Abstract
In plasma spraying, the individual droplet behavior at impact is the fundamental element to understand the resulting coating microstructure. A new experimental set-up, developed in SPCTS laboratory (Limoges, F) with two fast shutter cameras (exposure time : 100 ns…1ms) allows visualisation at impact of a single particle plasma sprayed with a direct current (d.c) torch. A fast two color pyrometer enables to monitor particle temperature just prior to its impact, its flattening and its thermal history. Working in parallel with a free falling drop experiment, enables to obtain larger (about three orders of magnitude) time and dimension scale (realized in Advanced Joining Process Laboratory, Toyohashi, J). Each technique gives interesting and complementary results thanks to pyrometric signals and images. Results obtained with plasma sprayed particles allow studying the matter ejections generated on impact splashing .while both techniques allow following the flattening splashing. Calculation and comparison of quenching rates for millimetre sized drops on a stainless steel substrate give indications concerning the disk shaped splat formation.
