The Study Of Friction And Wear Properties Of CNTs-Ag-G Electrical Contact Composites

In this paper, CNTs-Ag-G composite brushes were fabricated by means of powder metallurgy method. The process included mixing powder, pressing at 200 MPa, sintering for 1h in pure H₂ protective atmosphere at 700℃ and repressing at 400 MPa. The distribution of graphite and CNTs is homogenous in the CNTs -Ag-G composite without obvious micropore and cluster.The effect of the electrical current (0-25A/cm²) on the electrical wear properties of CNTs-Ag-G composite was studied. The results indicate that the temperature of interface rises and the probability of sticking wear becomes more with the increase of the electrical current. Due to the altering of contact manner, the contact resistance decreases and contact voltage drop increases little. With the increase of the electrical current, the sticking wear aggravates, the lubrication film gets damaged, and finally the friction coefficient and the wear mass loss both become bigger. After the comparison of the positive brush and negative brush, it can be found that the wear mass loss of the positive brush is more than the loss of the negative brush because of the physical and chemical reaction on the interface and the existence of the metal transference. The wear mass loss of the positive brush multiplies with the increase of the electrical current, but the loss of negative brush has little relation with the electrical current. The bigger the electrical current is, the more difference between the wear mass loss of the two brushes is.The effect of the circular velocity (5-15m/s) on the electrical wear properties of the composite was studied. The results indicate when the pressure is certain, the contact voltage drop increases a little with the increase of the circular velocity. While the circular velocity reaches a definite value, the contact voltage drop and the wear mass loss increases sharply as the appearance of electric spark. When the pressure is low (1N/cm²), electric spark comes out when the circular velocity reaches 7.5m/s. While the pressure becomes higher (2.5N/cm²), electric spark comes out until 15m/s. Under the condition of constant circular velocity, the contact voltage drop curve falls down after it ascends first, and finally tends to be stable. As the circular velocity increasing, the friction coefficient and the wear mass loss of the mechanical wear decreases, but those of the electrical wear increase. With the increase of the circular velocity, the mechanical relative wear rate increase and the relative electrical wear rate varies as "U" because of co-action of press, electrical current and temperature.