Reinforced TiAl-Based Alloy Coatings Prepared by Laser Melting Deposition

TiAl-based alloy coating produced by laser melting deposition exhibits excellent properties of high temperature and corrosion resistance and has a wide application potential across many fields. However, the wear resistance of the coating is poor, which limits its long-term usage in harsh and complex working environments. In this study, TiB 2 reinforced TiAl-based alloy composite coatings are prepared by laser melting deposition to improve their wear resistance, and a theoretical reference for further exploring the applications of TiAl-based alloy composites in surface engineering is presented. TiAl-based alloy coatings with different TiB2 contents (0, 10%, 20%, 30%, mass fraction) were prepared on the surface of TC4 alloy using the laser melting deposition process. The effects of TiB2 content on the microstructure and mechanical properties of the coatings were systematically studied using XRD, OM, SEM, microhardness tester, indentation method, wear tester, and laser confocal microscope. Planar, columnar, and equiaxed crystal distributions were observed along the thickness direction from the bottom. With an increase in TiB2 content, the height of columnar crystal gradually decreased. TiB2/TiAl composite coatings are composed of a TiAl alloy matrix phase (gamma + alpha(2)) and a TiB2 enhanced phase. Most of the directly added TiB2 particles do not melt, but the outer layer of the directly added TiB2 particles dissolves within the molten TiAl alloy, following which primary and secondary TiB2 are precipitated in situ. The primary TiB2 has a particle form and the secondary TiB2 has a needle or flake form. With the increase of TiB 2 content from 0 to 10%, the matrix of the coating is noticeably refined, but an increase in TiB2 content (20% and 30%) do not produce further refinement. With the increase of TiB2 content from 0 to 30%, the surface hardness of the coating increases from 530.5 HV to 738.4 HV, the fracture toughness decreases from 7.75 MPa center dot m(1/2) to 3.17 MPa center dot m(1/2), the wear rate decreases from 3.98 mg/mm(2) to 0.42 mg/mm(2), and the wear degree and roughness of the wear surface also decrease. Furthermore, the wear mechanism of the coating without TiB2 is mainly microscopic cutting, supplemented by multiple plastic deformations. When the mass fraction of TiB2 is 10%, the wear mechanism of the coating is mainly microscopic cutting, supplemented by microscopic fracture. As the TiB2 content increases, the wear mechanism gradually turns to microscopic fracture. When the mass fraction of TiB2 is 30%, the wear mechanism of the coating is mainly microscopic fracture, supplemented by microscopic cutting.