How to protect against gas nitriding?

The depth of gas nitriding is generally 0.2~0.4mm, so you just need to protect both ends of the pinhole with metal seals to prevent nitrogen from entering. You can avoid the hardening of the pinhole. For example, you can use copper sheets on both sides of the pinhole and C-type clamping head for clamping. Ordinary non-metallic seals will not work. Because of the high temperature during processing.