Investigation of plasma sprayed coatings formation by visualization of droplet impact and splashing on a smooth substrate

In plasma spraying, individual droplet behavior at impact with the substrate is the fundamental element in understanding of coating microstructure. A new experimental setup with two fast shutter cameras (exposure time: 100 ns...1 ms) provides visualization at impact of a single particle, plasma sprayed with a direct current (dc) torch. Images of plasma-sprayed particles at impact on a smooth substrate are presented. The resultant splashing phenomena can be resolved into two parts: the initial impact and particle flattening response. Matter ejection due to the impact is independent of the substrate temperature but this is not the case for flattening splashing. Image correlation with recorded test parameters signals, transistor-transistor logic (TTL) pulse for cameras triggering, pyrometer signal, enable the events chronology, which is essential for the understanding the complete phenomena, to be studied.