Nanocomposites and nanomaterials

Features of spheroidization process of powders and structure formation of the coatings within plasma-arc sputtering of powder wires with additives of nanoscale refractory additives
Korzhyk V.M., Strohonov D.V., Demianov O.I., Shcheretskyi V.O., Avdeeva L.I., Tunik A. Ju. 
E.O. Paton Electric Welding Institute the NAS of Ukraine, 1 Kazymyr Malevych St., Kyiv 03150 Ukraine.

The regularities of the granulometric composition formation of spherical powders obtained by plasma-arc sputtering of flux-cored wires, a tubular steel shell type with fillers based on carbides WC, Cr3C2, B4C with nanoadditives NbC and ZrO2, with particle size up to 120 nm, in amount 5 wt.%. Particles size distribution of powder wire spraying products with WC filler were studied. It is stated that addition of nanoscale powders of NbC and ZrO2 promotes the average size reduction of the sprayed particles by 2.1 ... 2.5 times. At the same time, the number of the fine fractions (0,14+0.1; 0,1+0,045; 0,045+0 µm) increases significantly.
It was stated that addition of the nanoscale ZrO2 particles to the filler of a flux-cored wire with the filler based on boron carbide reduces average size of the sprayed particles, compared to the spraying of these powder fractions without nanoadditives, decrease is in 1.1 ... 1.2 times, while the amount of the fraction -0,14+0.1 μm increases almost in 1.5 times and fraction -0,045+0 µm in 1.8 times.
It was discovered that the addition of NbC nanopowder in process of plasma-arc spraying of coatings from flux-cored wires with WC fillers, inhibits the decarbidization process of tungsten carbides, and leads to an increase of the coatings` hardness up to 700 MPa. Addition of 0.5% of ZrO2 nanopowder to flux-cored wires with fillers: B4C, B4C + (Cr, Fe)7C3, B4C + (Cr, Fe) 7C3 + Al promotes refinement of the coatings` structure and to the formation of participates of dispersed borides Fe2B, Fe3B.