Influence Of Composite Plating And Alloying On The Microstructure And Properties Of Copper Based Contact Materials

The copper based electric contact materials has been studied for more than ten years inour laboratory, which mainly studied on the antioxidant performance of the copper baseelectrical contact materials, and many achievements were obtained. In this paper, the arcresistance and oxidation resistance of copper based electric contact materials were studiedbased on the original research of the laboratory. Including the following aspects: the effects ofyttrium oxide or carbide tungsten on the properties of copper based electric contact materials,especially on the materials the influence of the arc ablation resistance; The antioxidantproperties and sintering performance of silver plating copper powders produced by magnetronsputtering were studied; The effects of adding yttrium on the property of copper, especially onthe oxidation resistance. The resistivity method is applied to the determination of powdermetallurgy sintering process parametersThe results show that:(1) The density and hardness of the materials are improved by adding the right amount ofY2O3. While the content of Y2O3is1.5wt.%, the density of sample reaches a maximum.While the content of Y2O3is2wt.%, the hardness of sample reaches a maximum. AddingY2O3would have an advantage on preventing the copper matrix grain from growing up,which wound contribute to additive being more evenly distributed in the matrix.20000timesarc erosion test shows that: the arc erosion resistance of electrical contact materials addedY2O3is much better than that of the silver plated copper and nickel alloy contact materials,and the new contact still remain a stable and low contact resistance after the test. However,the addition of Y2O3has an adverse effect on the electrical conductivity of copper basedcontact materials.(2) Resistivity method is studied in the sintering process parameters of PM. Bymeasureing in real time the resistivity change of samples during the sintering process, thesintering process parameters of powder metallurgy products can quickly determined. Themethod for the determination of the sintering parameters of PM products has extensiveapplicability. (3) The arc resistance of materials was improved by adding moderate tungsten carbideinto the copper based electric contact materials, but tungsten carbide has an adverse effect onthe density and conductivity of the copper based electric contact materials. Adding a smallamount of tungsten carbide can improve the hardness of the materials, but when the content ismore than6wt.%, the hardness of materials began to decline.The tungsten carbide particleswere plated with copper by magnetron sputtering, we found that the interface of WC/Cucomposite were improve significantly, and the density, hardness of composite materials withcoating tungsten carbide were improved obviously, and the conductive performance of thematerials is also improved.(4) In order to improve the oxidation resistance of copper based electric contact material,we coated copper powder with a layer of silver by the method of magnetron sputtering. Inview of the oxide of the copper powder with different sputtering time under425℃, we finallydetermine that the sputtering time is23min. Through press the copper powder and copperpowder plated silver into compact, and compare the performances of the samples withdifferent sintering time, we found that: the density and hardness of the sample prepared bysilver-coated copper powder at different sintering time are higher than that of the sampleprepared by copper powder; the oxidation resistance of the samples prepared by silver-coatedcopper powder is better than that of the pure copper powder samples, but the conductivities ofthe samples prepared by silver-coated copper powder are poorer than that of the pure coppersamples.(5) When metal copper was added a small amount of rare-earth yttrium (less than0.5wt.%), the conductivity of copper was enhanced, but too much rare-earth yttrium woundexacerbate the conductivity of copper. Based on the oxidation experiments of the yttriumcopper alloy with different the contents of yttrium, we found that: the oxidation increaseweight of copper yttrium alloy gradually reduces with the increase of rare-earth yttrium.When the adding amount of rare earth yttrium were0.1wt.%,0.2wt.%and0.5wt.%, thereduction of sample oxidation weight is obvious; With the addition of rare-earth yttriumfurther increasing, the reduction of sample oxidation weight slow down.Because of thepurification effect of yttrium, the copper with impurity atoms was refined, so a small amountof yttrium (0.1wt.%) was added into the alloy, the hardness of metal copper fell slightly. With the amount of yttrium furtherer increase, the hardness of yttrium copper alloy graduallyincreased.