High Temperature Alloys from Nb-Cr-Si System with Minor Additions
|Periodical||Materials Science Forum (Volumes 654 - 656)|
|Edited by||Jian-Feng Nie and Allan Morton|
|Citation||Benedict Portillio et al., 2010, Materials Science Forum, 654-656, 570|
|Online since||June, 2010|
|Authors||Benedict Portillio, David Alvarez, Alma Vazquez, Shailendra K. Varma|
|Keywords||EDS, Nb Alloy, Oxidation, Pesting, Scanning Electron Microscope (SEM), Spallation, X-Ray Diffraction (XRD)|
Several Nb based alloys (Nb-20Mo-15Si-25Cr, Nb-20Mo-15Si-25Cr-5B, Nb-20Si-20Cr-5Al, and Nb-20Cr-20Si-5Hf) have been prepared to evaluate the oxidation resistance from 700 to 1400ºC in air. The phase identification was determined by calculating the isothermal sections in this temperature range using PANDATTM software. The experiments involve static heating for 24 hours (short term oxidation, STO) or 7 cycles of 24 hour heating (long term oxidation, LTO). Weight gain per unit area as a function of either temperature (STO) or time (LTO) has been used to determine their oxidation resistance. However, SEM, EDS on SEM, x-ray mapping, and XRD have been used to evaluate the oxide scale characterization and the influence of various microconstituent effects have been determined. It appears that B addition may be beneficial while Al is advantageous in comparison to Hf addition. The problem of pesting, typically, in a range of temperature from 900 to 1100ºC needs to be controlled through minor additions since the alloys exhibit fairly good resistance at lower and higher temperatures up to 1400ºC.