After plasma nitriding we want to apply duplex treatment ; what is the appropriate technique and the appropriate coating? thanks.
"QPQ" stands for "Quench-Polish-Quench", which includes a sequence of steps after nitriding: (1) OXIDATION: to form an oxide layer of 2-3 microns by immersing in specially formulated 'salt bath' between 400°C - 425°C; (2) POLISHING: to improve surface finish and (3) RE-OXIDATION in the same salt bath as step (1).
Thanks Mr Yang;
what about duplex treamtment to improve mechanicals properties ( wear resistance and fatigue)?
The process is usually used to improve surface appearance and corrosion resistance. I had done research on this process about 30 years ago and found the corrosion resistance was substantially improved, but I don't know whether this process can improve the wear and fatigue resistance or not.. but the plasma nitriding is supposed to improve wear and fatigue resistance ...
I am afraid my answer will be too obvious, but in general a PVD or a CVD coating may be applied. A concrete choice will depend on the concrete conditions (sliding wear, impact load, temperature, etc.) and application, therefore I may not currently propose a certain coating. Though I feel doubtful, if any PVD or CVD coating may help improve the fatigue limit of a steel. Actually, plasma nitriding should provide that (due to compressive residual stresses in the nitrided layer).
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