ENVIRONMENTAL-EFFECTS DURING APPLICATION OF MATERIALS AT TEMPERATURES ABOVE 1200-DEGREES-C

The materials which may have properties for use at temperatures above 1200-degrees-C are examined and shown to be some refractory metal alloys, a few intermetallics, a number of ceramics, and composites. It is shown that the most important form of environmentally induced degradation of these materials at temperatures above 1200-degrees-C is oxidation. The oxidation of each of these types of material is then examined. It is shown that, in order for materials to possess adequate oxidation resistance at temperatures above 1200-degrees-C, external scales of Al2O3 or SiO2 must be formed as reaction products.