The Influence Of Remelting Process Parameters On The Interface Characteristics And Compressive Properties Of WC_p/steel-based Surface Composites

For a long time,researchers at home and abroad emphasized the interface of metal matrix composites that was the interface of the wettability,interface reaction mechanism and stability.The purpose of interface control was to create a stable interface structure that can regulate transfer loads,stress distribution and prevent crack propagation.The various properties of the interface were optimized mainly through structural design,crafts control,element addition and other measures.For the purpose of controlling the interface of WC_P/steel based surface composites.An interface remelting method was proposed to effectively regulate the interface features such as the structure and width of the interface.In order to control the overall performance of the material.In this paper,the composites were prepared by multilayer gradient structure preforms+powder vacuum sintering+interface remelting.The influence of the remelting process parameters(time and temperature)on the interface characteristics and compressive properties of the material were analyzed by a variety of testing methods.Lay the theoretical foundation for the remelting mechanism and industrial application of composite materials.The following conclusions were obtained by analysis:The method of pre-pressing+cold isostatic pressing can be used to improve the density of composite materials,and it was difficult to cause cracks and air holes in the sintering process,which contributes to the improvement of its mechanical properties.By introducing a transition layer,regulated the composition and organization between the composite layer and the substrate layer.Effectively suppressed sudden changes in stress,strain,and thermal expansion coefficient of the substrate layer and the composite layer.At the same time,the second phase generated in the transition layer made the high bonding strength between the substrate layer,the transition layer and the composite layer.That can improve the overall mechanical properties of the composite.No reacting reaction(1000℃),it was un-reaction between WC_P and 45 steel substrate.It belonged to mechanical bonding,and it had poor compressive strength and interface blocking effect.After the remelting process,at 1200℃,a layer of 3 to5μm ring interface reaction area began to appear around WC_P,that is the microscopic interface.As the temperature increased,WC_P continued to dissolve and diffuse.So the microscopic interface also continued to widen and tighter.When the remelting temperature reached 1300℃~1340℃,The microscopic interface was better in width and shape,and an appropriate amount of second phase were generated in the matrix.Under this temperature zone,the composite is excellent in density,structure,interface strength and so on.Through experiments,under the same load,the microstructure of the WC_P/steel base surface composite material has no crack.It proved that the blocking effect of the composites was strong under this temperature range.Through the compression test,the composite material was found to have a compressive strength of about 450 MPa in this temperature range,compared with other remelting temperatures,the compressive strength of the composites reached the optimal interval.When the remelting temperature was constant,the interface gradually became wider as the remelting time increased,and the continuity was gradually strengthened.When the remelting time is 60~100min,the width of microscopic interface was suitable.The interface reaction between WC_P and 45 steel matrixes was the best,and the interface bonding strength was higher at this time.When the remelting time was120~140min,the microscopic interface was too wide.WC_P dissolution was aggravated,it did’nt have integrity and can not play a reinforcing role.And there were a large number of brittle phases in the matrix,multi-component.In summary,it can easily caused WC_P failure,and ultimately reduced the overall performance of WC_P/steel-based surface composites,greatly reducing their service life.Through experiments,it proved that when the remelting time was 40-60min,under the same load,due to the suitable width and bonding strength of the microscopic interface,the shape and quantity of the second phase in the matrix are appropriate,so the WC_P/steel based surface composite microscopically No cracks appeared in the topography under the effect of stress,indicating that the blocking effect of the composite material was strong at this time.At the same time,the compressive strength tested at this time was up to 410 MPa,which had reached the optimal stage.