| W-Cu composite materials,which combine excellent mechanical properties of W with thermal and electrical properties of Cu,is widely used as the electrical contact of core components of the high-voltage electric transmission system.At present,there are 24high-voltage power transmission projects in China,with the length of 35000 km,the capacity of more than 350 million k V·A,and the cumulative power transmission of more than 1 trillion k W·h,achieving the role of leadership in the field of high-voltage transmission.The vigorous construction of high-voltage power transmission projects drives the development of related accessories and equipment industries and promotes the upgrade of China’s electrical equipment.There are higher requirements for the electrical contacts carrying various nodes in the power grid,which need to be able to withstand higher voltage,larger capacity and smaller volume,higher reliability and service life.In this paper,the W-Cu composites reinforced with ultra-fine grained tungsten particles and tungsten fibers were prepared by combining mechanical alloying,tungsten sintering and infiltration.Firstly,the preparation process of W-Cu composites reinforced with ultra-fine grained tungsten particles and Cr-coated tungsten fibers was studied,and the growth behavior of tungsten particles at different pre-sintered tungsten skeleton temperatures was explored.Besides,the dynamic analysis of controlling the densification of W-Cu composites was also explored.Secondly,the effect of the content of Cr-coated tungsten fibers on the properties of W-Cu composites reinforced by ultrafine-grained tungsten particles and tungsten fibers were studied.Finally,the effects of different surface-coated tungsten fibers on the properties of W-Cu composites reinforced by ultrafine-grained tungsten particles and tungsten fibers were studied.The microstructure properties,mechanical properties and electrical properties of different W-Cu composites were systematically analyzed and the main results are as follows:(1)Through the research on the temperature of the pre-sintered tungsten skeleton,it is found that the W-Cu composite material prepared by the pre-sintered tungsten skeleton temperature of 1250°C and the holding time of 2 hours is the optimal process.By studying the growth behavior of tungsten particles,the average particle size of tungsten at different pre-sintered tungsten skeleton temperatures was obtained.The tungsten particle growth index and particle growth rate of the W-Cu composite prepared with a pre-sintered tungsten skeleton temperature of 1250°C were determined,along with the main mechanism for controlling tungsten particle growth.(2)Through the study of the arc ablation performance of W-Cu composites,it is found that the increase in the content of tungsten fibers would increase the interception value of arc ablation and reduce the arcing life of W-Cu composites.After synthesizing various W-Cu composite materials reinforced with different layers of Cr-coated tungsten tungsten fibers and the ultra-fine grained tungsten particles,it was found that when 10 layers of 50 μm Cr-coated tungsten fibers were added,the W-Cu composite materials exhibited the highest comprehensive performance.(3)Through the study of the coatings on the surface of the tungsten fibers,it was found that the modification effect of the surface of the tungsten fibers significantly improved the bonding effect of the interface between the tungsten fibers and the matrix.Further research on the surface coating of the tungsten fibers revealed that the W-Cu composites reinforced with Cr-coated tungsten fibers exhibited the highest room temperature tensile properties and high temperature compression properties,and had better deformation ability.Finally,the arc ablation mechanism of W-Cu composites was analyzed.The study found that the arc ablation resistance of W-Cu composites was significantly improved under the combined effect of increased saturation vapor pressure of ultra-fine grained tungsten particles and heterogeneous nucleation of the tungsten fibers. |
