Novel physical vapour deposited coatings for complex shaped cutting tools

Abstract

The C60 thin film deposited on steel substrate was transformed by high pressure–high temperature treatment to a superhard and superelastic material. The films were studied by Raman spectroscopy in situ at 20 GPa after heating at 300°C and ex situ after the quenching. The hardness and elastic properties of the high-pressure phases have been characterized with nanoindentation. The hardness of the films were determined to be 0.5±0.1 GPa and 61.9±9 GPa for unmodified C60 and HPHT treated films, respectively. The hardness of the pressurized film is higher than for cubic BN but lower than hardness values reported for ultrahard fullerite samples prepared from powders. An interesting observation was that the HPHT treated film showed an extreme elastic response with an elastic recovery of approximately 90%.