INFLUENCE OF DIRECT CURRENT FIELD ON POWDERPACK NITROCARBURIZING AND MECHANISM ANALYSIS

Powder-pack nitrocarburizing with direct current field (DCF) was carried out on steel 45 and steel 20CrMnMo.The treated specimen was taken as cathode and paralleled with plate anode. The test results indicate that DCF can enhance nitrocarburizing and modify hardness distribution profile along the case depth.The heating effect of DCF enhanced chemical reactions in the agent and accelerated the diffusions of nitrogen and carbon atoms in the specimen.Treating efficiency is improved compared with the conventional powder-pack nitrocarburizing (CPN) process,which is attributed to DCF increased obviously the concentrations of nitrogen and carbon at and around the cathode,accelerated diffusion of the nitrogen/carbon-containing species toward the cathode,while decreased the absorption of nitrogen/carbon atoms by inner wall of the pack box and the non-working surface of the specimen.In addition,DCF's physical effect of enhancing chemical reaction in the agent increased also the productivity and activity of nitrogen/carbon-containing species.