Effect Of Honeycomb Preform Structure On W Diffusion Uniformity And Microstructure,Properties In WC/Fe Composites

In recent years,domestic and foreign scholars have carried out many studies on the wear resistance of WC_P/Fe composites under complex conditions such as high temperature wear,however,due to the significant differences in the thermal and mechanical properties between ceramic reinforced particles,metal matrix,it causes significant thermal stress in the above complex conditions,and greatly affects the service life and safety of related parts.In this paper,the microwave sintering and vacuum expendable casting process(V-EPC)are used,dissolving WC particles in a high-temperature environment to fully diffuse W element,and forming a W alloyed layer to prepare the WC/Fe composites can effectively solve the above problems.While it is not difficult to find that the W element cannot be diffused completely uniformly according to the Fick's law and its diffusion equation,so that the W content at different positions in layer are not exactly the same,so it is necessary to study the W diffusion uniformity in the WC/Fe composites,and providing theoretical basis and data support for future related engineering applications.Using metallurgical microscope(OM),X-ray diffraction(XRD),scanning electron microscope(SEM),energy spectrometer(EDS),microhardness tester,three-body abrasive wear machine to characterize and analyze the metallographic,phase composition,microstructure,element distribution and content,microhardness,wear resistance of layer,matrix,and macrointerface,to explore the formation mechanism of layer.The results show that the matrix is a typical hypoeutectic alloy,and austenite dendrites precipitate during solidification firstly,eutectic transformation occurs to form a mixed eutectic structure of eutectic austenite and secondary carbides when the temperature drops to the eutectic point,M₃C type carbides with reticular morphology are formed in layer.Cr is distributed in the eutectic austenite to form(Fe,Cr)₃C,and W and Ni are dispersedly distributed in the primary austenite dendrite to form Fe₃W₃C and Ni₁₇W_3.Refining the grains does not significantly reduce the impact toughness of layer,the hard phase significantly increases its hardness and also increases its abrasion resistance within a certain range.The honeycomb structure has an important influence on the comprehensive properties of composites due to its continuous shape and high specific strength,but the correlation mechanism between its structural parameters and the uniformity of element diffusion is still poorly studied at home and abroad.In this paper,the honeycomb preforms with different structural parameters(same R/d and different R,same R and different d,same d and different R)are set firstly,and the WC/Fe composites with different structural parameters are prepared by microwave sintering and vacuum expendable casting process.When the same R/d and different R,W diffusion uniformity increases first and then decreases as the R increases,and the wear resistance of layer changes in the same trend;when the same R and different d,W diffusion uniformity gradually decreases as the d increases,but the wear resistance of layer changes in the opposite direction;when the same d and different R,W diffusion uniformity gradually increases as the R increases,but the wear resistance of layer changes in the opposite direction.In addition,the structural parameters and the WC particles with different average sizes are selected when has the highest W diffusion uniformity,characterizing and analyzing the microstructure of layers and the microhardness of undissolved particles and microinterfaces,and the degree of WC particles dissolution increases as the average size of WC particles decrease.Finally,the optimal structural parameters and the average size of WC particles are selected to successfully prepare the composites guide,and the effects of casting methods,microwave sintering on the microstructure and properties have been explored.The finite element analysis software ANSYS and COMSOL are used to simulate the processes such as melt infiltration in the holes,WC particles fracture and dissolution,and melt solidification in the holes,which affects the dissolution of WC particles and the diffusion of W elements to form a W alloyed layer.Based on the two-phase solution model and finite element simulation results,building the W element diffusion equation and inputting it into mathematical analysis software MATLAB for next secondary development to calculate the W content distribution curves in the initial holes of layers under different structural parameters.It is found that the structural parameters affect the W content at the initial hole wall,the melt temperature and solidification time in the initial hole center,and the W diffusion coefficient,which in turn leads to differences in the W distribution curves in the initial holes.The above-mentioned characterization and analysis are also performed on the microstructure and properties of layers under different structural parameters,and combining with the distribution variations of the average grain size,microhardness,wear resistance and the results of finite element simulation,to explore the correlation mechanism between preform structural parameters and W diffusion uniformity.