Microstructure and mechanical properties of hard carbon films prepared by heat treatment of a polymer on steel substrate

Hard carbon films were prepared on steel substrates by heat treatment of a polymer-poly(phenylcarbyne) at various temperatures in an Ar atmosphere. The influence of heat treatment temperature on the microstructure, surface roughness and mechanical properties of the resulting films was investigated by Raman spectroscopy, atomic force microscopy (AFM), nanoindenter, scratch and ball-on-disk sliding tests. The sp2 C fractions of the hard carbon films and the root mean square (RMS) roughness increased as the heat treatment temperature increased. The preparation at 800 °C gave rise to carbon films with the maximum hardness and the hardness dropped with the higher temperature due to graphitization. In addition, with increasing heat treatment temperature, critical load of the carbon films, the ability of friction reduction and wear resistance increased gradually. The influence of the heat treatment temperature on the mechanical properties of the hard carbon films is discussed in combination with the structural analysis.