Effect of substrate preparation on flattening of plasma sprayed aluminium bronze powders

International audiencePlasma spray coatings are produced by introducing powder particles of the material into a plasma plume, which melts and forwards them to the substrate. The flattening process of these individual molten droplets is one of the most critical factors as the coating quality strongly depends on the deposition of individual particles. Powders of aluminium bronze, a fine (−53 + 11 μ m) and a coarse one (−125 + 45 μm) were plasma sprayed onto stainless steel substrates (AISI 304L) under atmospheric condition with three different substrate temperatures (25, 165 and 270°C). Two different ranges of surface roughness Ra were used: mirror polished substrates with about 0·01-0·03 μm and grit blasted substrates with about 1·89-2·43 μm. A scanning electron microscopy equipped with energy dispersive spectrometry system and an electron probe microanalysis, were used in order to study the splat morphology and the chemical composition of the splats

Effect of substrate roughness and temperature on splat formation in plasma sprayed aluminium bronze

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Effect of substrate temperature and roughness on the solidification of copper plasma sprayed droplets

International audienceFlattening of an individual thermal sprayed particle on the substrate is a fundamental process for the coating formation. Coating properties such as porosity and adhesion depend strongly from the splats morphology. Also, the microstructure of the coating depends on the nucleation and the grain growth during splats solidification. The influence of the substrate temperature and roughness on the microstructure of copper splats was examined in the present study. Copper (−90 + 45 μm) was plasma sprayed under atmospheric conditions on mirror polished (Ra not, vert, similar 0.02 μm) and on grit-blasted (Ra not, vert, similar 1.33 μm) stainless steel substrates (AISI 304L). The substrates were preheated at three different temperatures: 200 °C, 250 °C and 300 °C. A Schottky field emission scanning electron microscope (SFE-SEM) was used in order to study the splats microstructure. In order to measure the grain size of the splats, image analysis software was used, while the chemical composition of the splats was studied by an electron probe microanalysis (EPMA). It was found that the splats cooling velocity is decreased with the increase of substrate temperature above the transition temperature. Also a further decrease of splats cooling velocity was provoked by increasing the mean substrate roughness