Investigation On Preparation And Properties Of Ag-TiB₂-Ni Electrical Contact Materials

With the development of miniaturization,multi-function and high load of electrical components,the increasingly strict requirements are put forward to the silver-based electrical contact materials and it is difficult for single-phase reinforced silver-based electrical contact materials to meet the complex service working environment.Though AgTiB₂ contact material presents excellent resistance to wear,arc erosion and materials transfer,its low mechanical properties,and TiB₂ aggregating in the process of electrical contact,which the reliability of its electrical performance.Based on the above problems,it is proposed to introduce Ni particles into AgTiB₂ electrical contact materials to improve the mechanical and electrical properties of the materials in this thesis.Ag-4wt.%TiB₂-xwt.%Ni（x=0,4,6,8,10）electrical contact materials were prepared by the combination of wet mixing and hot pressing sintering,and the effects of sintering parameters and Ni content on the microstructure,mechanical and electrical properties of Ag-4wt.%TiB₂ electrical contact materials were investigated.The properties and electrical performance of TiB₂-8wt.%Ni electrical contact and commercial contact electrical under different processing conditions were characterized by electrical contact experiments.The research can provide reference and technical support for the design and manu facture of environment-friendly Ag based contact materials with high performance and long life.The effect of sintering parameters on the properties of Ag-4wt.%TiB₂-4wt.%Ni electrical contact materials was firstly investigated,and the results show that the densities of 97.9%,hardness of 96.3 HV and electrical conductivity of 76.2%IACS can be achieved at the sintering temperature of 900℃ and loading pressure of 35 MPa and a holding time of 60 min.At 6wt.%Ni,the tensile strength is 257.04 MPa and the fracture mode is ductile fracture.The effect of Ni content on the electrical properties of Ag-4wt.%TiB₂ electrical contact material was investigated,and the results show that Ni particles can significantly reduce TiB₂ aggregation and the arc erosion.For the Ag-4wt.%TiB₂ electrical contact material without Ni addition,there are high arc energy and long arc duration for make arc and break arc.With increase of Ni content,the average arc energy and arc duration decrease and then increase.The Ag4wt.%TiB₂-8wt.%Ni electric contact material posseses strong resistance to arc erosion,better arc stability,and least arc erosionTo further improve the performance of Ag-4wt.%TiB₂-8wt.%Ni electrical contact materials,the materials were deformed by cold rolling and hot extrusion,and the properties were investigated.It is found that after plastic deformation,the densities of the materials are slightly increased and the reinforcing phases are more uniformly distributed in the silver matrix.The tensile strength of the extruded electrical contact material is 242.34 MPa,which is enhanced by 4.3%,while the elongation is 12.80%,and is increased by 55.71%,demonstrating the excellent plasticity of the extruded material.Finally,the arc erosion performance of commercial contact Ag-12wt.%SnO₂,Ag-8wt.%Ni and Ag-4wt.%TiB₂-8wt.%Ni electrical contact materials in the sintered,extruded and rolled states were systematically compared.The results show that the asrolled material has poor stability and low resistance to arc erosion;Although commercial contacts have good arc stability and arc erosion resistance,However,Ag-4wt.%TiB₂-8wt.%Ni material prepared by extrusion processing within the test range has the lowest arc energy and arc duration compared with commercial contacts,and its arc stability and arc erosion resistance are much better.