Laser surface alloying of a titanium aluminide alloy for Al₂O₃/TiAl wear resistant composite coatings

Laser surface alloying using nickel-clad Al₂O₃ powder pre-coatings is employed to improve the wear resistance of a γ-TiAl intermetallic alloy Ti-48Al-2Cr-2Nb. An 'in-situ' wear resistant γ-TiAl matrix composite coating reinforced by rapidly solidified Al₂O₃ particles is fabricated on substrate of the γ-TiAl intermetallic alloy. The distribution of the Al₂O₃ reinforcing phase throughout the laser surface alloyed Al₂O₃/TiAl composite coating is uniform except in the transition zone to the substrate where the coating's microstructure exhibits strong gradient characteristics. The bonding of laser surface alloyed coating to the substrate is of high quality metallurgical. Cracking of the laser surface alloyed coatings can be completely eliminated by preheating and post treatment slow-cooling. Both hardness and wear resistance of the γ-TiAl intermetallic alloy are significantly enhanced after laser surface alloying treatment.