Carburizing is often considered when a gear needs a deeper hard case and a tough core for demanding contact and bending duty. Nitriding can be a better fit when a shallower diffusion layer and tighter dimensional stability are more important. Neither route is automatically best: material, geometry, load, lubrication, distortion allowance, and the acceptance plan must be reviewed together.
Plan it where the specification calls for effective case depth and a later route can manage heat-treatment distortion. The drawing should define the material, hardness, effective case-depth method, sampling location, and any stock reserved for finishing.
Consider it where lower-temperature diffusion and dimensional stability are central to the project. Suitability still depends on the selected steel, required layer, tooth geometry, and service conditions.
Compare total route cost and risk: blank condition, tooth generation, heat treatment, finishing, and inspection. A hardness number alone does not prove the gear will meet contact, wear, or noise requirements.
For a carburized helical gear that will be ground after hardening, agree the effective case-depth window, hardness test method, datum strategy, finishing allowance, and final profile/lead checks. For a nitrided part, agree the material condition, diffusion-layer requirement, dimensional checks, and any surface treatment limits. PairGears describes heat treatment and finishing as connected stages in its gear manufacturing process guide.
