Oxidation behaviour of a novel refractory high entropy alloy at elevated temperatures
Introduction
Research on the new materials for high temperature application with capabilities beyond Ni-based superalloy has drawn great attention. Following the recently developed concept of high entropy alloy [1], Senkov et al. [2] proposed RHEA as a potential material for high temperature applications. By combining multiple refractory elements in similar atomic fractions, the RHEA exhibits attractive mechanical properties at 1200 °C and above [3,4], which is beyond the temperature limitations of Ni-based superalloys [5]. But for high temperature applications in the atmosphere, oxidation is an important issue. To the best of authors’ knowledge, there were very limited reports on the oxidation mechanisms and associated microstructure characterization for RHEAs to date [[6], [7], [8], [9], [10], [11], [12], [13], [14]], especially for temperatures at 1200 °C and above. Currently, the oxidation resistance of RHEA is still inadequate for high temperature applications since there is no RHEA that can spontaneously form protective oxide layers, such as Al2O3, SiO2, and Cr2O3, at high temperatures. In our previous work [14], a novel RHEA “NV1” was presented to possess parabolic mass gain behaviours at 1100 °C during oxidation; this article presents the oxidation behaviours of NV1 at 1200, 1300, and 1400 °C up to 100 h. The study on such unprecedent temperature range and testing duration would shed more light on understanding the oxidation mechanisms of RHEA.
Section snippets
Material and methods
The ingot of NV1 was prepared by means of cold crucible levitation melting with nominal mixture of high purity (>99.9 wt%) elements and machined into specimens by electrical discharge machining. The composition of the as-cast ingot was determined with Shimadzu Lab Center XRF-1800. The as-cast microstructure of NV1 showed dendritic microstructure, with Mo-rich body centred cubic phase as dendrite arm, Cr-rich hexagonal Laves phase and minor Al-rich tetragonal phase as inderdendritic region. More
Results
The isothermal oxidation kinetics curves of NV1 alloy at 1200, 1300, and 1400 °C are shown in Fig. 1a. After 100 h of oxidation, the mass gain per initial surface area is 6.00, 9.91, and 18.43 mg/cm2 at 1200, 1300, and 1400 °C, respectively. A single mass gain dependence is observed within 100 h of oxidation at 1200 °C, which can be described by Equation (1):
Interestingly, three different trends of mass gain dependence are observed during the oxidation at 1300 °C, which can be
Discussion
NV1 alloy exhibits distinctly different oxidation behaviours at 1200, 1300, and 1400 °C, Fig. 1a. Since XRD patterns indicate the major component of the oxide near the top surface is rutile-type oxide for all specimens (Fig. 2), the microstructural evolution could play an important role in the different oxidation behaviours between and within different temperatures.
At 1200 °C, a complex OL bearing mainly rutile-type oxide with Al2O3 and Cr2O3 dispersion is formed, Fig. 3a. The rutile-type oxide
Conclusions
NV1 alloy exhibits distinctly different oxidation behaviours at 1200, 1300, and 1400 °C up to 100 h: a single parabolic behaviour was observed at 1200 °C owing to the formation of a complex rutile-type external OL with Al2O3 and Cr2O3 dispersion; the deterioration of the complex OL caused by Cr2O3 evaporation resulted a 3 stages oxidation at 1300 °C; both Cr2O3 evaporation and mullite formation led to a single power-law behaviour at 1400 °C. In addition, nitride particles are detected in all
CRediT authorship contribution statement
Kai-Chi Lo: Conceptualization, Methodology, Data curation, Writing - original draft, Visualization, Investigation, Writing - review & editing. Hideyuki Murakami: Supervision, Writing - review & editing. Jien-Wei Yeh: Supervision. An-Chou Yeh: Conceptualization, Methodology, Supervision, Writing - review & editing.
Acknowledgements
This study was a collaboration between National Tsing Hua University, Taiwan and National Institute for Materials Science (NIMS), Japan. This work is supported by NIMS under the International Cooperative Graduate Program; Ministry of Science and Technology (MOST) in Taiwan under Grant MOST106-2923-E-007-002-MY2, MOST107-2218-E-007-012, and MOST107-3017-F-007-003; and the “High Entropy Materials Center” from The Featured Areas Research Center Program within the framework of the Higher Education
References (28)
- et al.
Refractory high-entropy alloys
Intermetallics
(2010) - et al.
Mechanical properties of Nb25Mo25Ta25W25 and V20Nb20Mo20Ta20W20 refractory high entropy alloys
Intermetallics
(2011) - et al.
Microstructure and oxidation behavior of new refractory high entropy alloys
J. Alloy. Comp.
(2014) - et al.
Phase equilibria, microstructure, and high temperature oxidation resistance of novel refractory high-entropy alloys
J. Alloy. Comp.
(2015) - et al.
High temperature oxidation behavior of an equimolar refractory metal-based alloy 20Nb20Mo20Cr20Ti20Al with and without Si addition
J. Alloy. Comp.
(2016) - et al.
Accelerated oxidation in ductile refractory high-entropy alloys
Intermetallics
(2018) - et al.
Aluminizing for enhanced oxidation resistance of ductile refractory high-entropy alloys
Intermetallics
(2018) - et al.
The influence of CrTaO4 layer on the oxidation behavior of a directionally-solidified nickel-based superalloy at 850–900 °C
J. Alloy. Comp.
(2017) - et al.
The role of aluminum additions in the oxidation and wear of a TaC:C low-friction coating
Surf. Coat. Technol.
(2009) - et al.
Laser shock processing effects on isothermal oxidation resistance of GH586 superalloy
Appl. Surf. Sci.
(2015)
Structure and properties of mullite—a review
J. Eur. Ceram. Soc.
Glass formation and characterization in the 3Al2O3· 2SiO2-LaPO4 system
J. Non-Cryst. Solids
Nanostructured high‐entropy alloys with multiple principal elements: novel alloy design concepts and outcomes
Adv. Eng. Mater.
Microstructure and properties of aluminum-containing refractory high-entropy alloys
JOM (J. Occup. Med.)
Cited by (40)
In situ formation of micro arc oxidation ceramic coating on refractory high entropy alloy
2024, International Journal of Refractory Metals and Hard MaterialsOxidation behavior and microstructural evolution of FeCoNiTiCu five-element high-entropy alloy nanoparticles
2024, Journal of Materials Science and TechnologyCooperative regulation of mechanical properties and magnetoresistance effect in high-entropy alloys by spinodal decomposition
2024, Journal of Alloys and CompoundsRefractory high-entropy alloys: A focused review of preparation methods and properties
2023, Journal of Materials Science and TechnologyMicrostructure and oxidation behavior of Co–Cr–Ta ternary alloys
2023, Journal of Alloys and Compounds