On the Oxidation and Nitridation of Chromium at 1300 A°C

Chromium can be a candidate of interest as a base component for refractory alloys for high temperature applications. Few data are available about oxidation kinetic of chromium in air for temperature as high as 1300 A degrees C. Moreover, rare papers take the nitridation of chromium into account in the description of the oxidation process or in the calculation of the kinetic constants. In the present study, global methods like thermogravimetry were linked to thickness measurements and microstructural characterisation to evaluate oxidation and nitridation contribution to weight gain. High stress levels were induced in the oxide layer during its formation. The kinetic constant associated to the nitridation, at this temperature, was one order of magnitude higher than the parabolic oxidation constant. Experiments demonstrated that the presence of nitrogen in the substrate is always a precursor to breakdown of the oxide layer and does not result from diffusion through the Cr(2)O(3) layer.