Study On The Design,Preparation And Application Of Mo₂NiB₂ Cermets Coating On The Surface Of Steel

With the development of high technology and modern industry,the properties of components made from traditional processes is gradually unable to meet the demands under hard conditions such as high speed,high temperature,high pressure and strong erosion,etc.In those cases,local damages normally initiated from the surface of material,which ultimately lead to the failure of whole component.Therefore,a proper surface treatment could effectively improve the overall performance of materials.The ternary boride Mo₂NiB₂ has a high melting point and hardness value as well as good chemical stability,thus it has tremendous potential and great application prospect as wear-resistant,corrosion-resistant and heat-resistant material and is considered as an ideal coating material.However,Mo₂NiB₂ ceramet can be quite costly when used as bulk materials.Hence,how to form a layer of Mo2 Ni B2 base ceramet on the surface of material and make this technology have practical meaning are rather important.In this paper,initially,first-principles calculating software VASP was used to simulate the interface diffusion process between steel matrix and Mo₂NiB₂ base ceramet coating based on the model of Mo₂NiB₂ mixed with Fe.Through calculating the binding energy of Mo₂NiB₂,Mo2 Fe B2 and Mo2?Ni,Fe?B2,the feasibility of diffusion of Fe in Mo₂NiB₂ phase was predicted.The results show that Mo2FeB2 phase has the highest binding energy and Mo₂NiB₂ phase has the lowest,while the binding energy of Mo2?Ni,Fe?B2 phase is in the middle,which indicates that it is theoretically feasible that element Fe could substitutional diffuse to the Mo₂NiB₂ phase from the interface between steel matrix and Mo₂NiB₂ base ceramet coating.Next,Vacuum liquid phase sintering technique was used to practically verify the validity of the preparation of Mo₂NiB₂ base ceramet coating on steel?such as Q235steel?.During the experiment,basic materials were consist of pure molybdenum powder,nickel powder,boron powder and chromium powder,etc.The binder,on the other hand,was the composition of absolute ethyl alcohol and epoxy resin.They were together ball-milled to a sizing agent and then brushed on the surface of steel or pressed to an adobe and then conglutinated on the steel.After that,via Vacuum liquid phase sintering technique,a layer of Mo₂NiB₂ base ceramet coating,whose thickness is controllable,was successfully achieved on the surface of steel.Besides,the layer's microstructure and mechanical properties were analyzed in detail,the hard phase isproved as Mo2?Ni,Fe?B2.Therefore,the experimental results turned out perfectly fit the theoretical calculation.Then,an ideal sintering temperature was obtained and the influences of element Cr on Mo₂NiB₂ base ceramet coating were discussed as well.Lastly,in order to meet the demands of different working conditions,the composition and process of Mo₂NiB₂ base ceramet were adjusted and Mo₂NiB₂ base ceramet coatings with different properties were developed through instance analysis.