Particle speed analysis in CoBlast

Abstract

The deposition of well-adhered thin type of coatings is of great importance in manufacturing and is used in numerous applications. Of particular interest in the biomedical sector is the deposition of hydroxyapatite onto titanium. CoBlast is a novel coating technology used mainly in the deposition of ceramics onto this metal. This is achieved by simultaneously blasting a ceramic particulate (the abrasive) and coating particles (the dopant) at a substrate with the resulting impregnation of the coating particles onto the substrate surface. The goal of this research was to investigate the velocities achieved by the abrasive particles under typical process pressures using a CoBlast nozzle. The velocity measurements were carried out using Particle Image Velocimetry by which method 200 μm aluminium oxide powder was investigated at pressures of 3, 4 and 5 bar at variable mass flow rates. Computational Fluid Dynamics using ANSYS-Fluent was used to predict the particle dynamics and results were compared to those obtained by the experiments. It was possible to generate valuable experimental data that provide an initial mean for process characterization and for the design of new and more efficient CoBlast nozzles.