Investigation On Preparation Of Directional Microstructure Of Multi Phase Multi Phase Composite Coating And Its Properties

With the continuous development of science and technology,the surface protection of materials is playing an increasingly important role in engineering.The coating with high wear resistance and corrosion resistance has become an important issue in the field of surface engineering.The oriented crystal can improve the longitudinal mechanical and physical properties of the material,so,it can effectively improve the application performance of the coating.In this paper,the prefabricated coating using SAPS were applied to prepare dense directional structural coatings through high frequency induction remelting technology and controlled cooling technology.The effects of preparation parameters on microstructure and properties of directional structure coatings were studied,and the influence of high alumina bronze content on the wear resistance of composite directional structure was investigated by changing the high aluminum bronze content.The Ni60/aluminum bronze composite coatings was prefabricated by supersonic plasma spraying and then was remelted by means of high frequency induction technology to the coating with different content of high aluminum bronze,with that,the forced cooling was used to controll the coating solidification during the cooling process.The microstructural growth behavior of the composite coating with high aluminum bronze of 20% was investigated with different cooling intensity,and the effect of cooling intensity on the microstructures,element distribution,phase transition and the characteristic of interface growth was studied by OM,SEM(EDS),XRD,EPMA,Origin 7.5?Jade 6.5 software.The results showed that the mechanism of the junction between the substrate and the coating is transferred from mechanical bonding to metallurgical bonding after inducting remolten and controlled cooling.With increment of the cooling intensity,the microstructures of the coating was tansferred from plane to dendrite,cellular dendrite,fine cellular dendrite,and then to dendrite again.The character of the cellular structure is clear and the dendrite grow along the heat flow direction when the cooling water is 80L/h.The microstructrues of the plane crystal,dendrite and cellular dendrite are mainly composed of the compounds and the solid solution with Ni,Fe,Cu,and surrounded with the hard strengthening phases of Cr,C,B elements,and the interface has the characteristics of regular eutectic growth,but the interface of the coating without forced cooling is a divorced eutectic growth.It has the preferred orientation at(111)and(200)crystallographic planes when the speed of cooling water is 80L/h.Then,the coating with different content of high aluminum bronze is treated by forced cooling incondition of cooling water 80L/h,the results showed that with the increase of the content of high aluminum bronze coating,the microstructure is significantly refined,and the organizational change to dendrite cells,and inhibited the diffusion of Fe element to the coating.Finally,The performance of three kinds of coatings was analysised prepared with different parameters and different content of aluminum bronze using microhardness tester and universal friction and wear tester.The results showed that section microhardness of spraying coating is increased at first and then is decreased along the direction of the substrate to coating,but section microhardness of induction remelting and directional solidification coating slightly increased.Under room temperature and dry sliding condition,the wear volume and rate of directional solidification coating are the lowest with the increase of load,which showed the wear resistance of directional solidification coating is the best in the process of the coatings against GCr15 stainless steel.With the increase of the content of high aluminum bronze,the wear volume of the forced cooling coating is decreases firstly and then is increased.When the content of high aluminum bronze is 20%,the wear volume of the coating under the three loads reaches the minimum.In addition,the main wear mechanism of prefabricate coating attributed to the lamellar exfoliation,induction remelting coating attributed to adhesive daub,directional solidification coating attributed to adhesive daub.With the increase of the content of high aluminum bronze,the wear mechanism of directional solidification coating attributed to fatigue palling and adhesive abrasion,slight exfoliation and adhesive abrasion,slight wear,adhesive daub,slight spalling and adhesive daub.