Phase composition and tribological properties of Ti–Al coatings produced on pure Ti by laser cladding

Abstract

Ti–Al coatings with ∼14.7, 18.1, 25.2 and 29.7 at.% Al contents were fabricated on pure Ti substrate by laser cladding. The laser cladding Ti–Al coatings were analyzed with X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray energy dispersive spectroscopy (EDS). It was found that with the increase of Al content, the diffraction peaks shifted gradually to higher 2 θ values. The laser cladding Ti–Al coatings with 14.7 and 18.1 at.% Al were composed of α-Ti and α 2-Ti 3Al phases, while those with 25.2 and 29.7 at.% Al were composed of α 2-Ti 3Al phase. With the increase of Al content, the cross-sectional hardness increased, while the fracture toughness decreased. For the laser cladding Ti–Al coatings, when the Al content was ≤18.1 at.%, the wear mechanism was adhesive wear and abrasive wear; while when the Al content ≥25.2 at.%, the wear mechanism was adhesive wear, abrasive wear and microfracture. With the increase of Al content, the wear rate of laser cladding Ti–Al coatings decreased under 1 N normal load, while the wear rate firstly decreased and then increased under a normal load of 3 N. Due to its optimized combination of high hardness and high fracture toughness, the laser cladding Ti–Al coating with 18.1 at.% Al showed the best anti-wear properties at higher normal load.