTN's proprietary heat treatment technology results in an endurance strength of 300 MPa or higher under single press, single sintering process. When used for gears, this high endurance strength results in 2 GPa or higher strength (1.5-times conventional products) at the tooth surface, as well as better durability at the base of the tooth. Different combinations of technologies such as metal powder, forming and heat treatment allow high-precision, high-density sintered alloy to be manufactured with a much easier process, making use of the alloy in drivetrain components and other applications.

NTN will coordinate with group company Nippon Kagaku Yakin Co., Ltd. into the future to accelerate the development of products using sintered alloy, as well as the research and development of stronger, higher precision sintered alloy or composite materials. These developments will be used to improve yield, shorten processing times and reduce energy consumption, and applied to the entire product lifecycle in areas such as materials, manufacturing and functionality to help reduce the impact on the environment.