Large Gears: Heat Treating

HMC engineers and metallurgists are continually looking at new design techniques, material selections, and heat treating methods to provide customers with the latest and best products and service.

We know that case hardened steel products reduce maintenance costs and offer longer life cycles.

If the demands on a component are hostile and failure carries a high price tag, we will suggest improvements in material specifications and processing techniques, which include carburization, induction hardening, flame hardening, and nitriding.

CARBURIZING

Carburizing and Hardening provides the maximum combination for high strength wear components.

When a gear is carburized, carbon atoms are diffused into low carbon steel at high temperatures, resulting in a high carbon layer. During the heat-treat process a beneficial compressive residual stress is developed within the deep hardened case, producing superior resistance to contact and bending stresses, significantly extending product life.

Deep case carburized gears and pinions are the best option for applications where extended gear life is required and heavy loading and abrasive hostile conditions exist.

INDUCTION HARDENING

Induction Hardening is the process of heating the gear tooth surface and quickly quenching thereafter. The deep case depths achieved by carburizing cannot be attained with induction hardening. One tooth at a time is hardened along the active profile and root area thus minimizing distortion.

Induction hardened gears can extend gear life, although not that of carburized, and perform quite excellently in heavy load, abrasive applications, with improved economy.

ION NITRIDING

Nitriding is a surface hardening process, which can be applied to through hardened gears after quenching, tempering, and machining. The gear is subjected to a nitrogenous atmosphere at moderate temperatures, which causes the nitrogen to be absorbed directly into the surface, forming nitrides. This chemical reaction results in a shallow but extremely hard surface.

Nitriding provides excellent resistance to wear, scoring, and softening, in light to moderate service applications. And because quenching is not required distortion is less than that in other heat treating processes. Nitrided gears are a good option for users of non heavy loaded gears not requiring deep case depths.