Effect of Cr and Zr addition on oxidation resistance of nanocrystalline Fe-Cr-Ni-Zr

Abstract

The effect of nanocrystalline grain size and alloying additions of Cr, Ni and Zr on the oxidation resistance of nanocrystalline Fe-based alloys has been investigated. Bulk nanocrystalline alloy pellets, having composition Fe-xCr-5Ni-2Zr and Fe-xCr-5Ni {x = 7, 10} were prepared by a mechanical alloying and compaction route. A novel multi-step hot-compaction process has been investigated for the consolidation of powders into close-to-100% dense nc pellets (grain size 60-70 nm). The pellets showed high hardness (7.5-8.0 GPa) and reasonable ductility under shear stress condition. The high temperature oxidation resistance of these alloys, at 550 °C, has been compared with conventional microcrystalline stainless steel alloy. Nanocrystalline grain size was found to improve the oxidation resistance particularly in the alloys with lower Cr content. This behaviour is attributed to the greater grain boundary diffusivity of Cr in the nanocrystalline alloys. Zr addition was found to improve the thermal stability and insignificantly influence the oxidation resistance. © 2011 Australasian Corrosion Association