W-Cu Functionally Graded Materials Prepared By Electrodeposition In Molten Salt (Ⅳ)

W-Cu functionally graded materials (FGM) can be used in many fields because oftheir good erosion resistance, mechanical properties and thermal shock resistance etc.The W-Cu FGMs were prepared by electrodeposition in NaCl-KCl-NaF-WO3moltensalts. The electrochemical behavior and the he electrocrystallization process of tungstenwere investigated in the molten salts system.Three systems were existed in the molten salts, which were NaCl-KCl-Na3WO3F3,KCl-Na3WO3F3, and NaCl-KCl-NaWO3F system. The liquidus temperatures of thesystems were characterized by differential thermal analysis. The lowest liquidustemperature of the systems were612.9℃,597.9℃and609.4℃, individually; and theweight loss rate were3.22%,3.22%and2.05%, simultaneously; The maximum values ofphase transition entropy and the minimum activation energy were close to the eutecticpoint.Cyclic voltammetry, chronopotentiometry, and chronoamperometry were used toinvestigate the electrochemical reaction mechanism and crystallization process of W inNaCl-KCl-NaF-WO3system at700℃. The electrochemical reduction of W6+process intwo-step charge transfer and the cathode process was reversible. Theelectrocrystallization process of silicon is controlled by progressive three-dimensionalmechanism. The diffusion coefficient was calculated to be2.361×104cm/s in themolten salt system at700℃.Ni-W alloy with a certain concentration of good gradient distribution and surfacemorphology can be prepared by electrodeposition in NaCl-KCl-NaF-NiO system on theconditions:100mA·cm-2,800℃,30min. The diffusion coefficient between Ni and Wwas defined by the equation: D=0.01208T-10.57015in the electrodeposition process,which was higher than in annealing process.