Influence of the spring stiffness on friction and wear behaviours of stainless steel/copper-impregnated metallized carbon couple with electrical current

Influence of the support stiffness of the pins on friction and wear behaviours of stainless steel/copper-impregnated metallized carbon with electric current is studied on a pin-on-disc tester. The result indicates that the coefficient of friction increases with an increase of the stiffness at a low velocity or with a small electric current, while at a high velocity or with a large electric current the friction coefficient decreases firstly and then increases as the stiffness increases. The wear rate of pin samples with elastic supports is much smaller than that with rigidity. When the stiffness is equal to 19,000 N/m the wear rate is found to be lowest. In the test, it is observed that there are two different arc discharge phenomena. It is found that the spark discharge is dominant when the pin is connected to power supply anode, while the arc discharge mainly occurs when the pin is connected to power supply cathode. Morphology of the worn surfaces of copper-impregnated metallized carbon is observed with SEM. It is found that the abrasive and adhesive wears are dominant at low velocity or with small electric current, while oxidative wear and arc ablation mainly occurs at high velocity or with large electric current. In comparison with cross-section scar profiles and surface roughness of pin samples in different stiffness, it is found that the wear of pins is severest when it is supported with rigidity and is slightest when it is supported by spring with an appropriate stiffness (19,000 N/m).