Low-Density, High-Temperature Co Base Superalloys

2021 ◽  
Vol 51 (1) ◽  
Author(s):  
Surendra Kumar Makineni ◽  
Mahander Pratap Singh ◽  
Kamanio Chattopadhyay
Keyword(s):  
High Temperature ◽  
Elevated Temperatures ◽  
Ternary Alloys ◽  
Specific Yield ◽  
Annual Review ◽  
Publication Date ◽  
High Temperature Strength ◽  
Low Density ◽  
Face Centered Cubic ◽  
Alloy Development

Co base superalloys strengthened by coherent L12 ordered γ′ precipitate in a disordered face-centered cubic γ matrix represent a new opportunity for high-temperature alloy development. The emergence of alloys with low density and high specific yield strength at elevated temperatures has further energized the research and development efforts in the last 5 years. Initially stabilized by the addition of small amounts of Nb and Ta, these new generations of alloys with multiple alloying additions to form basic quaternary and ternary alloys have steadily expanded the property envelopes to raise hope for a modern class of superalloys with higher-temperature capabilities. This article reviews the work of a vibrant set of researchers across the globe whose findings are constantly unlocking the potential of these alloys. These developments have achieved high-temperature strength (at 870°C) >0.6 GPa, γ′ solvus temperature exceeding 1,100°C, and densities between 7.8 and 8.6 g/cm3. Expected final online publication date for the Annual Review of Materials Science, Volume 51 is August 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Phase transformation and layer evolution in molybdenum disilicide-silicon carbide nanolayered coatings

1994 ◽  
Vol 52 ◽  
pp. 538-539
Author(s):  
H. Kung ◽  
T. R. Jervis ◽  
J.-P. Hirvonen ◽  
M. Nastasi ◽  
T. E. Mitchell ◽  
...  
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Oxidation Resistance ◽  
Elevated Temperatures ◽  
Matrix Material ◽  
Molybdenum Disilicide ◽  
High Temperature Strength ◽  
Cross Sectional ◽  
Good Oxidation Resistance ◽  
Structural Applications

MoSi2 is a potential matrix material for high temperature structural composites due to its high melting temperature and good oxidation resistance at elevated temperatures. The two major drawbacksfor structural applications are inadequate high temperature strength and poor low temperature ductility. The search for appropriate composite additions has been the focus of extensive investigations in recent years. The addition of SiC in a nanolayered configuration was shown to exhibit superior oxidation resistance and significant hardness increase through annealing at 500°C. One potential application of MoSi2- SiC multilayers is for high temperature coatings, where structural stability ofthe layering is of major concern. In this study, we have systematically investigated both the evolution of phases and the stability of layers by varying the heat treating conditions.Alternating layers of MoSi2 and SiC were synthesized by DC-magnetron and rf-diode sputtering respectively. Cross-sectional transmission electron microscopy (XTEM) was used to examine three distinct reactions in the specimens when exposed to different annealing conditions: crystallization and phase transformation of MoSi2, crystallization of SiC, and spheroidization of the layer structures.

High-Entropy Ultra-High-Temperature Borides and Carbides: A New Class of Materials for Extreme Environments

2021 ◽  
Vol 51 (1) ◽  
Author(s):  
Lun Feng ◽  
William G. Fahrenholtz ◽  
Donald W. Brenner
Keyword(s):  
High Temperature ◽  
Extreme Environments ◽  
Experimental Studies ◽  
Heat Fluxes ◽  
Annual Review ◽  
Publication Date ◽  
Structure Property ◽  
High Entropy ◽  
Ultra High Temperature Ceramics ◽  
Ultra High Temperature

Herein, we critically evaluate computational and experimental studies in the emerging field of high-entropy ultra-high-temperature ceramics. High-entropy ultra-high-temperature ceramics are candidates for use in extreme environments that include temperatures over 2,000°C, heat fluxes of hundreds of watts per square centimeter, or irradiation from neutrons with energies of several megaelectron volts. Computational studies have been used to predict the ability to synthesize stable high-entropy materials as well as the resulting properties but face challenges such asthe number and complexity of unique bonding environments that are possible for these compositionally complex compounds. Experimental studies have synthesized and densified a large number of different high-entropy borides and carbides, but no systematic studies of composition-structure-property relationships have been completed. Overall, this emerging field presents a number of exciting research challenges and numerous opportunities for future studies. Expected final online publication date for the Annual Review of Materials Science, Volume 51 is July 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Emerging Capabilities for the High-Throughput Characterization of Structural Materials

2021 ◽  
Vol 51 (1) ◽  
Author(s):  
Daniel B. Miracle ◽  
Mu Li ◽  
Zhaohan Zhang ◽  
Rohan Mishra ◽  
Katharine M. Flores
Keyword(s):  
High Throughput ◽  
Materials Science ◽  
Structural Materials ◽  
Rapid Screening ◽  
Annual Review ◽  
Publication Date ◽  
Synthesis Methods ◽  
Alloy Development ◽  
Composition Gradients ◽  
Future Vision

