Hard amorphous silicon carbonitride coatings produced by plasma enhanced chemical vapour deposition

Hard amorphous silicon carbonitride coatings for wear resistance have been produced by d.c. plasma-enhanced chemical vapour deposition on pure iron at 573 K. Compared with most plasma assisted processes work was conducted under a relatively high pressure of 130 Pa. The advantages of this technique are an amorphous film structure, high deposition rates (up to 2 mum/min), high hardness and simple equipment. Hexamethyldisilazan (HMDSN) was used as precursor and argon, hydrogen, nitrogen and ammonia as process gases. The dependence of the coatings on the process parameters (process gas and d.c. power) was investigated. The characterization of the samples was carried out mainly by Fourier transform infrared spectrometry (FTIR), electron probe microanalysis (EPMA) and hardness measurement. Samples show clearly the infrared spectra absorption bands characteristic of SiC and Si3N4, with traces of hydrogen bonding. The material structure shows a strong dependence on the process gas and the d.c. power. However, for argon and hydrogen were deposited carbon-rich SiC films with low nitrogen content. Nitridic films with low carbon content were deposited using nitrogen and especially ammonia. The hardness of the produced coatings was about 10-55 GPa.