Abstract
An industrial and cost-effective online quality control method for thermally sprayed coatings will be presented. A new concept in pulse-thermography allows online, during the spraying process, the non-destructive evaluation of coated surfaces. This technique employs a heat source that produces a heat impulse. The impulse is directed toward the examined surface and the from the surface reflected and/or emitted signal is collected by an infrared-camera and subsequently treated in a computer. It will be demonstrated that the spraying process itself can be used as a heat source. In principle, the fading behavior of the signal captured by a high speed infrared camera is observed, or else the progression of the induced heat wave within the coating. Differences in coating thickness, coating and adhesion defects, microstructural changes, an aggregation of pores as well as oxide or metallic inclusions provoke a significant change in the signal intensity and are therefore detected. Pulse-thermography enables the non-destructive assessment of the quality of thermally sprayed coatings. A coated part can be examined to check if the desired coating structure has been successfully attained or if and where there are any areas with critical deviations in respect to coating thickness or coating microstructure. The simple set-up allows the integration of the technique in the production line.
