Steam oxidation resistance in a long term exposures of the modified Laser Power Bed Fusion 699XA alloy at high temperatures

Alloy 699 XA contains 30 wt.% Cr and 2 wt.% Al, due to presence of Cr and Al the alloy is able to develop protective oxide scale in reduced pO2 conditions. However, dearth of in depth studies on steam oxidation of 699 XA alloy, particularly in a printed state employing Laser Power Bed Fusion (LPBF) formed the basis of the current study. Here, steam oxidation performance of the 699 XA alloy developed by the LPBF process and modified version of the alloy symbolized as: MAC-ISIN-699 and MAC-UN-699-G were investigated. The MAC-ISIN-699 is the 699 XA alloy with modified alloy composition where powder underwent in-situ internal nitridation during atomization, whereas the sample MAC-UN-699-G: is also modified 699 XA alloy for gamma prime precipitation but with no modification on the powder. The alloys were exposed for 5000 hours at 750 and 950 oC in steam oxidation rig localized in KIT in Poland. The analyses of the exposed materials were carried out in KIT using SEM/EDS from the surface and the cross-sectioned samples, XRD analyses were carried out to determine phases developed during a long term exposures at high temperatures.