Effect of the addition of carbonaceous fibers on the tribological behavior of a phenolic resin sliding against cast iron

The tribological behavior of novolac phenolic resin matrix composites reinforced with three kinds of carbonaceous fibers was studied in sliding contact against cast iron. Slow pyrolysis was used to obtain carbonaceous fibers from Colombian plantain fiber bundles (crops residues from Uraba region). After the carbonization process the samples were heated up to either 1200 or 1400 degrees C ensuring that many morphological aspects of the natural fibers were retained. Then, novolac phenolic resin with HMTA as curing agent and the carbonaceous fibers were used to obtain a composite material by compression molding process. Samples with different type and volume fraction of carbonaceous fibers were prepared and tested in sliding contact against cast iron in a pin-on-disc wear testing machine. At the end of the tests, the worn surfaces and the debris were analyzed by SEM. A decrease in both friction coefficient and wear of composites was observed with the increase in fiber volume fraction, which was associated to a beneficial effect of the detachment of carbonaceous material from the worn surface. Under the tested conditions, this material remains at the interface between the composite and the cast iron and helps reduce the shear resistance of the interface. On the other hand, surface fatigue and adhesion wear was identified as the dominant wear mechanism of the phenolic resin matrix. (C) 2011 Elsevier B.V. All rights reserved.