The Effect of Aluminizing Nb Refractory Metal Surface on Increasing Oxidation Resistance

Abstract

In order to increase oxidation resistance of Nb refractory metal, Aluminizing and Aluminizing + Siliconizing with co-deposition were applied to its surface through the method of Halide-activated pack cementation (HAPC). The characterization of diffusion coating was conducted via the analyses of SEM, XRD, and EDS. After that, oxidation tests were conducted, and the effect of coating on oxidation resistance was examined. As a result, according to XRD analysis, it was found that there were Nb5Si3 phase structures in both coatings. In addition to this, Nb5Si3 and Nb3Si phases emerged in co-deposition coating. Protective NbSi2 phase was not observed because an activator with fluoride was used but an activator with chloride was not. Both methods increased the oxidation resistance of Nb. However, it was observed that the target value which was “metal loss of 25μm at 1300°C 100 hours after oxidation” was not obtained only through cementation aluminizing process. We are indebted to TUBITAK for their support.

Keywords: Refractory metals, oxidation, pack cementation, co-deposition, aluminizing

DOI: 10.7176/JSTR/5-10-12