Fabrication of Ti–Al coatings by mechanical alloying method

By means of the mechanical alloying (MA) method, Al and Ti+Al coatings were deposited on Ti alloy substrates. During the mechano-activation processing, the substrate surface was impacted by a large number of flying balls along with particles of powder. The repeated ball collisions with the substrate resulted in the deposition of powder on its surface. MA technique produced Ti+Al coating with a thickness of 200 μm and Al one with a thickness of 50 μm after 2 h milling at room temperature. The as-synthesized coatings showed structures with high apparent density and free of porosity. The surface morphology of the MA-coatings was very rough. Annealing treatment led to the leveling of this uneven morphology. Annealing at temperatures ranging between 600 °C and 1100 °C gave different aluminide phases on the samples. In the case of Al coating, Al3Ti and Ti3Al compound were observed upon heating up to 1100 °C. In the case of Ti+Al coating, Al3Ti, Al2Ti, TiAl and Ti3Al were formed on the surface.