Explosive consolidation of 316L stainless steel powder - Effect of phase composition

Two stainless steel (SS) AISI 316L powders have been processed by explosive consolidation using a cylindrical configuration. Powders with d(50) of 9 and 5 mu sm and a phasic structure consisting of fcc and bcc are used. After shock processing (3.5 up to 4.9 mm/mu s) hardness was evaluated. Powders with the lowest particle size and processed with the highest detonation velocities (4.9 and 4.1 mm/mu s) gave rise to a bulk material where in the centre occurred a phase transformation of bcc to fcc phase. Nevertheless, the hardness values were dissimilar along the cross section depending on the macrodefects (centre hole and cracks) produced by detonation. After a pre-heating treatment (900 degrees C), this powder was full austenitic (fcc) and when submitted to explosive consolidation, it led a monolithic solid without cracks, with a density of 99% TMD (theoretical maximum density) and a hardness of 3.1 GPa. This value is lower than others measured, particularly when a centre hole is not present, revealing hardening by plastic deformation. Concerning powder with higher particle size (d(50) = 9 mu m), the presence of mainly austenite induces after shock processing function of detonation parameters and localisation hardness values from 3.9 up to 5.0 GPa. The homogeneity of hardness reflex of absence of defects and low stress are almost achieved only for low particle size powders, using the lowest detonation velocities (3.4 GPa). (C) 2014 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.