Plasmotron for coatings application from fuel-dispersed materials

One of the most productive, technological and effective methods of obtaining protective coatings on aerospace de- vices from the impact of significant dynamic loads, corrosive media, high temperatures, neutron fluxes, and the like is plasma spraying. The main element that provides the necessary characteristics for the particles to be sprayed is a plasma torch. The world has developed a large number of plasma torches of various designs, each of them has its own advantages and disadvantages. In general, the sputtered material is fed into the plasma jet radially through the channel located on the nozzle cut, which adversely affects the quality of the coating and the utilization of the material, since uneven heating of the sputtered refractory dispersed materials (oxides, carbides, nitrides, etc.) occurs. To ensure heat- ing of the sprayed material, the power of the plasma torch is increased, which reduces the service life of the plasma torch. There is a scheme for supplying a transport gas with a powder in a plasma flow, allowing more efficient and uni- form heating of the deposited material, and also providing for additional stabilization of the arc discharge, but on an industrial scale such plasmatrons are not produced, since they are technologically difficult to produce. A plasma torch was developed and manufactured in this way. Comparative experimental studies on the deposition of refractory materi- als by the imported plasma torch F4 (Switzerland) and the developed PM-1 have been carried out. For the comparative analysis of plasmatrons, the material of the samples was chosen as steel 45, a material for deposition of the oxide Al2O3, which is used mainly as a heat-shielding coating. Sputtering Al2O3 on steel was produced through a cermet sublayer (40 % Al2O3 + 60 % NiCr by volume) to smooth the coefficients of thermal expansion. It was found that the coatings applied by the modernized plasmatron PM-1 have a higher bond strength and a greater thickness (about 20 %), and porosity is lower by 13 % than that of plasmatron-coated coatings F4 (Switzerland).