Forming of complex coatings on the steels by plasma nitriding

In this study, various coatings were applied for AISI 8620 and AISI 52100 steelswith dimension of (20 x 6 mm). TRD carbide coatings were performed by packmethod in the powder mixture consisting of 35 wt.% ferro-chromium powder, 10wt.% ammonia chloride activator and 55 wt.% filler (alumina powder) in a doublestainless steel box at temperatures of 800 and 1000 (C for 5 h in an electricalresistance furnace. Secondly, chromized and non- chromized AISI 52100 steelsion nitrided at gas mixtures of 50% H2 and 50% N2 at temperature of 500ºC for2h. Samples were cleaned in alcohol and placed in plasma nitriding chamber.Plasma treatment was performed in a dc plasma system. The system wasevacuated to 0,025 mbar. The glow discharge was operated with a potentialdifference of 500-600 V. The nitriding temperature was measured usingthermocouple, placed at the bottom of the nitrided sample. After nitriding, thesamples were cut in cross-section and prepared using Standard metallographictechniques. X-ray diffraction analysis showed phases of Cr3C2 and Cr7C for TRDtreatment, phases of Fe2N ve Fe3N for plasma nitriding and phases of CrN, Cr2Nfor dublex treatment on the steels. The wear rate and friction coefficient of hardlayers were depend on the temperature. Both the wear rate and friction coefficientincreased with increase in temperature.2006, 79 pages.Key Words : Chromizing, plasma nitriding, high temperature wear, Friction,Wear