Application of vacuum plasma techniques for preparation of Ni-Cr-Dy powders proposed as masteralloys for combustion synthesis of Ni-Al intermetallics

Abstract

A promising approach to improve the high-temperature properties of Ni-Al intermetallics is macroalloying with chromium and microalloying with a small amount of rare-earth elements (REE). For powder manufacturing processes such as the combustion synthesis technique, macro- and microalloying can be achieved by employing Cr & REE containing masteralloy powders as one of the starting reagents along with nickel and aluminum powders. This study investigated a process of dysprosium deposition onto the particles of commercial Ni-Cr powder aimed to produce the Ni-Cr-Dy masteralloy powder. The process involves pretreatment of the particle surface by low-energy high-current electron beam (LEHCEB) and uniform magnetron deposition of a thin dysprosium film. The possibility of embedding the dysprosium film into the particle's surface using an additional stage of LEHCEB treatment has been considered. It has been observed that during LEHCEB modification, a change in the particle size distribution, smoothing of the surface, and the formation of an intermetallic Dy₃Ni phase in the subsurface layer occurs. A fraction of the obtained Ni-Cr-Dy powders were added to the starting powder blend for the combustion synthesis of Ni-Al-Cr-Dy porous alloys. It has been demonstrated that dysprosium uniformly distributes throughout the intermetallic scaffold of porous alloys and is localized within the Ni₃Al phase in the form of enriched regions and separate inclusions.