Synthesis of arc-resistant W70Cu30 composite alloy with frameless placing of thin-dispersed tungsten phase

Prototypes of high-current electrical contacts W70Cu30 with a frameless packing of dispersed W particles were obtained using precrystallization low-frequency vibration of the compositions “copper melt–uncompacted powder W.” Samples were tested for arc resistance in air in a laboratory device that simulates the operation of an AC contactor. Analysis of the structure (before and after 10 000 arc discharge times) and functional properties (transitional contact resistance and hardness) of the obtained alloys in comparison with industrial contacts W70D30-MP was carried out. It is shown that the difference in the structures of the initial alloys is in the nature of the distribution and size of inclusions of the tungsten phase. In the industrial alloy, tungsten forms a continuous framework of large monolithic formations oriented parallel to the working surface. Their thickness is in the range of 10–100 μm, and length reaches 500 μm. In the experimental alloy, the tungsten phase is represented by dispersed particles with size of 1–3 μm, separated by copper. After repeated arc discharges, these microparticles do not cure and do not form a continuous frame even in the uppermost working layers of the contacts. In the industrial alloy, under the action of the arc, both the dispersion of the framework into individual large particles of tungsten (up to 60 μm) and their subsequent merger occur simultaneously, which leads to an increase in the relief of the working surface. The values of transitional contact resistance up to 6000 arc discharge times in both alloys have similar extents. After that, there is a tendency to a more intense increase in transition resistance in the industrial alloy. Despite the fact that the hardness of the frameless alloy is lower than that of industrial alloy, its undoubted advantages are in dispersion and dimensional stability of inclusions of the hardening tungsten phase under the action of high temperatures (in the arc plasma).