An investigation into the fabrication and properties of Ni 3Al thin coatings on nickel substrates

Abstract

Thin film intermetallic aluminides are being studied for use as interconnects in microelectronics, working coatings in alloys and matrix in composite materials because of their good corrosion resistance, low oxide inclusions and high bond strength with substrates. In aerospace applications, nickel-base superalloys are being used in turbine blades which operate as temperatures u to 1000 C or higher. Their main requirements are corrosion and oxidation resistance, high temperature strength, and resistance to thermal shock and fatigue. One obvious way to improve the resistance to corrosion and surface wear of superalloy blades at high temperatures is to apply protective coatings on the blades. In this respect, it is well known that the intermetallic compound Ni{sub 3}Al possesses advantageous high-temperature properties. It exhibits the so-called flow stress anomaly, which means that the strength of the material gets higher as temperature increases up to about 650 C. It is also interesting to note that Ni{sub 3}Al and nickel share similar physical properties such as thermal expansion coefficients and melting temperatures. Together with their equivalent fcc lattice structures and low theoretical lattice mismatch (1.3%) at their interface, a Ni{sub 3}Al intermetallic thin film is therefore expected to exhibit excellent adhesion with a supporting Nimore » substrate, while providing the latter with improved resistance to mechanical wear, chemical corrosion and high temperature oxidation. On this consideration, the aim of this work is to synthesize Ni-Al thin films with the 3Ni/1Al stoichiometry by the sputter technique on nickel substrates and to study the oxidation and wear resistance of the Ni{sub 3}Al coating-nickel substrate system.« less