The effects of uncommon silicides on the oxidation behavior of alloys from the Nb–Cr–Si system

The effect of Si on the oxidation resistance of the Nb-20Cr-(10-42)Si alloys has been studied. The major contribution of Si is to produce Nb5Si3 phase which enhances oxidation resistance and the high temperature strength. A range of Si from 10 to 42 at.% allows for the determination of microstructural stability especially for the silicides and Laves phases (NbCr2). It has been observed that the weight gain per unit area is lower with increased Si concentration. There may be other silicides besides Nb5Si3 which may be contributing to the oxidation resistance. Characterization has been performed using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) in EDS, BSE and X-ray mapping modes. A comparison between the theoretically expected and experimentally observed micro-constituents has been made.

► Nb-20Cr is tested under oxidation with Si ranges of 10, 20, 30, and 42Si.
► Temperatures tested range between 700 and 1400 °C in 100 increments.
► Uncommon silicides were characterized via SEM, XRD, and EDS.
► Improved oxidation resistance is reported with high concentrations of Si.