| Carburizing is one of the most widely used heat treatment processes in aeroengine,mechanical manufacturing or bearing gear industry.For some parts,during carburizing heat treatment,the parts without carburizing need to be prevented from the infiltration of carbon atoms,otherwise it will affect the subsequent assembly or normal operation of other processes,which needs to be realized by means of anti-carburizing.At present,coating protection technology is widely used.Compared with other methods,this method has the advantages of simple process and low cost.Generally,carburizing temperature is above 920?.At present,the related products are not easy to peel off after sintering at this temperature,which will affect the subsequent processing,slow down the work efficiency and increase the production cost.In order to solve this problem,it is necessary to study a kind of coating which not only has good anti-seepage carbon function but also has good self-peeling property.Based on the research of related literature,the protection mechanism of inert melting film is adopted,and the material selection is based on the surface tension and linear expansion coefficient.The experiment is carried out repeatedly to explore the raw material,optimize the experimental formula,and constantly improve to obtain the best experimental formula.In this paper,the physical and chemical properties of the coating are tested and a nalyzed;the depth of the carburized layer and the change of the metallographic struct ure are examined by metallographic examination;the microstructure is analyzed and di scussed by electron microscope;the film forming temperature of the coating is studied by different thermgravimetry experiment;the phase change of the coating is analyzed by XRD diffraction and the protection mechanism of the coating is advanced Line v alidation.The results show that the optimal formulation of the coating is:glass powder:Bo rax:silica:alumina:dolomite powder=3:3:1.5:1:1.5,the ratio of powder to binder is2:5.The coating has good density,particle size leveling and flow performance,good storage performance,and the coating can form a stable and dense protective film at room temperature It has laid a solid foundation for the later use;during the matrix ca rburizing heat treatment,the coating has no peeling off phenomenon and is compact a nd stable;after the matrix carburizing heat treatment,the surface carbon content does not increase significantly,the coating has the anti-seepage carbon performance,the line ar expansion coefficient of the coating is 6.37×10-6/?,and the gap between the coatin g and the substrate is obvious,and the coating has good self-peeling performance in t he cooling process,and can meet the requirements In addition,the average hardness o f the substrate surface with coating protection is 425HV,while that of the substrate su rface without coating protection is 650HV.Combined with the microstructure of the co ating after sintering,when the thickness of the coating is 0.4mm,the protection effect is the best.It also shows that the coating conforms to the inert melting film protecti on mechanism.When the coating is formed at 647.76?,the compactness is increased,and the sintering is completed at 906.49?,which has a strong anti-seepage carbon e ffect and meets the use requirements of the coating at the carburizing heat treatment t emperature. |
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