Investigation On Microstruction And Proprities Of CuW Alloy Reinforced With Tungsten Fibers

CuW alloys are appropriate candidates in power and nuclear engineering applications such as high-voltage electric contacts,arcing resistant electrodes and deviator plates for fusion reactors,benefiting from the high thermal and-electrical conductivity of Cu combined with the wear resistance and refractory characteristic of W.In this paper,using tungsten fiber(Wf)of higher strength and tungsten particles to form the integral structure of the tungsten skeleton,the tungsten skeleton was filled by the subsequent infiltration process,to obtain a better performance of the CuW alloy.CuW alloys with different layers of Wf were prepared by the sintering-infiltration technique.Also,the effects of different layers of Wf on microstructure and properties were investigated.CuW alloys with surface modificated Wf were prepared by Ni-coated Wf and Cr-coated Wf,the effects of surface modification on the strength and interfacial bonding of Wf and matrix were investigated.CuCrW alloy and CuCrW alloy with Wf were prepared by infiltrating molten CuCr alloy instead of pure Cu into the tungsten skeleton.Properties including high temperature strength,wear resistance and arc erosion resistance of CuCrW alloy and CuCrW alloy with Wf were analyzed systematically.The fine-grained W-Cu mixed powers were prepared by high energy ball milling,and high temperature strength,wear resistance as well as arc erosion resistance of submicron CuW alloys and submicron CuW alloys with Wf were analyzed systematically.The results are as follows:(1)The addition of Wf into CuW alloys resulted in the introduction of two kinds of new interfaces,i.e,the interface between Wf and neighboring tungsten particles,and the one between Wf and Cu.Blind holes appeared at the interface between fibers and the matrix.Hardness and tensile strength reached a maximum value at an adding layer of 10;however,as the Wf layers increased,hardness began to decline,and the porosity and Cu enrichment around Wf exhibited an adverse effect on the overall strength of CuW alloys.(2)The bonding of Wf and matrix was improved by electroless plating Ni or magnetron sputtering Cr on the surface of Wf.There was no hole defect at the interface between Wf and matrix.The good interfacial bonding made the tensile strength of the surface-modified Wf reinforced CuW alloy higher than that of the unmodified Wf reinforced CuW alloy.The electrical breakdown experiment showed that the breakdown point appeared at the surrounding Cu phase,the arc erosion area being larger,and the breakdown pit was shallow,avoiding the arc erosion at the interface between Wf and matrix.(3)CuCrW alloy was prepared by CuCr alloy instead of pure Cu for infiltration of W skeleton,and more sintered neck formed among W particles.Compared with the conventional CuW alloy,the hardness and tensile strength of CuCrW alloy were improved.Wf reinforced CuCrW alloy with well bonded Wf and matrix,higher hardness and tensile strength,higher voltage resistance,better wear resistance and high temperature strength has been obtained.CuCrW alloys reinforced with the Wf before and after the plating of Cr on the surface of Wf exhibited nearly no difference on arc erosion,high temperature strength and friction and wear properties.(4)The submicron CuW alloy exhibited shrinkage phenomenon,and Wf hinders the movement and rearrangement of powder particles during sintering.In comparison to the conventional CuW alloy,the sizes of W skeleton and the infiltrated Cu phase of submicron CuW alloy were reduced remarkably and both the hardness and tensile strength were increased.The fine grain microstructure of submicron CuW alloy exhibited obvious dispersion effect on the arc.The arc erosion area was larger,and the breakdown pit was shallow,showing a higher voltage resistance and a low chopping current.The wear resistance of submicron CuW alloy was mainly abrasive wear,and the friction coefficient was lower.The compression experiments under various temperatures showed that the submicron CuW alloy exhibited a high compressive strength,due to the deformation resistance of Wf.By surface-modification using pre-sputtering of Cr onto the surface of Wf,the high temperature strength of submicron CuW was further enhanced.