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18XV International Symposium on Self-Propagating High-Temperature Synthesis
SHOCK COMPACTION AND SINTERING OF Ni POWDERS: INFLUENCE OF Y2O3-C0O CONTAINING OXIDE FILMS
O. L. Pervukhina*" and A. S. Shishkina"
aMerzhnov Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, Chernogolovka, Moscow, 142432 Russia *e-mail: opervukhina@mail.ru
DOI: 10.24411/9999-0014A-2019-10122
In this work, we explored the influence of oxide nanofilms deposited onto the surface of Ni particles on the shock consolidation of Ni powders followed by their sintering. In our experiments, we used two Ni powders: the particles of one were covered with an Y2O3 film with a nominal thickness of 7 nm while those in the other, with an Y2O3-C0O film (Y/Co = 23/13 by wt) of the same thickness (7 nm).
Shock compaction in cylindrical geometry was carried out at two detonation velocities: 3000 and 4500 m/s. For the sake of comparison, the recovery ampoules were filled with pure, Y2O3-clad, and Y2O3-CoO-clad Ni powders in a layer-by-layer mode. Calculations of the loading parameters were carried out according to the method [1]. After shock compaction, the samples were extracted from the ampoule, cut into separate specimens, and then sintered at 875°C. The process of sintering was accompanied by some heat release in an identified reaction. The microstructure of compacts was characterized by optical microscopy, SEM, and XRD.
Shock compression did not destroy the deposited nanofilms but led to dense packing of powder particles accompanied by their deformation and surface activation, on retention of overall powder structure (Fig. 1). Note that shock compression also markedly decreased the sintering temperature (much below the melting point).
Fig. 1. Fragments of the compact Ni particles with deposited Y2O3-C0O film.
In compacts of pure Ni, we observed the presence of W and Mo in the particles bulk and the contact surface, as well as some amount of Fe (Fig. 2). Tentatively, this can be associated with sample overheating. In compacts of Y2O3-clad Ni particles, no new phases and steel components were detected. Hence the Y2O3 film prevents the diffusion of the elements into the particle bulk and facilitates strong bonding during shock compaction and subsequent sintering. For compacts of Y2O3-CoO-clad Ni particles, some interaction with a graphite base was noticed thus suggesting that in some surface areas the oxide film was absent.
Shock-consolidated Ni may find its use in some high-temperature applications requiring high corrosion/oxidation resistance.
iSHS 2019
Moscow, Russia
(a) (b)
Fig. 2. Microstructure of (a) compact pure Ni particles and (b) compact Ni particles with deposited Y2O3 film (b).
1. V.D. Rogozin, Vzryvnaya obrabotka poroshkovykh materialov, Volgograd: RPK Politekhnik, 2002, 135 p.
