Can the addition of rhenium enhance the fracture toughness of NiAl ?

Significance 

Recently, aerospace technology has undergone rapid development to meet new demands in the sector such as increasing the engine operating temperature. Therefore, researchers have been looking for new materials suitable for such functions and have identified nickel aluminide as a promising solution owing to its excellent properties including low density, high melting point and good thermal conductivity. Unfortunately, nickel aluminide exhibits poor ductility and low fracture toughness at room temperature. This makes it inappropriate to use nickel aluminide material for heavy structural applications.

Generally, several methods are available for nickel aluminide production. For instance, powder metallurgy techniques are used to reduce the problems associated with intermetallic machining. Thus, it can effectively be used for alloying of nickel aluminide with the addition of ternary components such as rhenium. In a recently published literature, rhenium results in significant mechanical properties improvement by dissolving fully in e.g. a chromium matrix of chromium-alumina composite obtained by pressure sintering. This is a key consideration in subsequent research works when using the powder metallurgy technique to manufacture such materials.

Researchers at Polish Academy of Sciences Mr. Kamil Bochenek, Dr. Witold Węglewski, Professor Jerzy Morgiel and Professor Michał Basista proposed the addition of rhenium to nickel aluminide to improve its mechanical properties without compromising the oxidation resistance. The authors utilized two powder metallurgy techniques including spark plasma sintering and hot pressing to obtain the sinters. The enhancement of the oxidation behavior and fracture toughness were investigated based on microscopic observations. Furthermore, a numerical model was developed to verify the hypothesis of the fracture toughness enhancement mechanism of the resulting material at different amounts of added rhenium. Their work is published in the research journal, Materials Science and Engineering.

From the experimental research, the authors observed that rhenium particles at the boundaries of nickel aluminide grains resulted in significant improvement of the fracture toughness and the flexural strength of the nickel aluminide by addition of only small amounts of rhenium. Moreover, very low mass changes were noted during oxidation at temperatures 900 °C, 1100 °C and 1300 °C due to the degradation of the protective aluminum oxide layer formed initially on the surface. Among the tested materials, eutectic composition sintered by hot pressing proved to be the best for enhancing fracture toughness, whereas beyond the eutectic concentration, a decrease was observed. Furthermore, finite element method simulations showed that the strengthening of nickel aluminide grain boundaries by rhenium was the main mechanism responsible for the enhanced fracture toughness.

The study by Polish Academy of Sciences scientists successfully used powder metallurgy method to enhance the fracture toughness of nickel aluminide by adding rhenium. Even though the solubilities of the rhenium were merely approximated based on earlier research works, the results can still be adopted and improved. Therefore, it will provide good replacements for nickel-based superalloys and thus advance the aerospace technology.

Can the addition of rhenium enhance the fracture toughness of NiAl ? - Advances in Engineering

About the author

Jerzy Morgiel received his Master Degree in Solid State Physics from the AGH Technical University in Kraków in 1981, and his PhD on shape memory alloys in Materials Science from the Institute for Metal Research of the Polish Academy of Sciences Kraków in 1987. Afterwards, he won Fulbright-Highs scholarship, what allowed him to investigate crystallization of silicon with in-situ HREM method at R. Sinclair group at Stanford University. Back in Poland he took over as a head of TEM Laboratory at the Institute of Metallurgy and Materials Science of Polish Academy of Sciences, where he received his D.Sc. (2002) and full professorship in (2012). Since 2015 he serves as President of the Polish Society for Microscopy.

His field of expertise concerns the study of phase transformation in solid state using electron microscopy methods.

About the author

Kamil Bochenek is a PhD student at the Department of Mechanics of Materials at the Institute of Fundamental Technological Research of Polish Academy of Sciences in Warsaw, Poland. He graduated from the AGH University of Science and Technology in Cracow in 2011 and holds MSc degree in Materials Engineering.

His current research is focused on intermetallic materials for high temperature aerospace application, which is the subject of his PhD thesis. His research interests also include metal-matrix composites manufacturing for automotive industry, novel composite materials and coatings for applications in energy industry.

About the author

Michał Basista is Associate Professor at the Institute of Fundamental Technological Research (IPPT) of Polish Academy of Sciences in Warsaw, where he is heading the Advanced Composite Materials Division. He holds a PhD and DSc degree in Mechanics obtained from IPPT. Besides IPPT he was conducting research on damage and fracture of materials during long term stays at Darmstadt University of Technology (Germany), University of Illinois at Chicago Circle (USA) and Arizona State University at Tempe (USA).

His current research interests combine processing, characterization and modeling of metal-ceramic composites. Specific areas of his expertise include composites manufacturing by powder metallurgy, experiments and modeling of mechanical properties, measurement and numerical simulations of residual stresses, modeling and testing of composites at the microscale.

About the author

Dr. Witold Węglewski is Assistant Professor at the Institute of Fundamental Technological Research (IPPT) of Polish Academy of Sciences in Warsaw. He received his Master’s degree in Mechanical Engineering from the Warsaw University of Technology, Faculty of Automotive and Construction Machinery Engineering in 2002 and PhD degree in Mechanics in 2009 at IPPT.

His current research activities comprise processing of metal-matrix composites by powder metallurgy, experimental measurements and numerical modeling of thermal residual stress and mechanical properties of composites, theoretical and numerical modeling of composites fracture.

Reference

Bochenek, K., Węglewski, W., Morgiel, J., & Basista, M. (2018). Influence of rhenium addition on microstructure, mechanical properties and oxidation resistance of NiAl obtained by powder metallurgy. Materials Science and Engineering: A, 735, 121-130.

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