Effect of carbonization on mechanical and tribological behavior of a copper-phenolic-based friction material

The effects of carbonization on the mechanical and tribological behavior of a copper/phenolic resin-based semi-metallic friction material were investigated. The results show that a lower carbonization rate leads to a material having higher compressive strength and hardness, as well as fewer cracks. A lower carbonization temperature results in a material with a weak XPS signal of the C-OH bond, while a higher carbonization temperature results in low C-H intensity and increased C-C intensity at the expense of C-H and C=O/C-O groups. The material heat-treated to 400°C has the highest compressive strength and hardness values. Heat-treating to higher temperature causes both values to decline. Both friction coefficient and wear are increased with increasing carbonization temperature. The material carbonized to 600°C exhibits an optimum tribological performance. The worn surface of samples without heat treatment or heat-treated to lower temperatures is covered with a smooth but loosely-bonded layer of wear debris. Only a small amount of counter-face material is transferred to the sample surface. The worn surface of samples treated at higher temperatures is covered with rough sliding tracks. A significant amount of counter-face material is transferred onto the sample surface during the sliding. Carbonized samples demonstrate far better high-temperature heat/oxidation resistance than do non-carbonized samples.