What two processes are commonly used to harden gear elements?

Carburizing and nitriding are two widely used processes for hardening gear elements, particularly in the manufacturing of high-strength gears. Carburizing involves the introduction of carbon into the surface layer of steel at high temperatures, which allows for greater hardness due to the formation of cementite or carbon-rich regions. This process enhances the surface wear resistance while maintaining toughness in the core of the gear.

Nitriding, on the other hand, introduces nitrogen into the surface of steel, often at lower temperatures compared to carburizing. This process results in the formation of a hard, wear-resistant case due to the creation of nitrides. Both carburizing and nitriding are beneficial for increasing the hardness of gear teeth, improving their durability and performance under stress during operation.

The other processes listed, while important in metalworking, do not specifically address the hardening of gear elements in the same way. Tempering and quenching focus more on heat treatment processes for hardening and then reducing brittleness, whereas annealing is aimed at softening materials and improving machinability. Brazing and riveting are joining methods rather than hardening processes, which makes them unrelated in this specific context.