Preparation Of Carbon Steel/Stainless Steel Gradient Material By Electrolysis Diffusion (一)

Chromium stainless steel/carbon steel functionally graded materials (FGM) can be used in many fields because of their good corrosion resistance, low cost, high hardness and its gloss. The Chromium stainless steel/carbon steel FGMs were prepared by electrolytic diffusion. The electrochemical behavior and the electrocrystallization process of Chrominum were investigated in the molten salts system. And the corrosion resistance of the gradient materials was studied.By using isothermal saturation method, the solubility and dissolution mechanism of Cr2O3 in NaCl-KCl-NaF molten salt system was determined. The results show that dissolution saturation of Cr2O3 in molten salt takes about 5h at 700℃. The solubility of Cr2O3 increases with the increase of temperature and NaF molar content, its dissolution mechanism is physical dissolve.Electrochemical reduction mechanism of Chrominum in NaCl-KCl-NaF-Cr2O3 was researched by cyclic voltammetry and chronopotentiometry. The results suggest that electrochemical reduction process of Chrominum is quasi-reversible, and it is divided into two steps, namely Cr3++e→Cr2+, Cr2++2e→Cr. Electrocrystallization mechanism of Cr in NaCl-KCl-NaF-Cr2O3 was researched by chronoamperometry. The results suggest that Cr electrocrystallization accords with hemispherical three-dimensional instantaneous nucleation model.In NaCl-KCl-NaF-Cr2O3 molten salt system, with chrome plate as anode and copper plate as cathode, the electrodeposition of Chrominum is carred out. The optimum process conditions for electrodeposition of Chrominum are as follows:XNaCl:XKCl:XNaF=1:1:1-5; deposit temperature are 750℃; deposit time is 90 minutes; current density is 200mA/cm. Chromium stainless steel/carbon steel gradient material with a certain concentration of good gradient distribution and surface morphology can be prepared under these conditions.In CrO33—H2SO4 aqueous solution to stereotype as anode, carbon steel as the cathode for electroplating chromium and deposition of annealing. According to the law of fick diffusion parsing, with the result of the experiment research on the diffusion of Cr in carbon steel, the results showed that:Chromium content for relationship with time and depth is cCr=1/2(1-erfx(Cr)/2(?)) the relationship between Chromium diffusion coefficient and temperature is lnDCr=-4.758×103/T-32.9974, and spreading activation can approximately 39.558KJ/mol; The diffusion in line with the vacancy diffusion mechanism in the Chromium in carbon steel. Polarization curve of sample analysis on the corrosion resistance of Chromium stainless steel/carbon steel graded materials to be higher than that of matrix, and with the increase of Chromium content gradient material corrosion resistance increase in turn.