Abstract
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.
