This paper presents a thickness measurement method that can be used during thermal spraying. The new method is based on photogrammetry and image reconstruction and is able to measure complex 3D shapes with continuous contours. Initial results demonstrate the nondestructive nature of the method as well as its accuracy, versatility, and speed.

Laser infrared photothermal radiometry (PTR) can be used to determine the thermophysical properties (thermal diffusivity and conductivity) and interfacial defects (i.e. disbonding) of various thermal sprayed coatings on carbon steel substrates. PTR experimental results are compared with a one-dimensional photothermal model that can take into account roughness affects and interfacial defects by considering a roughness equivalent-layer and an equivalent-thermal resistance, respectively. The foregoing thermophysical parameters of the thermal sprayed coatings are obtained when a multi-parameter optimization algorithm is used to fit the PTR experimental results. The potential of the PTR technique for in-situ monitoring of the coating process and the characterization of the thermal sprayed coatings will be discussed in this paper.

This paper presents some results of an inspection program to detect coating-substract defects using a Michelson type of shear interferometer. Debonding defects are detected by properly loading the surface of the specimen in such a way that the interference fringe pattern is modified, rendering the debond readily visible. Image processing techniques are applied to enhance the detection and better define the debonding geometry. Load conditions, leading to a better detection of debondings, are also discussed. The technique allows to obtain information over a large area of the tested part, with a resolution one hundred of the wavelength of the light being used.