| In recent years,researchers at home and abroad have carried out a number of studies on the interface control of ceramic particles reinforced steel matrix surface composites,which focused on the structural design,process control,element addition to optimize the interface.These studies compacted the theoretical basis of composites in interface control.However,the interface control methods were mostly from the point of interface design,and interface was merely optimized.The design interface was different from the actual interface,which led the research of the correlation mechanism between interface control and material performance to achieve difficultly.In order to achieve the interface control and WCP/steel matrix composites were used as the research system,the interface remelting method was proposed to adjust the interfacial phase,shape and width.In this paper,WCP/steel matrix composites were prepared by multi-layer preform+powder metallurgy method+interface remelting.The influence of preparation parameters on the interfacial characteristics of the composites was discussed by various analytical methods.The effects of remelting process parameters(remelting temperature and time)on the interfacial characteristics were studied,which laid a theoretical foundation for revealing the interface remelting mechanism of WCP/steel matrix composites.The results show that:the addition of tungsten powder in the transition layer adjusts the composition and structure of the composite layer and the substrate layer to a great extent,and avoids the abrupt change of the substrate layer and the composite layer in the microstructure and properties.WCP size of 75?150pm and 8?75pm were prone to overlap in the composite layer and can cause cracks in the macro-interface,so it is not appropriate to choose smaller size WCP as reinforced particles.When the preform is pressed,the forming pressure should be adjusted reasonably and the size of pressure should match to the actual size required for the particles to be pressed.In this paper,the preform is compressed by the forming pressure of 16MPa,and the WCP/steel matrix composites with excellent performance can be obtained.The micro-interface width increases with the prolongation of remelting temperature.The interface metallurgical reaction does not occur at 1000?(without remelting operation),and ring transition area of a 3?5pm around the WCP appears when remelting temperature reaches 1240?.When the remelting temperature is 1320?,the micro-interface reaction zone begins to melt.The micro-interface thickness increase with the increase of the remelting temperature,and some sharp corners occur with the increase of interface thickness.The interfacial phase at the sharp corners collapse into the matrix with the increase of remelting temperature,and the interfacial interface is connected together to form a large net in the matrix.This network structure has a significant effect on strengthening the connection between WCP and 45 steel substrates including optimizing the structure and improving the mechanical properties of WCP/steel matrix composites.The micro-interface width increases with the prolongation of remelting time,and the variation range is more uniform without sudden increased phenomenon.When the remelting time increase to 120 min,the micro-structure is more perfect and the interface thickness is moderate.When the remelting time is 140 min,the thickness of the micro-structure increase but the finish is destroyed.A large number of block interface phases collapse in the matrix with interface sharp corners,and adjacent WCP overlap.This will make the support of the 45 steel matrix on the WCP greatly reduce and the failure and uprooting of WCP,which affect the overall performance of WCP/steel matrix composites ultimately.The solid phase transition can occur when WCP is heated above 1260?,and the reaction is 2WCW2C+C.The chemical reaction equation of W2C and Fe and binding energy is as follows:The derivative reaction of W2C and Fe is 4Fe+W2C?Fe4W2C,and exist in Fe3W3C-Fe4W2C compound phase.The mathematic model of the interfacial width and remelting temperature(time)after remelting is obtained by Kingstlinger equation dynamics calculation and the model is amended,as follows:... |
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