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

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 2u values. The laser cladding Ti–Al coatings with 14.7 and 18.1 at.% Al were composed of a-Ti and a2-Ti3Al phases, while those with 25.2 and 29.7 at.% Al were composed of a2-Ti3Al 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