Study On Process And Microstructure Property Of RE-boron-vanadizing For Carbon Steel

There are many problems about process,microstructure and properties of bonding espencially boron-vanadizing and systematic experiments data and all-rounded analysis are lacked presently. Boridng,boron-vanadizing and RE-boron-vanadizing experiments which adopt solid powder method based carbon steel have been done in this paper for affording academic guidance to industrialized production and propeling more applications of boriding and boron included multicomponent thermochemical treatment in industry.Orthogonal experimental project is designed. A series of process experiments have been done by altering dispensation of permeation reagent and process parameter.The effects of dispensation of permeation reagent and process parameter on structure and properties of the layers have been studied According to thickness and microhardness of the layers,and then rational dispensation of permeation reagent and process parameter are confirmed for the three processes.Then structure pattern,content and distribution of element permeated,phase makeup,microhardness and brittleness for the layers are tested roundly.The results show:thickness of boriding layer increase with temperature rising ,time prolonging and content of boride provided reagent increasing.Boriding temperature has a maximum effect on boriding layers thickness,and boriding time has a minimal effect on boriding layers thickness.Surface of boron tooth zone is more looser than subsurface;the carbon pick-up and grain coarseness appear in the transition zone;comb tooth of permeation layer of 45 steel is thicker and denser than 20 steel. Boron-vanadizing improves density of permeation layer.All the boriding layers obtain Fe₂B and FeB phase.Content of FeB phase in boriding layer decrease with the increase of sample carbon content.boron-vanadizing is inclined to inhibit FeB phase,and is likely to engender V₂C and VB phase.Microhardness of boron-vanadizing layer is higher than boriding layer,but its hardness gradient is rather big.Microhardness of RE-boron-vanadizing layer decreases for the influence of ihrigizing,and its hardness gradient is less. Brittleness of 20 steel is higher than 45 steel markedly under heavy load,brittleness of RE-boron-vanadizing layer and boron-vanadizing layer is higher than boriding layer, thereforce the boronized samples by multicomponent thermochemical Treatment should be quenched and tempered for the purpose of enhance body intensity.Finally, nucleation and growth model of the layers ,Microscopic diffusion Mechanism of the elements and effects on properties of the layers are discussed on the basis of the results of the experiments.