Initial Oxidation Process of Ni-Nb Alloys at High Temperature—Application of High Energy Ion Backscattering Analysis for Oxidation at P_O2=40 Pa—

Abstract

The oxidation behavior of 95Ni-5Nb and 90Ni-10Nb alloys was investigated at P_O2=40 Pa and 1023 K by using the ¹⁶O ion backscattering analysis and they were compared with the preceding study of those obtained at the low pressure of P_O2=6×10⁻² Pa. The surface of each alloy was covered by either a thin smooth NiO layer or rough nodular NiO oxides. The thickness of the smooth oxide layer was measured by means of ¹⁶O ion backscattering. The formation of an internal oxidation zone was identified by the backscattering method and the X-ray diffraction analysis, etc. The thickness of this zone and the size of the internal oxide particle were determined and a considerable part of the weight gain was attributed to the internal oxidation. The internal oxide particles were identified to be mainly T-Nb₂O₅.