Direct current plasma spraying of mechanofused alumina-steel particles

TL;DR

This study investigates the behavior of alumina-steel composite particles during direct current plasma spraying, modeling heat transfer and particle trajectories to understand coating formation and the effects of thermal contact resistance.

Contribution

It introduces a combined experimental and modeling approach to analyze alumina-steel particle behavior in plasma spraying, emphasizing the role of thermal contact resistance.

Findings

Particles with uneven alumina distribution and alumina caps were collected.

Heat transfer modeling highlighted the significance of thermal contact resistance.

Particle trajectories and phase changes were characterized during spraying.

Abstract

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.