Salt-bath nitriding (Tufftride / Melonite / QPQ) — fast, dirty, effective

What a 90-minute cyanate-bath FNC cycle delivers compared to a 60-hour gas retort, what QPQ's oxide step actually adds, and which dies belong in a salt pot and which do not.

9 min readLesson 4 of 12

A Tier 1 automotive stamper running galvanized panels needs 40,000 carbon-steel die inserts a year nitrided for galling resistance. Gas FNC certificates run 24-hour cycles. Plasma runs 12. A salt-bath house in the same county delivers 90-minute cycles with the same compound layer target on the certificate, 10-15 µm ε-rich. The salt-bath process is the correct metallurgical fit for this volume class, and the reasons it fits are the subject of this lesson.