High-temperature oxidation behavior of chromium: Effect of different batches

The isothermal and cyclic-oxidation behavior of three different batches of commercial chromium (purity > 99.9%) at 900 and 1000 degreesC has been inve stigated by means of conventional thermogravimetry and thin-layer activatio n, Two hatches with a similar microstructure and one, with a five times lar ger average grain size, were used Isothermal-oxidation experiments were per formed in synthetic air for 150 hr. Cyclic-oxidation experiments were execu ted in static laboratory, air with each cycle corresponding to a period of I hr at test temperature and IZ min at ambient temperature up to a maximum of 3000 cycles. Results showed significant differences between the oxidatio n behavior of chromium derived from the three differ ent hatches. This was found under isothermal as well as under cyclic-oxidation conditions, especi ally at 1000 degreesC. The mass-loss rates during cyclic oxidation for the different hatches differed up to move than 30 times at 1000 degreesC. In ad dition, the complementary nature of the different specimen-evaluation techn iques, i.e., conventional thermogravimetry and thin-layer activation in cyc lic oxidation is shown.