Microstructure And Properties Of AgSnO 2 NiO Electrical Contact Materials

Silver cadmium oxide(AgCdO)electrical contact material is known as"universal contact material".This material is gradually replaced because it contains harmful substances Cd.Among all the silver metal oxide electrical contact materials which can replace AgCdO,AgSnO2 electrical contact material has become a research hotspot because of its excellent resistance to fusion and arc erosion.However,a lot of disadvantages have seriously hindered the application of AgSnO2 electrical contact materials such as large contact resistance,difficult processing and low yield.In this paper,four kinds of AgSnO2NiO composites with different content of NiO were prepared by the method of internal oxidation and high temperature sintering.At the same time,thermodynamics,oxygen partial pressure and diffusion of oxygen in silver matrix are also combined.The conclusions are as follows:The calculation of thermodynamics and oxygen partial pressure,the results show that NiO is more stable than SnO2.In addition,the partial pressure of oxygen in Sn and Ni is lower than the partial pressure of oxygen in the atmosphere,which indicated that high temperature sintering can spontaneously generate NiO.The calculation of diffusion of oxygen in Ag matrix,the radius of the NiO particles formed by the oxidation of Ni in the Ag matrix is about 7.904nm.The microhardness,tensile strength and elongation of the four kinds of materials were analyzed.The results show that the NiO and SnO2 particles are dispersed gradually due to the plastic deformation.But in the process of oxide particle dispersion,cracks and voids appear around NiO particles,and it can reduce the density of AgSnO2NiO.The dispersed SnO2 is distributed in the Ag matrix in the form of the similar fiber tissue which has a certain degree of dispersion strengthening effect.Electrical contact performance,resistance to fusion,contact resistance and material transfer characteristics of the four kinds of materials are analyzed.The results show that the welding force and contact resistance of NiO content of 0.5%1#sample is small and stable when the test voltage is increased from 12V to 25V and the current is 10A.It is concluded that the NiO content of 0.5%1#sample has excellent resistance to fusion welding.And the material transfer and material loss of NiO content of 2%4#sample is the lowest.This shows that adding proper amount of NiO can reduce the transfer and loss of AgSnO2NiO electrical contact materials.The arc erosion morphology of anode and cathode of AgSnO2NiO electrical contact are analyzed.With the increasing of the test voltage,the paste peak structure formed on the surface of the anode and the cathode contacts is more obvious.Under the same test conditions,comparison of four types of cathode erosion morphology,it is found that with the increase of the content of NiO,the arc erosion pits,convex peaks and erosion area decrease.The results show that content of NiO has an important influence on arc erosion resistance.