Heat Treatment in Gear Manufacturing

Study Notes

Represents up to 30% of manufacturing costs.
Modifies physical, chemical, and metallurgical properties, optimizing gear performance and lifespan.
Reduces wear and tear while enhancing ductility and strength.

Improves surface and core hardness.
Boosts machinability and minimizes distortions.
Targets specific gear parts, such as teeth or the entire gear, depending on application needs.

Annealing: Involves heating to a high temperature and slow cooling, improving machinability by recrystallizing the material.
Normalizing: Similar to annealing but involves heating above the upper critical temperature and air-cooling, resulting in harder and machinable parts.
Through Hardening: Applicable to medium and high carbon steels; involves heating and cooling while maintaining carbon levels (not suitable for low carbon steels).
Case Hardening (Carburizing): Increases carbon content in the surface layer at high temperatures, creating a hardened surface with a softer core for better ductility.
Nitriding: Utilizes nitrogen gas to create a hard layer of iron nitride on the surface; operates at lower temperatures (500-600°C) than carburizing, preventing quenching cracks or distortion.

Produces a hard outer layer (0.1mm to 1mm thick) with higher hardness compared to carburizing.
Particularly effective for gears made of chrome or molybdenum steel.
Ideal for final processing as it does not cause deformation while enhancing hardness.

Carbonitriding: A variation of case hardening that incorporates both carbon and nitrogen.
Nitrocarburizing: Combines nitriding and carburizing processes to enhance hardness.
Applied Energy Hardening: Includes flame, laser, and induction hardening techniques.

Through hardening: AISI 1045, 4130, 4140, 4145, 4340, and 8640.
Carburizing is better for low carbon content steels where through hardening is ineffective.