Effect of substrate surface ion bombardment etching on reaction between chromium thin films and steel substrates

Thin coating films of transition metal carbides and nitrides are used because of their refractory characteristics and good mechanical properties. In this work we study the interaction between chromium thin films and steel substrates 100C6 type (AFNOR norms) containing approximately 1 wt.% of carbon. Chromium films are deposited at 200 °C by magnetron sputtering. In order to study the correlation between the pre-cleaning of substrates and the properties of coatings, two series of samples were prepared; the first is distinguished from the second by ion bombardment etching before chromium deposition. The study is carried out by X-ray diffraction, Auger electron spectroscopy, scanning electron microscopy and Vickers micro-hardness measurements. The changes observed in sample characteristics after heat treatments are associated with carbon and iron diffusion and with carbide formation. It is established that the micro-hardness of the first series is higher than that of the second series. This large difference is due to substrate etching, as induced by surface ion bombardment.