Although detonation sprayed coatings are harder and better adhered than those achieved by plasma and even HVOF spraying, the method is far less used due to productivity and equipment challenges associated with mechanical valving and intermittent powder flows. This study shows how the use of propane as a fuel eliminates the need for mechanical valving and allows for continuous powder feeding through a high-frequency detonation spray gun. To demonstrate the capabilities of valveless detonation spraying, WC-CoCr powders were deposited under different conditions (oxygen-to-fuel ratio, flow rate, shot frequency) and the resulting coatings were assessed based on porosity, microhardness, deposition efficiency, and phase composition.

In order to address deficiencies in thermal spray coatings applied using air plasma spraying (APS) and high velocity oxygen fuel (HVOF), namely, adhesion, cohesion, porosity and line of sight limitations, novel hybrid coatings using post - thermal spray chemical vapor deposition via the pack cementation process were developed. Coatings based on tungsten carbide-cobalt chrome and chrome carbide-nickel chrome followed by boron or chrome diffusion were applied to multistage and single stage pump components for severe service applications in sand and alumina catalyst. Field testing established the effectiveness of using the dual coating approach.

To overcome the problem of depositing dense refractory coatings, a study was undertaken on the effect of using three plasma gases simultaneously when depositing tungsten and tungsten alloys utilizing Low Pressure Plasma Spraying (LPPS). A greater degree of control of the plasma flame temperature, jet velocity, and heat transfer capability is believed to occur when using ternary gas mixtures. Samples were prepared and coated using Argon, Helium, and Hydrogen in different ratios. Variations of chamber pressures were used as an additional parameter to control and optimize the deposits. The samples were sectioned and analyzed. Microstructural features such as porosity, unmelted particles, and grain size, were characterized using optical and Scanning Electron Microscopy (SEM). Fractography was used to determine lamellar thickness and distribution. Mechanical properties were evaluated by measuring the microhardness of the different coatings in comparison to one another.