Formation and Properties of Selecting Functionally Gradient Sprayed Coating by Direct Diode Laser/ Cold Spray Process

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A thermal sprayed coating is formed by the successive deposition of a stream of molten droplets through the impacting, flattening, and rapid solidification and cooling processes. In the new solid cold spray process, the coating is formed by high-velocity particles impacting to the substrate to be coated without heat. These particles bond mechanically with the substrate by way of plastic deformation only. In order to help establish innovative and cost-effective applications of plastic materials in the automotive and chemical industry as well as in medical technology, surface modification is becoming more and more important as a complement or alternative to the development of new plastic materials with specific physical and chemical profiles. Commonly, polymer surfaces are coated by metallization, to enhance tribological properties or chemical resistance and to provide electromagnetic shielding or decorative effects. Examples for industrial surface refinement techniques are chemical coating, ion implantation and thermal spray coating.In this study, the performance of a newly developed solid cold spraying apparatus and the photo-catalytic properties of TiO_2-Zn coatings were examined. TiO_2-Zn coatings were post-treated by direct diode laser and examined its mechanical properties in compare with that formed by solid cold spray process. The photo-catalytic properties of laser treated TiO_2-Zn coatings on a plastic substrate were equivalent to that of cold sprayed TiO_2-Zn coatings. We treated Cr_3C_2 coatings by laser irradiation treatment and examined its hardness in comparison with that formed by HVOF process. Consequently, the average hardness of laser treated Cr_3C_2-NiCr coating was found out to be higher than that of HVOF coatings. The laser treated Cr_3C_2-NiCr coating further improved the solid particle erosion resistance by a factor of almost twice.