scope:

Increased power density in mechanical power transmission components means greater durability - allowing existing designs to achieve greater capacity, or reduced size and mass for light weighting. After decades of work on adjusting gear manufacturing practices, improving surface finishes, and changing designs to improve performance, trends are now turning toward a focus on improved performance with new gear steel compositions and improved cleanness to enhance overall design.

Three new ultra-high-strength, high-toughness carburizable gear steels are introduced. The new steels provide yield strengths ranging from 180-210 KSI, ultimate tensile strengths ranging from 230-250 KSI, and Charpy impact energies ranging from 35 to 50 ft-lbf, allowing these grades to provide longer life, more power and/or lighter weight. The higher fatigue strength of these steels is compared to more commonly used gear steels and an analysis is presented illustrating a potential for either a 30% reduction in gear set mass, or a 45% increase in gear set torque capacity.