Effect of Palladium and Chromium Additions on the Oxidation Behaviour of #beta#-NiAl Alloys

摘要

Isothermal oxidation behaviour of a Pdand (Pd+Cr) #beta#-NiAl alloyed phase has beenstudied between 900 and 1200 deg C. The main effectof noble metal addition is the improvement of Aldiffusion rate, as compared to binary #beta#-NiAl alloy.This modification leads to an increase of related togrowth of #alpha#-Al_2O_3 and to a decrease of theinitial transitory periods where metastable Al_2O_3 areformed. Alloying of the #beta#-NiPdAl) withchromium suppresses the initial transition step at 1200deg C, because hexagonal (Cr,Al)_2O_3 nucleipromote probably #alpha#-Al_2O_3 formation.