Synthesis And Characterization of Titanium – Aluminum Intermetallic Hard Coatings By Sputtering

Abstract

The titanium – aluminum intermetallics are extensively used in aerospace applications. Such materials systems basically consist of different percentage of titanium and aluminum. The characteristics of a given phase depend on percentages of titanium and aluminum. When titanium – aluminum are coated on the bulk materials in thinfilm forms, oxidation resistance, wear resistance, and surface hardness of the material improve to suit particular applications. Hence the work concentrates on the development of hard intermetallic coatings suitable for aerospace applications by reactive co-deposition of titanium and aluminum using unbalanced dc magnetron sputtering in oblique angle mode. The process parameters were optimized to obtain high quality uniform films. Thin films were deposited on glass, copper, aluminum, alumina and mild steel substrates for different types of characterization. The materials developed by the above-mentioned root were studied in detail with greater emphasis on its phase formation, texture, microstructure evolutions and oxidation resistance. The characterization of deposited films was done using X-Ray diffraction, scanning electron microscopy with energy dispersive spectroscopy, atomic force microscopy microhardness and nanohardness measurements. The XRD characterization carried out confirmed growth of intermetallic TiAl. The crystal structure of the grown film was found to be orthorhombic. This analysis revealed the crystallite size of 123.7Å with lattice strain of 0.1352. Also it was found to be in gamma region of Ti – Al phase diagram. The scanning electron microscopy study revealed continuous columnar growths of the film on to the substrates. There was a good adherence of the films to the substrates. The heat treatment study carried out in the temperature regions of 400°C to 1200°C showed decrease in crystallite size with increase in the lattice strain due to the formation of TiO2 and Al2O3. The microhardness and nanohardness studies carried out showed a value of 18.34 GPa and 36.3GPa respectively and values are found to be in accordance with the literature.Synthesis and Characterization of Titanium – Aluminum Intermetallic Hard Coatings by Sputtering.