Thermophysical properties of thermal sprayed coatings on carbon steel substrates by photothermal radiometry

Laser infrared photothermal radiometry (PTR) was used to measure the thermo physical properties (thermal diffusivity and conductivity) of various therm al sprayed coatings on carbon steel. A one-dimensional photothermal model o f a three-layered system in the backscattered mode was introduced and compa red with experimental measurements. The uppermost layer was used to represe nt a roughness-equivalent layer, a second layer represented the thermal spr ayed coating, and the third layer represented the substrate. The thermophys ical parameters of thermal sprayed coatings examined in this work were obta ined when a multiparameter-fit optimization algorithm was used with the bac kscattered PTR experimental results. The results also suggested a good meth od to determine the thickness of tungsten carbide and stainless-steel therm al spray coatings once the thermophysical properties are known. The ability of PTR to measure the thermophysical properties and the coating thickness has a strong potential as a method for in situ characterization of thermal spray coatings.