Abstract
Chemical vapour deposition of chromium on the surface of low-carbon iron alloys has been investigated using a novel CVD method that combines the low cost of pack metallisation with the advantages of vacuum technique. Chromizing processes have been carried out in a hot-wall vacuum oven with a mass spectrometer to determine the chemical composition of residual gases. The processes have been performed in chromium chlorides atmosphere at a low pressure range from 1 to 800 hPa, the treatment temperature 800 to 950°C. The effect of the vacuum level during the process and the process parameters such as time and temperature on the growth kinetics of diffusion layers has been determined. Studies of layer thickness, its morphology, its phase composition, Cr and Fe depth profiles in the diffusion zone of chromized layers have been conducted. The investigations have proved that the chromizing process under low pressure, with static vacuum instead of dynamic vacuum conditions during the holding is the most effective as far as the growth kinetics of diffusion layers is concerned. It has been shown that the kinetics of the process is controlled by the diffusion of chromium in the steel.
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