| The lightning-proof gap materials of transmission lines are usually manufactured by carbon steel, which are destroyed easily when lightning stoke happen in transmission line due to their poor arc erosion resistance.Therefore, the protect effect of insulation chain and transmission line needs to be improved. Tungsten-copper alloy is a potential lightning-proof gap material, which is a pseudo alloy composed of tungsten and copper prepared by powder metallurgy. Tungsten copper alloys have been widely used as electrical materials, electronic packing, heat sink materials and military materials due to its excellent properties in arc erosion resistance, welding resistance, high strength and hardness. This dissertation studied the microstructure, physical and mechanical properties, corrosion resistance and arc erosion properties of W80 Cu Ni0.3 alloy with different Ti B2 addition prepared by pressing and infiltration. The following conclusions can be drawn from this investigation:W80Cu Ni0.3 alloy with 0-2wt% content of Ti B2 were prepared by common mould pressing and infiltration, cold isostatic and infiltration.The effect of Ti B2 contents and tungsten skeleton preparation methods on the microstructure and properties of W80 Cu Ni0.3 alloy was investigated. The research shows that the density, hardness and conductivity of W80 Cu Ni0.3 produced by the two methods were reduced with Ti B2 contents increasing, and the zone of copper was also decreased. Ti B2 particle aggregation can been seen in the alloy. The physical and mechanical properties of W80 Cu Ni0.3 alloy prepared by cold isostatic pressing and infiltration were better than W80 Cu Ni0.3 alloy prepared by common pressing and infiltration.This is related to the pressure of powder evenly distributed during the process of cold isostatic process. The density, strength and inner-connection of tungsten skeleton green-pressing is better, which lead the liquid copper can be well infiltrated in the tungsten skeleton,while common pressing is single-pression, single-pression made the press loss and uneven distributed, thus made the properties of alloy were worse than cold isostatic process.The corrosion behavior of W80 Cu Ni0.3 alloy prepared by cold isostatic pressing and infiltration were also examined in this study,and then compared with 45 steel. The electrochemical corrosion behavior of tungsten copper alloy with different contents of Ti B2 were also investigated.The research showed that the corrosion resistance of W80 Cu Ni0.3 alloy is better than 45 steel.As a result of salty spray testing,corrosion rate of W80 Cu Ni0.3 alloy is obviously lower than 45 steel, while corrosion rate is decreased firstly and increased subsequently, and then decreased. The change of corrosion rate is related to the loose structure of corrosion product film and its cracking, dropping when formed. This corrosion product film is Cu2(OH)3Cl analyzed by EDS and XRD. The corrosion rate of W80 Cu Ni0.3 alloy after 144 h is far lower than 45 steel during the 3.5wt% Na Cl immersion test, the corrosion film is same as salty spray testing. Compared with 45 steel, W80 Cu Ni0.3 alloy shows higher self-corrosion potential and lower self-corrosion current in electrochemical measurement, which suggested that the corrosion rate of W80 Cu Ni0.3 is lower than 45 steel, so the corrosion tendency of W80 Cu Ni0.3 alloy is lower than 45 steel. The corrosion of W80 Cu Ni0.3 alloy in Na Cl solution is electrochemical corrosion, galvanic cells were set up between two phase with different electrode potential.It was considered that the served as anode phase was attacked preferentially, and the cathode phase was protected,so phase-selective corrosion occurred. Compared with W and Cu/Ni bonding phase, Cu/Ni bonding phase was attacked preferentially in W80 Cu Ni0.3 alloy,so the electrode potential of W is higher than Cu/Ni bonding phase. The electrochemical testing of W80 Cu Ni0.3 alloy with different contents of Ti B2 showed that the self-corrosion current of W80 Cu Ni0.3 alloy is increasing with Ti B2 content increasing, which suggest that the corrosion resistance of tungsten copper is worse with the increasing of Ti B2.This paper also studied the electric arc erosion properties of tungsten copper with different content of Ti B2 prepared by cold isostatic pressing and infiltration. The results showed that the vacuum discharge of W80 Cu Ni0.3 alloy is anode arc erosion, which contain gasification evaporate and liquid splash. The anode material eroded more than cathode material. The anode surface formed some pits and Cu/Ni metal balls and exposed W particles and microcracks can be seen in the cathode surface. The ablative resistance of tungsten copper alloy with the contents of Ti B2 increased after 200 times discharged. The arc erosion of W80 Cu Ni0.3 alloy without Ti B2 mainly occurred in Cu/Ni zone, and liquid Cu/Ni splashed seriously, thus resulted in bigger erosion pits, while the arc erosion of tungsten copper alloy with Ti B2 mainly occurred in the phase boundary of Cu/Ti B2, so the liquid Cu/Ni splashed less and the erosion pits were smaller than that of tungsten copper without Ti B2. In addition, some tiny scratches and black ablation traces could be seen on the surface of W80 Cu Ni0.3 alloy without Ti B2 alloy after 25 times simulative lightning impulse. The microstructure of erosion surface shows some erosion pit and bright white zones, which are Cu/Ni according to the above analysis. |
PDF Full Text Request