Microstructural characteristics, crack frequency and diffusion kinetics of functionally graded Ti-Al composite coatings: Effects of Laser Energy Density (LED)

Abstract

This study examines the dependence of microstructural characteristics, crack frequency and diffusion kinetics of functionally graded (FGM) titanium aluminide coatings reinforced with TiC on laser energy density (LED). Samples deposited on a Ti-6Al-4V substrate via single-step laser cladding (LC) were characterised with an optical microscope, scanning electron microscope/energy-dispersive x-ray spectroscopy and x-ray diffraction. LED set at 17.50 J/mm2 induced a thermo-positive reaction between FGM constituents, which resulted in the formation of intermetallic compounds (e.g., Ti2AlC, and a2 matrix phases) with a microhardness greater than that of the substrate and least crack frequency. Variation in microhardness across the layers of sample fabricated with 17.50 J/mm2 is attributed to diffusion kinetics strongly influenced by laser-materials interactions due to the differing chemical composition across its volume. These outcomes provide guidance for a future study that engages the substrate’s pre-heat temperature in eliminating microstructural defects via a low-cost and time-effective single-step LC process.