USING LASERS TO FABRICATE COATINGS ON SUBSTRATES

摘要

Laser energy is directed at a substrate to mobilize, vaporize and react a constituent (primary) element (e.g., carbon) contained within the substrate, so as to modify the composition (e.g., crystalline structure) of the constituent element, and to diffuse the modified constituent back into the substrate, as an adjunct to fabricating a coating (e.g., diamond or diamondlike carbon) on the surface of the substrate. This creates a conversion zone immediately beneath the substrate, which transitions metallurgically from the composition of the underlying substrate to a composition of the coating being fabricated on the surface of the substrate, which results in diffusion bonding of the coating to the substrate. Additional (secondary) similar (e.g., carbon) or dissimilar elements may be introduced in a reaction zone on and above the surface of the substrate to augment the fabrication of and to determine the composition of the coating. The laser energy is provided by a combination of an excimer laser, and Nd: YAG laser and a CO2 laser, the output beams of which are preferably directed through a nozzle delivering the secondary element to the reaction zone. The reaction zone is shielded by an inert (non-reactive) shielding gas (e.g., N2) delivered through the nozzle. A flat plasma is created by the lasers, constituent element and secondary element on the surface of the substrate and the flat plasma optionally extends around the edges of the substrate to fabricate a coating thereon. Pre-treatment and coating fabrication can be performed in conjunction with one another (insitu). Alternatively, a substrate can be pre-treated to characterize its surface for subsequent coating. In either case, certain advantageous metallurgical changes are induced in the substrate due to the pre-treatment. The processes (pre-treatment and coating fabrication) are suitably performed in ambient, without preheating the substrate and without a vacuum. Substrates of numerous geometries, sizes and shapes, such as flat cutting tool inserts as well as round cutting tools, are readily coated in this manner. The lasers are directed at any suitable angle (including coaxial) relative to the substrate and/or the plasma.