The influence of hybrid composites structure on their tribological properties
Andrzej Posmyk, Jerzy Myalski
Quarterly No. 1, 2014 pages 18-22
DOI:
keywords: hybrid composite, structure, alumina, glassy carbon, tribological properties, solid lubricant
abstract The paper presents the influence of a hybrid composite structure containing two reinforcing phases i.e. porous, spherical Al2O3 ceramic particles, coated with glassy carbon film which carries out the function of solid lubricant. This composite is manufactured by a new method developed in 2013, which consists of three stages i.e. pre-form manufacturing from porous foam by means of gelcasting, foam saturation with a glassy carbon precursor and its pyrolysis, followed by the infiltration of the pre-form coated with glassy carbon by a liquid alloy. The new method helps to obtain composites with homogenous glassy carbon distribution which improves their tribological properties. The presence of aluminum oxide increases the hardness locally whereas the presence of glassy carbon mitigates the shear strength. Comparative tribological studies of a composite with an AC-AlCu3Mg1 matrix alloy containing 10% Al2O3 and the hybrid composite in which aluminum oxide spheres have been coated with glassy carbon, both sliding against GJL-300 cast iron in air, confirmed the positive influence of carbon on both the friction coefficient and wear. The friction coefficient at a sliding speed of v = 2.5 m/s and unit pressure p = 2 MPa after wearing-in of the sliding surfaces is 0.08÷0.12 for the composites with glassy carbon and 0.25÷0.32 for the composite which contains only ceramic spheres.