The Characterization of a Gas-Atomized Ferritic Steel Powder Pre-alloyed with 6 Wt Pct Aluminum

In this paper, the microstructure of a gas-atomized steel powder pre-alloyed with aluminum (11.4 Cr, 10.0 Co, 5.7 Al, 5.1 Ni and Fe in wt pct) is characterized. The as-atomized powder contains NiAl-rich precipitates and most of the particles are covered with a thin (< 10 nm) Fe-rich oxide layer alloyed with aluminium. During the heating ramp of the sintering treatment, aluminum diffuses at the surface of the powder to grow an alumina layer which prevents sintering. When adding copper to the powder mix, however, liquid copper diffuses at the interface between steel and alumina, detaches alumina filaments from the steel and reshapes them into rounded particles. The evolution of the microstructure and the hardness are described as a function of tempering temperatures and time. Finally, the possibility of 3D printing this powder using the selective laser melting technique is investigated.