Study On Boronizing Process And Microstructure Property Of Steel

Boron was added into plain carbon steel by pulse electrodeposition to improve theabrasion resistance and corrosion resistance. This dissertation studied boronizing processand detecting performance by molten salt electrochemistry. The process parameters weredetermined by Theoretically Orthogonal analysis`method in theory. The formula ofmolten salts was studied. The process parameters were systematically studied by glowdischarge spectrometry （GDS）, optical microscope and X ray diffraction （XRD） in fact.We can define the boronizing process the best proportion of molten salt and the optimalprocess parameters at last. Facts prove the theory and real phase consistency.We can test the abrasion resistance and corrosion resistance by the best of moltensalt ratio and optimal technological parameters of boronizing. The result of experimentwas analyzed from the point of view of theory.The possible reaction and phases in the boronized layer were calculated usingthermodynamic theory. Layer growth kinetics curve was analyzed by measuring thethickness as a function of treatment time and temperature and the diffusion rule of boronin substrate during process of electrodeposition was studied.The results showed that the optimal formulation of the salts was NaCl:KCl:NaF:Na₂B₄O₇=1:1:3:0.05（mole ratio）. The optimal parameters of boronizing process werecurrent density of60mA/cm², electrodeposition time of60min, electrodepositiontemperature of850℃, duty cycle of20%and the period of1000s. Wear resistance ofboronizing layer was improved notably. The sequence of Corrosion resistance inboronizing layer is mix acid50%H₂SO₄、20%NaOH、10%HCl、10%FeCl₃in turn.Diffusion coefficient values of boron in the carbon steel at750℃,800℃and850℃were1.17056-10m²/s,2.70111×10^-10m²/s,8.63556×10^-10m²/s, the activation energy was127kJ/mol respectively.