Films of amorphic diamond can be deposited from laser plasma ions without the use of catalysts such as hydrogen or fluorine. Prepared without columnar patterns of growth, the layers of this material have been reported to have ‘‘bulk’’ values of mechanical properties that have suggested their usage as protective coatings for metals. Described here is a study of the bonding and properties realized in one such example, the deposition of amorphic diamond on titanium. Measurements with Rutherford backscattering spectrometry and transmission electron microscopy showed that the diamond coatings deposited from laser plasmas were chemically bonded to Ti substrates in 100–200-Å-thick interfacial layers containing some crystalline precipitates of TiC. Resistance to wear was estimated with a modified sand blaster and in all cases the coating was worn away without any rupture or deterioration of the bonding layer. Such wear was greatly reduced and lifetimes of the coated samples were increased by a factor of better than 300 with only 2.7 μm of amorphic diamond.

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Four types of diamond films have been shown to be stable and free from hydrogen: crystalline diamond, amorphic diamond, i-C and defected graphite. Each is significantly harder than other forms of carbon, but only now are quantitative values of hardness being reported. In this work nanoindentation techniques were used on these highly elastic films and linear ranges of plastic response were identified. Values of hardness were extracted from the on-load data for amorphic diamond and crystalline diamond that could not be distinguished from the hardness of naturally occurring diamond. This seems to explain why thin layers of amorphic diamond have been so effective in protecting substrates from the erosive impacts of particles and droplets reported in previous studies.