NiAl intermetallic prepared with reactive sintering and subsequent powder-metallurgical plasma-sintering compaction

Abstract

This paper proposes a novel method for powder-metallurgy preparation of compact NiAl intermetallics. In the first step, the NiAl powder is prepared with the reactive-sintering procedure. The porous NiAl product of the SHS reaction is milled to a fine powder and consequently compacted by SPS processing. The compaction of powder metals and alloys is a very difficult field due to the need of preserving the unique properties of the initial materials. One of the few possible methods of a successful compaction is plasma sintering. To describe detailed structures of powder-metallurgy materials, it is necessary to use advanced microscopy methods such as SEM and TEM. In this study, the structure of a NiAl intermetallic compound is described. The material was first produced, with reactive sintering, from pure elements. Subsequently, the NiAl porous master alloy was milled and compacted with the spark-plasma-sintering (SPS) technique. The particle size of the NiAl powder was comparable to the grain size of the compacted material, which exhibited a low porosity. It was proved that the interconnection of the NiAl particles is made by a thin layer of nanocrystalline oxides.