Synergistic effects of surface micro-crystallisation and ce addition on selective oxidation of Ni-20Cr alloy

Surface micro-crystalline coatings were prepared on Ni-20Cr and Ni-20Cr-Ce alloys by high-energy pulse plasma treatment (HEPP). After oxidation at 100 0 degrees C in air for 200h, it was shown that both oxidation resistance an d the Cr content in the oxide scales on these four alloys increased in the order of Ni-20Cr < Ni-20Cr-Ce < Ni-20Cr (HEPP) < Ni-20Cr-Ce (HEPP). The res ults indicated that the selective oxidation of Cr in Ni-20Cr alloys can be improved either by adding Ce or surface micro-crystallisation. The synergis tic effects have been discussed based on Wagner's selective oxidation theor y, together with the reactive element effects, short circuit diffusion, oxi de nucleation and growth processes, and stress release in the oxide scales.