Nano-structured alloy and composite coatings for high temperature applications

Abstract

Nano-structured materials often possess special properties that materials with identical compositions but ordinary grain size do not have. This paper reports our work on the surface nano-crystallisation and nano-structured alloy and composite coatings. A number of processing methods including magnetron sputtering, thermal spray and pulse electro-spark deposition have been used to produce surface nano-crystalline structure. The compositions and microstructures can be well controlled by using different targets or electrodes, nano-structured composites and adjusting processing parameters. Surface nano-structured coatings can provide special chemical, mechanical and electronic properties such as high temperature corrosion and corrosive wear resistance. It has potential applications such as turbine blades, engine parts for petrochemical, aerospace and electronic device industries. This paper is focused on the study of the interrelations between processing, microstructure and properties. Physical models have been established to explain the effects of nano-crystalline structure on the properties.

Microstructure and transformation of Al-containing nanostructured 316L stainless steel coatings processed using spark plasma sintering

“…In that study, for the tested temperatures of 500, 800 and 1000 • C, the nanocrystalline 316LSS-6 wt.% Al powders showed lower weight gain and better oxidation properties than conventional 316LSS powders. They also demonstrated that at 500 and 800 • C, the weight gain of the nanostructured powders was almost half that of the micron-sized powders while the weight gain was seven times lower for the nanocrystalline 316LSS-6 wt.% Al powder tested at 1000 • C. In addition, three independent studies, performed by Almathami et al (2008), Wang (1997) and Gao and Li (2004), have all shown that for smaller grain size materials possessing an increased number of diffusion paths, the formation of the protective ␣-Al 2 O 3 scale at elevated temperatures in nanograined Al-containing alloys occurs at lower Al concentrations than for the same alloy with micron-sized grains.…”

Study and Computational Simulation of Nanomaterial Coating to Reduce Crevice Corrosion

“…Currently the nano-coating is an effective corrosion-resistant technology applied to many fields because of its superior corrosionpreventive property. Nanomaterial structure has its extremely small grain size and large grain boundary ratio with strong protective oxide scale that is firmly adhesive to the substrate of coated material with outstanding wear, scratchresistant, and water-resistant properties [11,12]. Nano-coating structure combines superior material strength and ductility.…”

The effect of grain boundary engineering on the oxidation behavior of INCOLOY alloy 800H in supercritical water

“…Moreover, the smaller hematite grain size on GBE-treated samples as shown in Fig. 6 could alleviate growth stress buildup [24] and thus benefit spallation resistance.…”