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.

Oxidation tuning in AlCrN coatings

“…The best short-term oxidation resistance was exhibited by the AlCrSiN coating most probably due to significant grain size refinement [18]. Coating with a finer grain size has enhanced aluminum and chromium outward diffusion that leads to protective oxide layers formation [19][20][21]. At higher temperatures of oxidation (1100 °C) AlCrSiN coatings show promising oxidation resistance.…”

Hierarchical adaptive nanostructured PVD coatings for extreme tribological applications: the quest for nonequilibrium states and emergent behavior

“…Having a highly nonequilibrium state due to the formation of large numbers of lattice defects in the as-deposited state [2], the nanostructured coating possesses drastically improved mobility and reactivity of the necessary coating elements (such as Al, Si and in lesser degree Cr) at high temperatures and under heavy loads. It can transport these elements quickly (almost in an explosive-like manner) to the friction surface [266,267]. The predominant formation of protective alumina films on the surface of the nanocrystalline TiAlCrSiYN-based coatings occurs during oxidation over a wide range of temperatures from 800 to 1200…”