The performance and lifetime of gears depend critically on the materials used for quenchning and carburising. Common utilised materials vary depending on the gear's module. Materials like 20CrnTi or 20CrMnMo are usually used for gears with module less than or equal 6. 20CrMnMo or 20CrNi2MoA is recommended for gears with a module between 6 and 12. Materials like 20CrNi2Mo or 17CrNiMo6 are used for gears with a module more than 12.
Two primary considerations should guide material choice for quenching gears and carburising. The material should first have excellent carburising characteristics. Usually offering excellent carburising properties are alloy steels include Cr-Mo steel, Cr-Mn steel, and Cr-Ni steel. Second, the core of the gear has to be guaranteed, particularly for big gears for which materials like Cr-Ni-Mo steel are often used to provide sufficient hardness all around the gear.
Other considerations should also be taken into account in the particular material choosing process including hardness, hardenability, purity, general performance, and cost-effectiveness. Regarding general performance, one should pay close attention to machinability, pitting resistance, toughness, bending strength, fatigue strength, and notch sensitivity. Appropriate material choice may improve gear performance and durability thus guaranteeing long-term stable operation in high-load and high-impact conditions.