Comparative Study on Plasma Oxynitriding and Plasma Nitriding for 42CrMo Steel
MIAO Xiaoji1, WU Jiqiang2,3, MEI Wenchen2, SUN Fei1,2, XU Lei3, ZHANG Yulong3, HU Jing1,2
1. Department of Mechanical Engineering, Changzhou Institute of Industry Technology, Changzhou 213164, China;
2. National Demonstration Center for Experimental Materials Science and Engineering Education, Changzhou University, Changzhou 213164, China;
3. Sinopec Oilfield Equipment Corporation, Wuhan 430223, China
In order to enhance the nitriding efficiency, 42CrMo steel was selected as the testing material. Plasma oxynitriding using different air flow in the same pulsed plasma nitriding system for 42CrMo steel was investigated innovatively, and compared with conventional plasma nitriding processing. The cross-sectional microstructures, phases, corrosion resistance were determined by optical microscopy, X-ray diffraction, microhardness tester and electrochemical workstations. The results show that plasma oxynitriding owns much higher efficiency compared with plasma nitriding, thus makes thicker compound layer under the same other conditions. Meanwhile, higher porosity of nitrided layer is obtained. Furthermore, corrosion resistance can be significantly improved due to chemically stable formation and compact Fe3O4 oxide in the compound layer during plasma oxynitriding process, and air flow of 0.3L/min offers the optimum performance for 42CrMo steel due to highest ratio of Fe3O4 to Fe2O3. This research can provide a reference for improving the surface modification process of 42CrMo.
2019, 
