A Novel Approach to Determine In-Flight Particle Oxidation for Thermal Spraying Processes

• Published in: Journal of thermal spray technology 2020-06, Vol.29 (5), p.932-946
• Main Authors: Szulc, M., Kirner, S., Forster, G., Schein, J.
• Format: Article
• Language: English
• Subjects: Analytical Chemistry; Characterization and Evaluation of Materials; Chemistry and Materials Science; Corrosion and Coatings; Machines; Manufacturing; Materials Science; Peer Reviewed; Processes; Surfaces and Interfaces; Thin Films; Tribology
• ISSN: 1059-9630; 1544-1016
• DOI: 10.1007/s11666-020-01055-0

A careful substrate preparation and the physical properties of the coating particles are decisive for the quality and envisaged properties of the deposited layer. Temperature, size, rate and velocity represent the classical quantities, which can be measured in situ using various diagnostics. Nonetheless, another quality-determining parameter is the degree of oxidation which could not be measured in situ (up to now) by established diagnostics and must therefore be qualitatively derived from the above-mentioned quantities or subsequently be measured by means of destructive methods. Within this work, a diagnostic approach to determine in-flight particle oxidation has been outlined and tested. The presented measurement method detects the entire particle plume from different directions using a 2D two-color pyrometry and allows for the calculation of spatially resolved 3D temperature and intensity distributions based on a tomographic evaluation method. By additionally using measurements of the particle velocities and particle sizes, the surface emissivity of the particles along the spraying direction can be calculated, which in turn allows quantitative conclusions on the degree of particle oxidation. Investigations on the wire arc spraying process have shown that particle oxidation degrees could be determined and tend to correlate well with oxide contents in finished coatings.