Densification and microstructure changes of micron size nickel powder during direct induction sintering

Abstract

Induction heating is an attractive technique to sinter metal powders in a short time and with limited energy. A series of direct induction sintering experiments has been performed with a micron size nickel powder in a dedicated set-up with 50 or 150 kHz current frequency and several heating rates, up to 900°C min⁻¹. With a view to better catching the specific outcome of induction sintering, conventional sintering tests have also been achieved and their results in terms of densification have been depicted by adjusting a Master Sintering Curve model. The main conclusion of this study is that nickel specimens with high density, reasonably low grain size and homogeneous microstructure can be obtained by direct induction sintering with processing times much smaller than typical conventional sintering times. The obtained data also show that powder densification is accelerated during induction sintering, which is supposedly due to the enhancement of diffusion under electric current.