Research On Plasma Electrolytic Saturation In Liquid Of Die Steel

Plasma electrolytic saturation(PES) treatment is a kind of simple technology to form a layer in a short time with high hardness and wear resistance. In order to expand its application fields, H13 die steel was treated by PES in KF-[CO (NH2)2] electrolyte in this paper. The influences of treating parameters was investigated on the layer thickness ,distribution of the elements, phase composition, hardness and wear resistance.The growth rate and quality of diffusion layer are related to variable different KF-[CO (NH2)2] electrolytes, and the optimal electrolyte is the solution with 9% KF.The futher results shown that the thickness of the diffusion layer increased with the increasing of treatment time, and arrived at a peak value at 5 min. Also the thickness of the diffusion layer increased with the enhancing of operating voltage, but over long treatment time and over high operating voltage resulted in the degradation of the diffusion layer since high temperature is introduced.The diffusion layer ofH13 die stool steel surface with thickness about 50~90μm could be formed by PES during 3~5 min. The diffusion layer consists of compound layer(3~5μm), diffusion hardened layer (30~50μm) , transition layer (20~40μm) and substrate. Existence of diffusion hardened layer can further improve the hardness and wear resistance of treated layer. The peak value of C, N is presented in the diffusion layer which is similar to that of hardness distribution, the layer composed by Fe2N,Fe3C,Fe3C and [Cr, Fe]2N1-x。For the pre-heat treatment sample, the peak value of hardness of the layer is at the diffusion, about 12OOHV0.1,and the hardness decreased gradually along the diffusion layer, transition layer and substrate, and finally be corned to substrate hardness (45OHV0.1). For the sample without pre -heat treatment, the peak value of hardness is 1050HV0.1, and the hardness gradually decreases as the former sample.The wear rate of the sample after PES is lower about an order of magnitude than the un-treatment sample which indicates that plasma electrolytic saturation can increase the wear resistance of the substrate.