Effect of the annealing temperature and the thickness of carburizing layer on the obtained chromium carbides

Abstract

Low carbon steel substrates were surface hardened by carburizing in solid medium, and then thin layers of chromium were deposited by electrolytic way. After chromium deposition, the samples were exposed to isothermal annealing at temperatures between 500 and 1100 °C for 1 and 2 hours duration. The obtained thin layers were characterized by X-rays diffraction, optical microscopy and Vickers micro-hardness.

The obtained results showed that chromium layers are transformed into chromium carbide by metastable phases of transition. At 500 °C annealing temperature thin films retain their monophasic character Crα, and they almost keep the same hardness values. When temperature range is between 700 and 900 °C the incipient phase appears and is increased while the chromium mother phases decrease. After annealing at 1100 °C, the chromium layer is completely converted into chromium carbides that would be responsible for the increase of the hardness and adhesion layer / substrate.