Structural materials have lagged behind other classes in the use of combinatorial and high-throughput (CHT) methods for rapid screening and alloy development. The dual complexities of composition and microstructure are responsible for this, along with the need to produce bulk-like, defect-free materials libraries. This review evaluates recent progress in CHT evaluations for structural materials. High-throughput computations can augment or replace experiments and accelerate data analysis. New synthesis methods, including additive manufacturing, can rapidly produce composition gradients or arrays of discrete alloys-on-demand in bulk form, and new experimental methods have been validated for nearly all essential structural materials properties. The remaining gaps are CHT measurement of bulk tensile strength, ductility, and melting temperature and production of microstructural libraries. A search strategy designed for structural materials gains efficiency by performing two layers of evaluations before addressing microstructure, and this review closes with a future vision of the autonomous, closed-loop CHT exploration of structural materials. Expected final online publication date for the Annual Review of Materials Science, Volume 51 is August 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Mechanical Properties and Microstructure of the Newly Developed Steel (Low C 18Cr-11Ni-3Cu-Mo-Nb-B-N) After Aging Treatment

2020 ◽  
Author(s):  
Nao Otaki ◽  
Tomoaki Hamaguchi ◽  
Takahiro Osuki ◽  
Yuhei Suzuki ◽  
Masaki Ueyama ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Vickers Hardness ◽  
Elevated Temperatures ◽  
Rupture Strength ◽  
Aging Treatment ◽  
High Strength ◽  
High Temperature Strength ◽  
Short Term ◽  
Rich Phase

Abstract In petroleum refinery plants, materials with high sensitization resistance are required. 347AP has particularly been developed for such applications and shows good sensitization resistance owing to its low C content. However, further improvement in high temperature strength is required for high temperature operations in complex refineries, such as delayed cokers. Recently, a new austenitic stainless steel (low C 18Cr-11Ni-3Cu-Mo-Nb-B-N, UNS No. S34752) with high sensitization resistance and high strength at elevated temperatures has been developed. In this study, the mechanical properties and microstructures of several aged specimens will be reported. By conducting several aging heat treatments in the range of 550–750 °C for 300–10,000 h on the developed steel, it was revealed that there were only few coarse precipitates that assumed sigma phase even after aging at 750 °C for 10,000 h. This indicates that the newly developed steel has superior phase stability. The developed steel drastically increased its Vickers hardness by short-term aging treatments. Through transmission electron microscopy observations, the fine precipitates of Cu-rich phase were observed dispersedly in the ruptured specimen. Therefore, the increase in Vickers hardness in short-term aging is possibly owing to the dispersed precipitation of Cu-rich phase. There was further increase in Vickers hardness owing to Z phase precipitation; however, the increment was smaller than that caused by Cu-rich phase. The newly developed alloy demonstrated excellent creep rupture strength even in the long-term tests of approximately 30,000 h, which is attributed to these precipitates.

The Effect of Ni on the High-Temperature Strength of Al-Si Cast Alloys

2011 ◽  
Vol 690 ◽  
pp. 274-277 ◽  
Author(s):  
Florian Stadler ◽  
Helmut Antrekowitsch ◽  
Werner Fragner ◽  
Helmut Kaufmann ◽  
Peter J. Uggowitzer
Keyword(s):  
High Temperature ◽  
Load Transfer ◽  
Elevated Temperatures ◽  
Close Contact ◽  
Sem Analysis ◽  
High Temperature Strength ◽  
Phase System ◽  
Two Phase ◽  
Eutectic Si ◽  
Cast Alloys

In order to investigate the effect of Ni on the high-temperature strength of Al-Si cast alloys, tensile properties of hypoeutectic and eutectic alloys were determined at 250 °C after long-term annealing at test temperature. LOM- and SEM-analysis revealed the existence of Al3Ni-phases in close contact to eutectic Si. It was shown that the strength can be increased by the addition of Ni, though just to a certain level, depending on the fraction of eutectic phase in the alloy. The alloys were considered as a coarse two-phase system where a hardening effect is caused by load transfer to the harder phase, which requires a certain connectivity/contiguity of the latter. The paper describes the extent of contiguity of the eutectic as well as the hard silicon and Al3Ni-phases within the eutectic, and discusses their contribution to an enhanced strength of Al-Si alloys at elevated temperatures.

