A hard-case requirement does not define the stock condition
When nitriding is planned to extend the life of a wear-loaded shaft, the discussion often begins with surface hardness. The condition of the supporting core must also be established. Nitriding 135 / 135M is an aluminum-bearing steel family developed to respond to nitride formation. This does not remove the importance of prior heat treatment or core strength. Writing that a raw bar will be nitrided does not say whether annealed stock or material brought to a specified mechanical condition is required. Describe the next manufacturing step together with the supplied starting condition to keep case and core connected.
Nitriding and carburizing have different roles
Nitriding develops a surface layer through nitrogen, while carburizing enriches the surface with carbon and uses a different hardening sequence. An enquiry for a carburizing steel such as 9310 should therefore not be combined with Nitriding 135 under one generic final-treatment heading. Both may target a hard case without being equivalent. Contact loading, case requirements and core condition are assessed with the appropriate material. Avoiding a conventional final quench in nitriding does not mean that distortion or stresses cannot occur anywhere in manufacturing. Effects carried over from earlier operations still matter in the finished part. If a core-hardness record is required, identify whether it is measured at the surface or within a section; do not assess it under the same heading as final nitrided-case hardness.
Machining sequence determines where the layer remains
Rough machining, hole making, smoothing of transitions and approaching final dimensions should be considered with the nitriding plan. If a surface will be ground afterwards, the removal allowance must suit the region that needs to remain at the surface. Not every surface on one component necessarily performs the same function: a bearing seat and a connection thread may have different requirements. The manufacturing document should identify treated and protected areas. Relating stock dimensions to this plan can help avoid unnecessary removal or insufficient allowance leading to a new blank.
Match the 135 and 135M names to the documentation
Commercial correspondence may use Nitralloy 135, Nitriding 135 and 135M together. Do not treat every name as one analysis without checking the UNS and specification defining the modification. Preserve the governing specification and melting route for a product requested as K24065. AMS 6471, for example, includes vacuum-remelting requirements within a bar, forging and mechanical-tubing family. The grade name alone does not demonstrate this production requirement. Connecting number, revision, product form and delivery condition makes quotation acknowledgement and material acceptance clearer.
Separate material-supply scope from processing scope
Supplying bar that will be nitrided and delivering a completed surface-treated component are different tasks. Define the scope at the outset to avoid expecting final case properties from a raw-material certificate. An enquiry to NET can include dimensions, quantity, starting condition, core requirements and subsequent machining information. Final case acceptance belongs to the component’s processing and inspection plan. In a corrosive environment, nitriding should not automatically be assumed to meet every protection need. Lubrication, environment and any additional surface treatment retain separate roles in material and process assessment.
- What core condition is required before nitriding?
- Which surfaces will be machined after treatment, and by how much?
- Does the request cover a raw blank or a fully processed component?