Hybrid composites with ceramic reinforcing phase modified by solid lubricants destined for vehicle subassemblies
Andrzej Posmyk, Jerzy Myalski
Quarterly No. 2, 2013 pages 135-140
DOI:
keywords: hybrid composite, glassy carbon, precursor, pyrolysis, ceramic foam, solid lubricant
abstract The new trend in designing and manufacturing machines and devices e.g. for the food and pharmaceutical as well as automotive industry, is replacing lubricating oils with solid lubricants incorporated into the surface layer of engineering materials. Incorporating solid lubricants helps decrease both the friction resistance and wear of rubbing parts as well as reduce the amount of lubricating oils to ensure efficiency and effectiveness at much lower operational costs. Moreover, the use of a solid lubricant as an additional phase in a friction material does not damage the environment by oil penetration through leaks or accumulation of waste oil residues. At the Silesian University of Technology, a novel method of obtaining a new generation composite containing glassy carbon as a solid lubricant has been developed. The uniqueness of the elaborated technology is the fact that glassy carbon is produced directly in a ceramic from a previously introduced liquid precursor. Such a solution, compared to the so far applied methods where the prepared carbon particles are mixed with the alloy matrix, appear to offer some advantages. Firstly, the manufacturing costs are lower because there is no need for the expensive procedure of mixing the reinforcing phase with the liquid metal matrix. Secondly, glassy carbon distribution throughout the entire volume of the composite is uniform, free from sedimentation or agglomeration and particles clustering. The presence of uniformly distributed glassy carbon greatly affects the tribological properties of the composite. This is possible due to the low shear resistance and high hardness as well as excessive thermal stability of the glassy carbon. An additional advantage seems to be its low thermal expansion. The friction coefficient determined during rubbing against cast iron GJL-300 in the conditions of friction in air ranges between 0.08 to 0.14.