Fracture toughness and high temperature strength of unidirectionally solidified Nb–Si binary and Nb–Ti–Si ternary alloys

2006 ◽  
Vol 425 (1-2) ◽  
pp. 223-229 ◽  
Author(s):  
Nobuaki Sekido ◽  
Yoshisato Kimura ◽  
Seiji Miura ◽  
Fu-Gao Wei ◽  
Yoshinao Mishima
Keyword(s):  
Fracture Toughness ◽  
High Temperature ◽  
Ternary Alloys ◽  
High Temperature Strength

scholarly journals Molybdenum Disilicide Composites Produced by Plasma Spraying

1998 ◽  
Author(s):  
R.G. Castro ◽  
H. Kung ◽  
K.J. Hollis ◽  
A.H. Bartlett
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Plasma Spraying ◽  
Creep Resistance ◽  
Elevated Temperatures ◽  
Powder Processing ◽  
National Laboratory ◽  
Molybdenum Disilicide ◽  
High Temperature Strength ◽  
Structural Applications

Abstract The intermetallic compound, molybdenum disilicide (MoSi2) is being considered for high temperature structural applications because of its high melting point and superior oxidation resistance at elevated temperatures. The lack of high temperature strength, creep resistance and low temperature ductility has hindered its progress for structural applications. Plasma spraying of coatings and structural components of MoSi2-based composites offers an exciting processing alternative to conventional powder processing methods due to superior flexibility and the ability to tailor properties. Laminate, discontinuous and in situ reinforced composites have been produced with secondary reinforcements of Ta, A1203, SiC, Si3N4 and Mo5Si3. Laminate composites, in particular, have been shown to improve the damage tolerance of MoSi2 during high temperature melting operations. A review of research which as been performed at Los Alamos National Laboratory on plasma spraying of MoSi2-based composites to improve low temperature fracture toughness, thermal shock resistance, high temperature strength and creep resistance will be discussed.

scholarly journals Nano-Scaled Creep Response of TiAlV Low Density Medium Entropy Alloy at Elevated Temperatures

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 36
Author(s):  
Xiangkai Zhang ◽  
Hanting Ye ◽  
Jacob C. Huang ◽  
Taiyou Liu ◽  
Pinhung Lin ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Peierls Stress ◽  
Dislocation Creep ◽  
Calphad Approach ◽  
Low Density ◽  
Face Centered Cubic ◽  
Specific Strength ◽  
Phase Constituent ◽  
Fcc Alloys ◽  
Face Centered

A low density, medium entropy alloy (LD-MEA) Ti33Al33V34 (4.44 g/cm3) was successfully developed. The microstructure was found to be composed of a disordered body-centered-cubic (BCC) matrix and minor ordered B2 precipitates based on transmission electron microscopy characterization. Equilibrium and non-equilibrium modeling, simulated using the Calphad approach, were applied to predict the phase constituent. Creep behavior of {110} grains at elevated temperatures was investigated by nanoindentation and the results were compared with Cantor alloy and Ti-6Al-4V alloy. Dislocation creep was found to be the dominant mechanism. The decreasing trend of hardness in {110} grains of BCC TiAlV is different from that in {111} grains of face-centered-cubic (FCC) Cantor alloy due to the different temperature-dependence of Peierls stress in these two lattice structures. The activation energy value of {110} grains was lower than that of {111} grains in FCC Cantor alloy because of the denser atomic stacking in FCC alloys. Compared with conventional Ti-6Al-4V alloy, TiAlV possesses considerably higher hardness and specific strength (63% higher), 83% lower creep displacement at room temperature, and 50% lower creep strain rate over the temperature range from 500 to 600 °C under the similar 1150 MPa stress, indicating a promising substitution for Ti-6Al-4V alloy as structural materials.

Surface Treatment of TiAl with Fluorine for Improved Performance at Elevated Temperatures

2008 ◽  
Vol 1128 ◽  
Author(s):  
A. Donchev ◽  
P.J. Masset ◽  
M. Schütze
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
Elevated Temperatures ◽  
Specific Weight ◽  
High Temperature Strength ◽  
Dramatic Improvement ◽  
Surface Zone ◽  
Automotive Engines ◽  
Halogen Effect ◽  
Improved Performance

AbstractAlloys based on aluminium and titanium are possible materials for several high temperature applications. The use of TiAl would increase the efficiency of e.g. aero turbines, automotive engines and others due to their properties, among others low specific weight and good high temperature strength. The oxidation resistance is low at temperatures above approximately 800°C so that no long term use of TiAl-components is possible without improvement of the oxidation behaviour. Small amounts of halogens in the surface zone of TiAl-samples lead to a dramatic improvement of the oxidation resistance at temperatures up to 1100°C for more than 8000 hours in air. In this paper results of the work on the halogen effect over the last years are presented. The results of thermogravimetric measurements, thermocyclic oxidation tests of small coupons and thermodynamic calculations for different atmospheres (e.g. air, H2O, SO2) are shown and the halogen effect mechanism is discussed. The postulated mechanism is in good agreement with the results of the oxidation tests. The limits of the halogen effect will also be mentioned. Predictions for the halogenation of TiAl-components can be given so that the processing can be planned in advance.

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