Abstract
Suspension Plasma Spraying is one of the newest thermal spray processes. It uses liquid feedstock instead of dry powders, as it is in case of conventional Powder Plasma Spraying. The suspension preparation process should be optimized individually depending on the powder material to avoid poor suspension stabilization, fast sedimentation of solids or too high viscosity. However, regardless of the liquid feedstock preparation, each kind of suspension causes some technological problems during spraying. In this study the possibility of using high power ultrasonic waves to support the suspension feeding and injection was investigated. The idea was to break the powder agglomerates before the suspension goes through the injector (in the pipeline system). The in-line ultrasonic dispersion system was designed. The geometry of all important components (transducer, booster and horn) was analyzed and calculated depending on the frequency and power of ultrasounds. By using modal analysis and Finite Element Method (FEM) the propagation of ultrasonic wave was simulated for different sonotrode geometries, called: (i) stepped, (ii) exponential, (iii) catenoidal and (iv) tapered. The in-house system was initially tested in order to see if all elements were designed and manufactured properly. Finally, the ultrasonic cavitation was observed inside the feeding pipeline system, which should allow dispersing the suspension prior to its injection into the plasma jet.
