High temperature oxidation of powder metallurgy two phase Cu Cr alloys under low oxygen pressure

The oxidation of two phase Cu Cr alloys containing 25% and 50% Cr prepared by powder metallurgy (PM) with a rather uniform two phase microstructure has been studied at 700～900 ℃ under oxygen pressure below the stability of the copper oxides. The two PM alloys oxidized very slowly and formed only external Cr 2O 3 scales rather than undergoing an internal oxidation of chromium. This result is attributed mainly to a supply of chromium from the small Cr rich particles dispersed within the Cu rich phase. The oxidation kinetics of the two PM Cu Cr alloys approximately followed the parabolic rate law. The scaling rates are of the same order as those measured for pure chromium under the same oxygen pressure, but smaller than those for the alloys of similar composition prepared by normal arc melting techniques, whose compositions were largely non uniform. The results are interpreted in terms of the two phase nature of these alloys.

The oxidation of two-phase Cu-Cr alloys containing 25% and 50% Cr prepared by powder metallurgy (PM) with a rather uniform two-phase microstructure has been studied at 700 similar to 900 degrees C under oxygen pressure below the stability of the copper oxides. The two PM alloys oxidized very slowly and formed only external Cr2O3 scales rather than undergoing an internal oxidation of chromium. This result is attributed mainly to a supply of chromium from the small Cr-rich particles dispersed within the Cu-rich phase. The oxidation kinetics of the two PM Cu-Cr alloys approximately followed the parabolic rate law. The scaling rates are of the same order as those measured for pure chromium under the same oxygen pressure, but smaller than those for the alloys of similar composition prepared by normal are melting techniques, whose compositions were largely non-uniform. The results are interpreted in terms of the two-phase nature of these alloys.