Particle characterization and splat formation of plasma sprayed zirconia

A process map study has been carried out to examine the role of process variables on the properties of deposit formed in thermal spray. In the past, droplet size, temperature, and velocity have been widely used to interpret the status of in-flight particles. However, the limitation of those parameters on describing the molten fraction of refractory ceramics limits these parameters' qualifications and validation on examining the causes of the resulting deposit. In this study, a group parameter, melting index, is used to interpret the molten state of particles, which also reflects the thermal energy of the particles. The kinetic energy and fluidity of particles are characterized through their Reynolds number. Splat morphological features such as flattening and fragmentation are characterized against the group parameters. Deposition rate test confirms the significance of the concept of melting index. It is highlighted in this paper that particle group parameters, i.e., melting index and Reynolds number describe the particle in-flight status very well and can be used to predict the deposit behaviors.