Layer structure formation induced by in-situ deposit surface temperature under different scanning methods during thermal spraying

Abstract

Plasma spraying-physical vapor deposition (PS-PVD) and atmospheric plasma spraying (APS), as new thermal spraying process, could prepare advanced thermal barrier coatings by successive scanning deposition layer by layer. To investigate the layer structure of the coating, the transient in-situ deposit surface temperature was investigated by varying the scanning methods. Results show that, compared to unidirectional scanning method, alternating scanning method results in doubling heating duration, higher in-situ deposit temperature rising and thereby thicker well-bonded layer structure during each spray cycle for the coating deposited at the edge position of the scanning path. The erosion resistance of the coatings deposited by unidirectional scanning method is independent on deposition positions including edge position and center position. However, the erosion resistance of the coatings deposited at edge position by alternating scanning method is one time higher than those deposited by unidirectional scanning method. Finally, the erosion mechanism of layer spallation is revealed to explain the difference between different scanning methods.