Rapid Surface Hardening of Stainless Steel by Plasma Electrolytic Carburizing

Plasma electrolytic saturation has become an important method to fabricate the modified layer on steel surface, by which a high hardness and good properties on steel surface can be obtained in several minutes. Especially, plasma electrolytic carburizing (PEC) can combine surface hardening of steel and fast cooling in the same electrolyte without reheating. In the present investigation, PEC behaviors of 17-4PH martensitic precipitation stainless steel were systematically studied with different process parameters. The microstructure of the carburized layer was characterized by optical microscope, scanning electron microscope, x-ray diffractometer and x-ray photoelectron spectrometer. The hardnesses of the carburized layers were tested by Vickers hardness tester and nano indenter. The mechanical properties of the carburized layer were evaluated based on load-displacement curves of nanoindentation tests. The results show that 17-4PH stainless steel can be rapid hardened by plasma electrolytic carburizing with the thickness of 20 mu m in 15 min. Hardness of the stainless steel can be increased from 360 to 634 HV0.1. The reasons for the hardness and mechanical property improvement of 17-4PH stainless steel after plasma electrolytic carburizing were analyzed based on microstructural characterization.