Microstructures and wear properties of laser cladding Co-based composite coatings on Ti–6Al–4V

• New type laser cladding material system is designed with Co42, B4C, SiC, Y2O3.
• Coatings exhibiting high micro-hardness and wear resistance are fabricated.
• Too much SiC is proved detrimental to the wear resistance.
• Wear resistance is not proportional to the micro-hardness.

Metal matrix composite (MMC) coatings were fabricated on Ti–6Al–4V titanium alloy by laser cladding. Co42 self-fluxing powder, B4C, SiC and Y2O3 were employed as the cladding materials. Microstructures and the wear properties of the different composite coatings were investigated comparatively. Results showed that the laser cladding coatings were mainly reinforced by CoTi, CoTi2, NiTi, TiC, TiB2, TiB, Cr7C3 and Ti5Si3. The micro-hardness of the cladding coatings were equivalent to 3–4 times the Ti–6Al–4V substrate. Laser cladding coating exhibiting outstanding wear resistance was fabricated with the addition of 20 wt.% B4C, 7 wt.% SiC and 1 wt.% Y2O3. The wear resistance was enhanced by over 10 times compared with the substrate. However, with more SiC addition (14 wt.%), a higher micro-hardness was obtained together with poor wear resistance. The wear mechanism of the coatings was discussed by referring to the microstructures and the wear morphologies.

Schematic diagram of the laser cladding process (a) and the micro-hardness distribution of the specimens (b) [Specimen 1, Co42–20 wt.% B4C–7 wt.% SiC–1 wt.% Y2O3; Specimen 2, Co42–20 wt.% B4C–14 wt.% SiC–1 wt.% Y2O3].Figure optionsDownload as PowerPoint slide