Mechanical Properties of Gear Steels and Other Perspective Light Weight Materials for Gear Applications 2006-01-3578

To improve fuel economy and possibly reduce product cost, light weight and high power density has been a development goal for commercial vehicle axle components. Light weight materials, such as aluminum alloys and polymer materials, as well as polymer matrix composite materials have been applied in various automotive components. However it is still a huge challenge to apply light weight materials in components which are subject to heavy load and thus have high stresses, such as gears for commercial vehicle axles or transmissions. To understand and illustrate this challenge, in this paper we will report and review the current state of art of carburized gear steels properties and performance. The properties and performance data include the following:

• Monotonic tensile data: Young's modulus, stress strain curve, yield strength, ultimate tensile strength, and elongation,
• Strain controlled fatigue data and cyclic stress strain curve,
• Fracture toughness and fatigue crack growth rates data,
• Stress life (S-N) curves in as heat treated and shot peened conditions.

Besides the above purely materials dependent properties, contact fatigue performance of a gear steel will also be reported. Contact fatigue is a surface failure mode which not only depends on materials, but also depends on other tribological factors, such as surface finish and lubricant.

Then the properties and performance data of several perspective light weight materials will be reviewed and compared with those of carburized gear steels. These light weight materials include a powder metal, an aluminum alloy, and a polymer matrix composite material. Finally challenges and potential barriers in applying the light weight materials in power transmission gear applications will be discussed.