A Universal Method for Representation of In-Flight Particle Characteristics in Thermal Spray Processes

Abstract

The advent of user-friendly in-flight process diagnostic tools has significantly improved our understanding of thermal spray processes. This paper examines the critical attributes of these diagnostic measurements and the applicability of the nondimensional group parameters as a mapping strategy for data visualization. Specifically, first-order process maps (process-particle interactions) have been addressed by converting the temperature (T)-velocity (V) of particles obtained via diagnostics into nondimensional group parameters [Melting Index (MI)-Reynolds number (Re)]. This approach provides an improved description of the thermal and kinetic energy of particles and allows for cross comparison of diagnostic data within a given process for different materials, comparison of a single material across different thermal spray processes, and detailed assessment of the melting behavior through recourse to analysis of the distributions. An additional group parameter, Oxidation Index (OI), has been applied to relatively track the oxidation extent of metallic particles under different operating conditions.

Optimization and Characterization of High Velocity Oxy-fuel Sprayed Coatings: Techniques, Materials, and Applications

“…In tandem with the diagnostic tool development, a novel comprehensive optimization tool has been developed for thermal spray processes. The process mapping concept was first introduced by Professor Sanjay Sampath [6], and its use has increased since introduction [7][8][9][10]. In this chapter the diagnostic equipments are introduced, as well as the process mapping tool and factors related to it.…”

“…These diagnostic tools are nowadays robust, user-friendly and cost-effective, and therefore their use has increased strongly. Principle objectives of diagnostic tools are to measure the variables of particles within the spray stream, i.e., velocity, temperature, flux, trajectory, and size distribution, which all have influence on the microstructure and properties of sprayed coatings [9]. The sensors are mainly based on two-wavelength pyrometry and time triggered measurement of velocity.…”

“…Especially with ceramic materials, with low thermal conductivity, the particle surface temperature does not directly indicate the particle melting status due to large temperature gradient within the particle [9,18]. The particle surface may even evaporate before the core melts.…”

Structurally Integrated, Damage-Tolerant, Thermal Spray Coatings

“…The use of these sensors also enables establishing first-order process maps for TS, where the direct effect of feedstock material, torch hardware, and operating conditions on the spray stream can be visualized. With this knowledge, expanded temperature and velocity maps (e.g., quantified based on melting state and kinetic energy) can be constructed across multiple materials and processes 13,14 and serve as a guide for tuning process parameters to optimize the desired characteristics of a depositing particle, such as adequate temperature for the melting of the particle or maximizing the velocity for peening intensity and coating compaction.…”

Particle in-flight behavior and its determining the microstructure and mechanical properties of zirconia based thermal barrier coatings

“…Although many reports which associated with the effect of microstructure on the properties of as-sprayed coatings can be found [12][13][14][15], the detailed information on the relationship between particle in-flight behavior, defect and mechanical properties of YSZ coatings is still scarce. In view of the above, the correlation between particle in-flight behavior and coating defects was established and the influence of defects on the mechanical properties of assprayed coatings was further studied.…”