Electrochemical Assembly of Ni – xCr – yAl Nanocomposites with Excellent High-Temperature Oxidation Resistance

Abstract

Various amounts of Cr and Al nanoparticles were electrochemically assembled into a nanocrystalline Ni matrix template to form nanocomposites (, in weight percent). By characterization of the steady-state oxide scales formed at in air, an oxide map correlating the scale types with the composition ranges of the nanocomposites was established, showing that these nanocomposites can transform from NiO formers to chromia or alumina formers, by increasing the amount of to a critical, particle-size-dependent value and by changing the value of the ratio . The nanocomposites, in comparison to ternary composites assembled using Cr and Al microparticles instead of the nanoparticles and with conventionally coarse-grained alloys of similar composition, exhibited a greatly increased ability of thermally developing chromia or alumina scales. A model for the establishment of various oxide scales on the nanocomposites is proposed, correlating the nature of the scales with their specific microstructures and with the values of and .