In-situ particle temperature, velocity and size measurements in the spray forming process

The structure and material properties of spray formed products depend directly on the thermal state of particles before they impact the substrate or on the already deposited layer. Monitoring particle temperature, velocity and size can thus provide a unique tool for optimizing the material properties as well as controlling spraying conditions during deposition. In this paper, an optical sensing device based on the principle of high-speed pyrometry, developed for on-line monitoring of particle temperature, velocity and diameter of in-flight particles during thermal spraying conditions (e.g. plasma guns), is for the first time applied and examined in the spray forming process. Thermal radiation emitted by the particles is collected by a sensing head attached to the spray cone and transmitted through optical fibers to a detection cabinet located away from the dusty environment. Tests were carried out with different materials, spray pressures and measurement positions to exhibit the efficiency of the measurement system in the spray forming process.