Hardness and grain size relations for thick chromium films deposited by hallow cathode discharge

Chromium films deposited by hollow cathode discharge show a variety of hardness, wear resistance and anti-corrosion characteristics. To find the relation between these properties and the film structure, investigations using X-ray diffraction, transmission electron microscopy and Auger electron spectroscopy were carried out for a variety of substrate bias voltages.Films deposited by hollow cathode discharge at 190°C and biased at 0 V and ?50 V and an electrochemically plated hard chromium film were compared by measurements of the Vickers microhardness and the line broadening of the (222)Cr line of X-ray diffraction after vacuum annealing at several temperatures. The hardness is approximately proportional to the square root of the line broadening.All the deposited films show a similar relation between hardness and line broadening. The square root of the grain size of these films as observed by TEM is inversely proportional to the hardness. This relation supports an empirical equation obtained by Agarwal et al. who worked with vacuum-deposited NiCr films. The grain size of the films as observed by TEM is several times larger than that calculated from line broadening.