Scaling Behavior Of Four Co-20ni-Xcr-Yal (X=8,15 Wt.%; Y=3,5 Wt.%) Alloys Exposed To 1 Atm O-2 At 1000 Degrees C And 1100 Degrees C

The oxidation of four Co-20Ni-xCr-yAl (x = 8,15 wt.%; y=3,5 wt.%) alloys in 1 atm of pure oxygen was studied at 1000 degrees C and 1100 degrees C. All the alloys formed complex scales. The alloy with lowest Cr and Al contents corroded much more rapidly than the other three materials. Incomplete external alumina scales formed only on the alloys containing 5 wt.% Al (at 1100 degrees C for Co-20Ni-8Cr-5Al and at 1000 degrees C and 1100 degrees C for Co-20Ni-15Cr-5Al). More than 5 wt.% Al is required to form continuous external alumina layers on alloys with 8-15 wt.% Cr.