We investigate the sprayability of various hard metal and composite powder coatings via kinetic spray on cast iron by utilizing both powder and substrate preheat. These coatings include copper, a copper-zirconia composite, nickel, a zinc-nickel composite, and Ti6Al4V alloy. Using the kinetic spray process the coatings were applied to a cast iron substrate which was ground and sand blasted prior to spray. Analysis performed on powders and coating includes: cross-sectional microscopy, hardness of powders and substrate, substrate temperature as a function of heating and cooling times, and adhesion at the coating/substrate level. Results include spray parameters to allow for nickel and copper coatings to be developed on cast iron, adhesion strength as a function of powder hardness, porosity of nickel and Ti6Al4V coatings, and incorporation rates of zirconia in a copper matrix on cast iron. This is an attempt to spray hard powders on a hard substrate. Harder particles are more difficult to spray because they require more energy to plastically deform. Therefore the hardness of the particles plays a significant role in the deposition of a coating. Similarly, harder substrates are more difficult to spray on. This work demonstrates techniques that make spraying hard particles on hard substrates possible.

This paper presents a novel approach to metallize plastic surfaces. The approach has the ability to control the electrical resistance of a metallized surface by selecting the appropriate high-melting temperature metal or alloy to be thermally sprayed. Early stages of this study concluded that twin-wire arc thermal spray of high melting temperature metals do not form continuous adhering coatings on plastic surfaces. In addition, kinetic spray deposition of metals such as copper and tin on plastic surfaces also did not provide continuous uniform metallic coatings except on a few selected plastics such as Ryton and Ultem. Rather, the kinetic sprayed particles become embedded and isolated within the plastic substrate surface when using appropriate spray conditions. By combining the kinetic and thermal spray processes we developed a novel approach to metallize plastics. The kinetic spray process is used to prepare the plastic surface with anchoring sites to later accept thermally sprayed high-melting temperature metals or alloys that provide the metallization.

The kinetic spray process is a coating process that involves impingement of a substrate by metallic particles at high velocities. In this work, we investigated the kinetically sprayed Ti coatings, which were deposited onto different metallic substrates using gas-atomized powders. The powder particles were characterized in terms of size distribution, morphology, hardness, and explosibilty index. The propellant gas used for coating deposition was compressed nitrogen. The substrates were placed inside an enclosure filled with nitrogen gas during deposition. It was observed that Ti coatings can be deposited at relatively high deposition efficiencies using large particles (median size~ 100 mm). Ti coatings with a wide range of thickness and good macroscopic appearance were readily prepared. The particle temperature appears to have strong effects on the coating formation; deposition efficiencies of ~90% were achievable. Microscopic examination of the coatings revealed deposited Ti particles with significantly lower deformation when compared to ductile materials such as Al and Cu. As a result, the Ti coatings exhibited a high degree of porosity. Several methods were exploited in order to make the Ti coatings denser, including the incorporation of heavy, hard particles for in-situ peening during the coating deposition, and post deposition laser heating. Abstract only; no full-text paper available.