Authors: Y Yamamoto ML Santella MP Brady H Bei PJ Maziasz
Publish Date: 2009/06/16
Volume: 40, Issue: 8, Pages: 1868-1880
Abstract
The hightemperature creep properties of a series of aluminaforming austenitic AFA stainless steels based on Fe20Ni1214Cr254Al0233Nb01C weight percent were studied Computational thermodynamics were used to aid in the interpretation of data on microstructural stability phase equilibria and creep resistance Phases of MC M mainly Nb M23C6 M mainly Cr B2 βNiFeAl and Laves Fe2MoNb were observed after creeprupture testing at 750 °C and 170 MPa this was generally consistent with the thermodynamic calculations The creep resistance increased with increasing Nb additions up to 1 wt pct in the 25 and 3 Al wt pct alloy series due to the stabilization of nanoscale MC particles relative to M23C6 Additions of Nb greater than 1 wt pct decreased creep resistance in the alloy series due to stabilization of the Laves phase and increased amounts of undissolved coarse MC which effectively reduced the precipitation of nanoscale MC particles The additions of Al also increased the creep resistance moderately due to the increase in the volume fraction of B2 phase precipitates Calculations suggested that optimum creep resistance would be achieved at approximately 15 wt pct Nb in the 4 wt pct Al alloy seriesThe authors thank EP George CT Liu and JH Schneibel for helpful comments on this manuscript This work was funded by the United States Department of Energy USDOE Fossil Energy Advanced Research Materials program The Oak Ridge National Laboratory is managed by UT–Battelle LLC Oak Ridge TN for the USDOE under Contract No DEAC0500OR22725 The authors also acknowledge the SHaRE User Facility at the Oak Ridge National Laboratory sponsored by the USDOE Office of Basic Energy Sciences Division of Scientific User Facilities
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