Oxidation of additive manufactured 699XA Ni-based alloy under different atmospheres

The oxidation behaviour of an additively manufactured (AM) NiCrAl alloy (VDM® Powder 699XA) was compared with the hot rolled counterpart in different atmospheres (dry air, Ar-10 %H2 and Ar-10 %H2-10 %H2O) for 48 h at 950 and 1100°C. Internal oxidation occurred through the twin boundaries and dislocations in the AM material. Such defects promoted the outward diffusion of Al and the growth of a protective Al2O3 scale at reduced PO2 (Ar-10 %H2 and Ar-10 %H2-H2O), hence restraining the internal oxidation. It is thus demonstrated that this high Cr-containing alloy is a marginal alumina former under controlled conditions like the hot rolled alloy.