Ceramic Coating of Titanium by Pulsed YAG Laser(Physics, Process & Instrument)

概要

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With the object of improving erosion and wear resistance of titanium (Ti), a feasibility of the formation of hard ceramics such as carbides, borides and nitrides on its surface was investigated by irradiating powder-predeposited Ti sheet with a pulsed YAG laser under argon (Ar) or nitrogen (N_2) atmosphere. As a result, a flat surface of laser-melted zone was formed depending on a proper amount of powders under appropriate laser irradiation conditions, and the fusion zone generally exhibited a dendritic microstructure (with some inclusions in the case of boron or boride powders). The analyses of X-ray diffractometer results confirmed that carbides, borides and nitrides were formed in addition to alpha-Ti phase in the vicinity of the surface, and probably constituted the dendrites in the fusion zone. Vickers surface hardnesses of fusion zones measured under 100g load were increased and varied in the range of about 500 to 1200kg/mm^2 in Ar atmosphere and about 1000 to 1700kg/mm^2 in N_2 environment, although Ti sheet had a hardness of about 200 to 250kg/mm^2. Hence, the utilization of N_2 atmosphere instead of Ar during laser irradiation increased the surface hardness of about 500kg/mm^2 for powder compositions such as C, TiC, WC, SiC, B and TiB_2. Some inclusions in boride coatings indicated hardness values of more than 2000kg/mm^2.
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