Research On The Structure And Properties Of AgCuOSnO₂ Electrical Contact Materials

The universal contact material AgCdO has been gradually replaced due to the high toxicity of cadmium.Among all the contact materials that replace AgCdO,the properties of AgCuO and AgSnO₂ are better.Because of the good wettability and low price between CuO and silver matrix,the arc erosion performance of AgCuO is poor.So,on the premise of ensuring its wettability,researchers add trace elements to AgCuO to change its arc erosion performance.AgSnO2 has attracted wide attention in the industry due to its excellent welding resistance and arc erosion resistance.However,silver-based contact materials with single CuO or SnO₂reinforcement phase are still difficult to meet the demand for high-performance materials.In this paper,AgCuO（10）SnO₂（x,x=2,5,8）electrical contact materials with different SnO₂content were prepared by reaction synthesis method using binary and ternary alloys as raw materials,and their thermodynamic,mechanical and electrical properties were analyzed and tested.The following conclusions were drawn:By calculating the thermodynamics,oxygen partial pressure and diffusion velocity of AgCuOSnO₂ electrical contact material,it is found that Gibbs free energy of both Cu and Sn is less than zero in the process of oxidation,which indicates that both Cu and Sn can spontaneously oxidize to form SnO₂ and CuO in the process of oxidation.By calculating the diffusion rate,it is found that it takes 36 hours for oxygen to diffuse to the core of billet,21hours for copper to diffuse and oxidize,and 25 hours for Sn to diffuse and oxidize,which provides theoretical guidance for the experimental scheme.By analyzing the microstructures of AgCuOSnO₂ electrical contact materials,it is found that due to the different diffusion rates of Cu and Sn in AgSnCu ternary alloys,CuO particles are formed on the surface of AgSnCu alloys and SnO₂ particles are formed on the surface of AgSnCu alloys.The resulting SnO₂ particles destroy the interface bonding state between CuO and Ag matrix and agglomerate the interface bonding area.The interfacial wettability between CuO and Ag is better than that between Ag and SnO₂,which results in the worsening of the processability of AgCuO（10）SnO₂（x,x=2,5,8）prepared by AgSnCu ternary alloy with the increase of SnO₂ content,and the fracture of AgSnO（10）SnO₂（x,x=2,5,8）tends to occur during the processing.The formation of SnO₂ in materials prepared from AgSn and AgCu binary alloys does not destroy the interfacial bonding between Ag and CuO,and its processability is good.The density and hardness of AgCuO（10）SnO₂（x,x=2,5,8）electrical contact materials prepared from binary alloys were tested.It was found that the density and hardness of the samples with 8%SnO₂ content were the highest,and the hardness and density of the samples with 5%SnO₂ content were the lowest.The analysis of resistivity shows that the resistivity increases with the increase of SnO₂ content.By testing the tensile strength and stress-strain curve,it is found that the tensile strength reaches 220 MPa when the SnO₂ content is 5%,and the toughness of AgCuOSnO₂ electrical contact material is the highest.The welding force,contact resistance,material transfer and arc erosion morphology of AgCuO（10）SnO₂（x,x=2,5,8）electrical contact materials prepared from binary alloys were analyzed.It was found that the welding force and contact resistance of AgCuO（10）SnO₂（2）electrical contact materials with 2%SnO₂ content were smaller when the test voltage was 12 V and 18 V.From the arc erosion morphology,it can be seen that the anode of AgCuOSnO₂electrical contact material is pitted,the cathode is convex,and the direction of material transfer is from anode to cathode.With the increase of SnO₂ content,the area of convex peaks and pits formed by arc erosion decreases,which indicates that SnO₂ addition can significantly improve the arc erosion resistance of materials.