Process Optimization And Erosion Wear Behavior Of WC-12Co Coatings Prepared By APS

In this paper,WC-12Co composite coating was prepared on Q235 steel by atmospheric plasma spraying?APS?method.The microhardness,thichness and bonding strength of WC-12Co coatings were evaluated comprehensively.The Box-Behnken experiment was designed via three factors,including spraying current,argon volume flow and spray distance.The two parameters of response surface and multi-objective parameters optimization based on AHP were applied to optimize the process parameters,and the WC-12Co composite coating was prepared under the selected parameters.The microstructure and properties of the coating under different process parameters were discussed.Scanning electron microscopy?SEM?,X ray diffraction?XRD?and energy dispersive spectroscopy?EDS?were used to study the morphology,microstructure and evolution of the coating.The reason for the formation of the new phase of the WC-12Co composite coating was discussed.The influence of erosion angle on the erosive wear properties of coatings and the wear resistance of coatings under different spraying distance were analyzed from microscopic perspective.The influence of abrasive diameter and abrasive speed on erosion wear performance was also discussed.Results showed that the interaction term between the spray distance and the argon flow rate has great influence on the microhardness of the coating by response surface methodology.Meanwhile,the complex correlation coefficient R²of the two regression model for microhardness is 0.9799.The response surface of coating about bonding strength showed that,the P values of current I and spraying distance d are all less than0.05,and the P values of each interaction item are all greater than 0.05,indicating that the current and spray distance have great influence on the bonding strength of coating.The correlation coefficient of the regression model of the thickness of the coating is0.9876,and the precision of noise ratio is 19.975.The P values of argon flow Q_Arr and spraying distance d are 0.0131 and 0.0002,respectively,which are less than 0.05,and have a great influence on the thickness of the coating.In the process of multi-objective parameter optimization,the importance of evaluation index is obtained through hierarchical analysis.The importance is as follows:microhardness,bonding strength and coating thickness.The maximum grey correlation?Ri?of the eighth groups was 0.98,and the main gas flow rate 2500L/h,current 350A and spray distance 130mm were determined as the optimal process parameters.The regression analysis obtained the optimal parameters of the main gas flow 2500 L/h,current 349.08A and spray distance 129.18mm.Compared with the two different methods,the process parameters are very close,which shows the feasibility of the optimization of the two multi-objective process parameters.The coating with different spraying distance was analyzed by means of SEM,XRD and EDS.The main constituent phase of plasma sprayed WC-12Co coating is WC phase and W₂C phase,as well as a small amount of Co₆W₆C phase.When the spray distance was 120mm,the decarburization behavior is the most serious,and the wear resistance of the coating is poor.When the spray distance is 130mm and 140mm,the decarburization degree is the lightest.The overall structure of the coating is better and the toughness is better.By comparing the different erosion angle of microstructures and morphologies of coatings,the wear loss firstly increase then decrease with the growth of the erosion angle,and amounted to the maximum value when the erosion angle was 60°.The coatings mainly subjected to plastic wear at the small angle?30°?while it subjected to brittle one at the large angle?90°?.when the erosion angle was 30°,micro-cutting and furrow micro deformation and fatigue spalling are characteristic of erosion,with plastic coating anti erosion ability is good;when the erosion angle was 90°,fatigue spalling is the main characteristic,the coating has better anti erosion properties of brittle.