High Temperature Oxidation of Chromium-Nickel Steels

The scaling of austenitic stainless steels Type 302, 309 and 330 has been investigated by weight gain vs time measurements in air at 1600 to 2000 F and subsequent examination of the scales. As had been found previously with chromium steel, the curves exhibit breaks indicating intermediate periods of rapid oxidation due to disruption of the protective scale layer. Accumulation of silica at the metal/scale interface is found to contribute to this disruption; voids are considered to have the same effect. A distinction is drawn between such breaks and the type which arises from the extraordinary protectiveness of an initial thin oxide film, which is markedly affected by surface preparation and prior treatment. 3.2.3