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

Knowledge check

An automotive Tier 1 needs 40,000 carbon-steel stamping die inserts a year nitrided for a galvanized panel line. Three certificates come back: gas FNC at 24-hour cycles, plasma at 12-hour cycles, and salt-bath QPQ at 2-hour cycles. The compound layer spec is the same on all three: 10-15 µm ε-rich. What is the salt-bath process delivering with the shorter cycle, and what should the buyer verify before signing?