Bottom-up Synthesis of Nanocrystalline Intermetallic Coatings with Controlled Microstructures

Arizona State University, Scottsdale AZ

Investigators

Abstract

Coatings made of metallic alloys are used in a wide range of industries from machine tools to automobiles, aircraft and thermal power plants. These coatings increase resistance to wear, corrosion and oxidation and enhance the performance of structural and functional components to which they are applied. Thus, the ability to tailor the properties of metallic alloy coatings would lead to significant improvements in the efficiency and lifetime of automobile and aircraft engines, cutting tools and power plant turbines and tubings. This award supports fundamental research that aims to control the microstructure (size, shape and distribution of small-scale crystallites) of metallic alloy coatings. Since the mechanical, chemical and thermal properties are intimately connected to the microstructure, this would allow the PIs to tune the properties of the coatings for various applications. The research activity is integrated with education and outreach efforts that include a mentoring program for undergraduates, scientific demonstrations for high school students and training of graduate students in materials synthesis and characterization. Current methods to synthesize metallic alloy coatings using either chemical or physical deposition processes provide only limited capability for controlling the microstructure. This project aims to develop a new bottom-up process to synthesize intermetallic coatings with tailored microstructures using physical vapor deposition. The central hypothesis of the project is that by methodically seeding nanocrystals during the growth process, amorphous intermetallic coatings can be controllably crystallized during subsequent annealing at the appropriate temperature. The project will elucidate the fundamental physics of this process and demonstrate its practical viability by synthesizing and characterizing nanostructured titanium aluminide (TiAl) coatings with controlled grain size, aspect ratio and spatial distribution. In addition, microstructural evolution, stability and mechanical behavior of the synthesized TiAl coatings will be investigated using in situ transmission electron microscopy and X-ray diffraction experiments to understand the crystallization kinetics and structure-property relationships.