Mechanical Properties and Microstructure of Nano-crystalline AlN Coating on Mild Steel

Aluminum nitride (AlN) is a tetrahedral III-V compound which crystallizes under ambient conditions in the thermodynamically stable hexagonal quartzite structure. AlN thin films are of high importance because of their exceptional mechanical properties, thermal behavior, and optical characteristics. AlN thin films exhibit broad bandgap with a large refractive index and less absorption coefficient. They exhibit high hardness, high breakdown voltage, low dielectric constant, high electrical resistivity (~1013 Ω-cm), high piezoelectric coupling coefficient, thermal stability (2200 °C), and high thermal conductivity (~320 W/mK). It is the most used and essential material for the manufacture of piezoelectric sensors, actuators, and surface acoustic wave (SAW) devices. It also finds applications in optical devices, hard coatings, and protective coatings, etc. In this paper, an effort has been taken to determine the properties of AlN coated mild steel. The coating is done using DC magnetron sputtering. The properties such as mechanical, corrosion, and microstructure are investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), micro-indentation, and wear test, respectively