TitleNickel-Chromium Alloys: Engineered Microstructure via Spark Plasma Sintering
Publication TypeJournal Article
Year of Publication2014
AuthorsPasebani, S, Dutt, AK, Charit, I, Mishra, RS
JournalMaterials Science Forum
KeywordsAlloys, Annealing, Grain Boundaries, Hardness (Materials), Nickel (Metal), Powders (Particulate Matter), Sintering

There is a need to enhance or develop high temperature capabilities of structural materials for advanced coal‐fired power plants. These materials require a combination of high temperature strength, creep resistance and corrosion resistance in the oxygen‐rich and hydrogen‐rich high pressure environments. In this study, atomized Ni‐20Cr (wt.%) powder was mechanically milled with Y2O3 nanopowder (30‐40 nm powder size) to produce an alloy with a chemical composition of Ni‐20Cr‐1.2Y2O3 (wt.%) alloy using high energy ball milling. To minimize agglomeration during milling, 1 wt.% stearic acid was added to the powder mixture prior to milling. Microstructural characteristics of the powder were primarily characterized by the X‐ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystallite size and lattice strain were measured by XRD whereas powder morphology (powder size, shape) was studied by SEM. A milling time of 2 h was found to be optimal for the purpose that yttria particles are not dissolved yet uniformly distributed. Subsequently, the milled powder was consolidated into bulk specimens (12.5 mm in diameter) via spark plasma sintering (SPS) at 1100 °C for 30 minutes. Following SPS, the density and hardness of the specimens were measured. Microstructural characterization of the SPSed specimens was performed using SEM and TEM. The microstructural characteristics were correlated with the measured mechanical properties.