Step 2 of 8
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Writing the spec — what goes on the print
An annotated nitriding callout template a competent vendor can hit and an incompetent one will refuse, with the eight elements that turn a wish into a spec.
Step 2 of 8Pre-nitride condition
Residual machining stresses relieve at nitriding temperature, and the relief is not symmetric. Long thin features warp, ground surfaces lift, EDM-recast layers crack. The stress relief has to happen before the nitride cycle, at a temperature above the planned nitride temperature, on the finished part. EDM surfaces deserve a specific callout because the recast layer is brittle and stressed regardless of the bulk stress state. Call it out explicitly; do not assume the vendor will add a relief step.
Parts shall be stress-relieved at 565°C for 2 hours after final machining and prior to nitriding. EDM stress relief required where EDM was used.
Quick check
An H13 die tempered at 595°C is going to a 540°C gas cycle. The print needs a stress-relief callout that survives a sub-temper hardness check. What temperature and time?