The Research And Characterization Of Electric Field Assisted Boronizing

The boriding steel holds many superior properties,such as high temperature hardness,wear resisting and corrosion resistance.So the boriding process lead to wide application in surface peening field.However,traditional boriding layer fabricated by powder boronizing method would mix with the defects such as brittle FeB phase,surface holes caused by high boriding temperature.These disadvantages greatly restrict the further application of boriding process.In the paper,the first step is about improving the traditional boriding process.The filler agent of traditional electric field boriding is SiC.But high electrical conductivity can trigger the high current heat effect.So the experiment will use?-Al₂O₃ instead of SiC to cut down heat effect.The study mainly includes phase analysis,defect and property optimization.The results show that?-Al₂O₃ can obviously improve high temperature resistance of boriding agent and reduce the joule heat effect in electric field.The boriding method can obviously increase boride layer thickness and reduce hole.Eventually,only Fe₂B phase can be detected on sample surface.The results show as follow:In the process of low temperature electric field boriding,boriding agent current will firstly sharp fall,then gradually stabilize at undercurrent density.The temperature in boriding device has the similar change rule.The temperature result also indicate good boriding effect of?-Al₂O₃.In the beginning of electric field assisted boriding,FeB phase and Fe₂B phase simultaneously form on sample surface.Boron potential gradually decline with the passage of boriding time.FeB phase will be consumed and transform to Fe₂B phase.In the end,only Fe₂B phase can be detected on sample surface.The shortest holding time is 2h to make sure to obtain monophase Fe₂B layer.The furnace temperature has direct influence to electric field assisted boriding process.High temperature accompanied by low resistance indicate that the electric field must be enough low to avoid high heat effect.The results at 900?show the best parameter is75V-100Hz.On the contrary,the boriding agent resistance at low temperature is enough high.So high voltage can make sure low electric current and accelerate boriding process.At 780?,boriding voltage can reach to 200V.The boriding layer thickness with the condations of780?,4h is 82?m.And it contains only Fe₂B phase.Furthermore,the highest microhardness value is on the surface,and hardness gradient gently decline to the matrix.