  Stainless steel particles (60 $\mu$m in mean diameter) cladded with an
alumina shell (2 $\mu$m thick and manufactured by mechanofusion) were sprayed
with an Ar-H2 (53-7 slm) d.c. plasma jet (I = 500 A, P = 28 kW, \rho_th = 56
%). Two main types of particles were collected in flight, as close as 50 mm
downstream of the nozzle exit: particles with a steel core with pieces of
alumina unevenly distributed at their surface and those consisting of a
spherical stainless steel particle with an alumina cap. The plasma flow was
modeled by a 2D steady parabolic model and a single particle trajectory by
using the 3D Boussinesq-Oseen-Basset equation. The heat transfer, within the
two-layer, stainless steel cladded by alumina, particle, considered the heat
propagation phenomena including phase changes. The models allowed determining
the positions, along the particle trajectory, where the convective movement
could occur as well as the entrainment of the liquid oxide to the leading edge
of the in-flight particles. The heat transfer calculations showed the
importance of the thermal contact resistance TCR between alumina and steel.
