High power diode laser alloying of TiB2 and amorphous-boron with titanium: Phase, microstructure and hardness analyses

Abstract Laser alloying creates a new alloy or ceramic composite coating with improved surface properties of materials. This work has developed a hard coating by high power diode laser alloying of preplaced TiB2 and amorphous boron (a-B) layer with Cp-Ti and Ti6Al4V substrates under argon and nitrogen gas shielding, which respectively termed as laser boriding and boronitride techniques. The composite coating was investigated by X-ray diffraction, Energy Dispersive X-ray, Elemental mapping, Optical microscopy and FESEM and Vickers hardness analyses. A simple analytical equation was employed to estimate surface temperature to correlate phase formation behavior. The XRD revealed the formation of TiB2 and TiB phases in the borided surface and TiB2, TiB, Ti4N3B2 phases in the laser boro-nitrided surface. The EDAX and elemental mapping confirmed the boron and nitrogen in the laser boro-nitrided cross section. The optical and scanning electron microscopy revealed that coating predominantly consists of TiB ceramic precipitates. A high hardness in the range 1217–3351 HV0.2 was obtained in the laser borided and boro-nitrided coating cross sections, due to the formation of TiB2 and Ti-B-N phases.