The effect of particle size of alumina dispersions on the oxidation resistance of Ni-Cr alloys

Abstract

The oxidation behavior of Ni-Cr alloys with various chromium concentrations and particle sizes of a dispersion of 10 vol.% Al2O3 was observed in 1 atm of oxygen at 1000 degrees C, This study was intended to determine the critical chromium concentration to form a protective Cr2O3 oxide layer for different Al2O3 particle sizes. The oxidation rate of Ni-Cr alloys containing 10 vol.% Al2O3 followed a parabolic rate law and a Cr2O3 protective layer continuously formed when the oxidation rate decreased rapidly. Times to form a continuous and protective Cr2O3 layer during the initial oxidation shortened as the size of the dispersion decreased The critical chromium concentration to form a protective Cr2O3 layer in the oxide scale was 6 similar to 9 wt.% and was related strongly to the particle size of the Al2O3 dispersion.