Quench polish quench
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Quench polish quench (QPQ) is a specialized type of nitrocarburizing case hardening that increases corrosion resistance. It is sometimes known by the brand name of Tufftride, Tenifer or Melonite.[1] Three steps are involved: nitrocarburize ("quench"), polish, and post-oxidize ("quench").[2]
This process is often used when two or more of the following properties are required in a workpiece:
Common applications of the process are for piston rods of shock absorbers, cylinders and rods for hydraulic systems, pumps, axles, spindles, firearm slides and barrels and valves.[3]