Oxidation Studies on the Nickel-Chromium and Nickel-Chromium-Aluminum Heater Alloys

Abstract

A systematic study was made of the oxidation resistance of five 80Ni‐20Cr heater alloys and one 4Al‐19Cr‐77Ni alloy. Kinetic and crystal structure studies were made over the temperature range of 500° to 1100°C. The adhesion of the oxide film to the alloy was tested by the strain oxidation technique, and the over‐all performance was evaluated by the ASTM useful life tests. The rate of oxidation of the several alloys could not be correlated with the ASTM useful life results, while the strain oxidation tests could be correlated with the ASTM useful life tests. was the major oxide formed on the 80Ni‐20Cr alloys at 1100°C. Although , and were observed below 1000°C on the 4Al‐19Cr‐77Ni alloy, no was observed in the oxide scale at 1100°C. A thermodynamic and kinetic interpretation was made of the results.