NANO-CRYSTAL ALLOY AND ALLOY-OXIDE COATINGS AND THEIR HIGH-TEMPERATURE CORROSION PROPERTIES

Abstract

Nano-materials often possess special properties that materials with identical compositions but ordinary grain size do not have. This paper reports our work on the alloy and alloy-oxide nano-composite coatings. These coatings have special properties at elevated temperatures. Nano-crystal structures accelerate diffusion of certain types of elements, promoting selective oxidation of alloys, and forming desirable protective oxide films with low growth rate. The high-density grain boundaries also provide a network that holds the oxide scale tightly to the substrate, greatly improving the oxide scale spallation resistance. This paper also reports the processing techniques that are used to apply the nano-crstal alloy and alloy-oxide coatings, discuss the effects of mixed grain boundary and lattice diffusion, and studies the interface structures of oxide to metal substrate.