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.

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.

WC-Ta-10W

Alloy Digest ◽  
1970 ◽  
Vol 19 (12) ◽  
Keyword(s):  
Fracture Toughness ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Low Temperature ◽  
Physical Properties ◽  
Elevated Temperatures ◽  
Base Alloy ◽  
Heat Treating ◽  
Temperature Performance ◽  
Structural Applications

Abstract WC Ta-10W is a tantalum-base alloy having a combination of low-temperature ductility and fabricability in both the recrystalilzed and wrought conditions, as well as excellent weld ductility. Developed originally for structural applications at elevated temperatures, it is now available in a complete line of aerospace hardware. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as fracture toughness and creep. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Ta-1. Producer or source: Teledyne Wah Chang Albany.

Characterization of the Phase Evolution of Mosi2 - TiB2 Composites Produced by In-Situ Reactions Using Scanning Electron Microscopy (SEM), Electron Probe Microanalysis (EPMA), and X-Ray Diffraction (XRD)

2000 ◽  
Vol 6 (S2) ◽  
pp. 374-375
Author(s):  
L. A. Dempere ◽  
M. J. Kaufman
Keyword(s):  
High Temperature ◽  
Elevated Temperatures ◽  
Mechanical Performance ◽  
Molybdenum Disilicide ◽  
Phase Evolution ◽  
Secondary Phases ◽  
Temperature Oxidation ◽  
Structural Applications ◽  
In Situ Reactions

Intermetallics are playing an important role in the development of new materials able of sustaining the escalating demands of the aerospace industry. A significant improvement in weight, operating temperatures or mechanical performance is required for materials to be considered as replacements in the most demanding applications. Molybdenum disilicide is one such compound that has potential for high temperature applications. Its most attractive properties are its high melting point (2020°C), reasonable density (6.24 g/cm3), and excellent high temperature oxidation and corrosion resistance. However, low ambient fracture toughness and loss of strength at elevated temperatures have been the most significant limitations to the use of MoSi2 in structural applications.The more promising solutions for improving the mechanical properties of brittle intermetallics such as MoSi2 are based on the incorporation and control of secondary phases. To date, the artificial introduction of reinforcing phases or their generation via in-situ reactions have been explored.

Lattice Imaging of Grain Boundaries in Ceramics

1977 ◽  
Vol 35 ◽  
pp. 114-115
Author(s):  
D. R. Clarke ◽  
G. Thomas
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Grain Boundaries ◽  
High Temperature Strength ◽  
Current Interest ◽  
Lattice Imaging ◽  
Special Significance ◽  
Structural Applications ◽  
Refractory Ceramics

Grain boundaries have long held a special significance to ceramicists. In part, this has been because it has been impossible until now to actually observe the boundaries themselves. Just as important, however, is the fact that the grain boundaries and their environs have a determing influence on both the mechanisms by which powder compaction occurs during fabrication, and on the overall mechanical properties of the material. One area where the grain boundary plays a particularly important role is in the high temperature strength of hot-pressed ceramics. This is a subject of current interest as extensive efforts are being made to develop ceramics, such as silicon nitride alloys, for high temperature structural applications. In this presentation we describe how the techniques of lattice fringe imaging have made it possible to study the grain boundaries in a number of refractory ceramics, and illustrate some of the findings.

DOWMETAL HZ32XA

Alloy Digest ◽  
1956 ◽  
Vol 5 (7) ◽  
Keyword(s):  
High Temperature ◽  
Physical Properties ◽  
Creep Resistance ◽  
Zirconium Alloy ◽  
Elevated Temperatures ◽  
Heat Treating ◽  
High Temperature Creep ◽  
Aged Condition ◽  
Chemical Company ◽  
Temperature Performance

Abstract DOWMETAL HZ32XA is a magnesium-thorium-zinc-zirconium alloy having good high temperature creep resistance, and is recommended for applications at elevated temperatures. It is used in the artificially aged condition (T5). This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as creep. It also includes information on high temperature performance as well as heat treating, machining, and joining. Filing Code: Mg-26. Producer or source: The Dow Chemical Company.

The Application of X-Ray Diffraction at Elevated Temperatures to Study the Mechanism of Formation of Sodium Tripolyphosphate

1961 ◽  
Vol 5 ◽  
pp. 276-284
Author(s):  
E. L. Moore ◽  
J. S. Metcalf
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Amorphous Phase ◽  
Elevated Temperatures ◽  
Sodium Tripolyphosphate ◽  
X Ray Diffraction ◽  
Mechanism Of Formation ◽  
X Ray ◽  
Temperature Form ◽  
High Temperature Form

AbstractHigh-temperature X-ray diffraction techniques were employed to study the condensation reactions which occur when sodium orthophosphates are heated to 380°C. Crystalline Na4P2O7 and an amorphous phase were formed first from an equimolar mixture of Na2HPO4·NaH2PO4 and Na2HPO4 at temperatures above 150°C. Further heating resulted in the formation of Na5P3O10-I (high-temperature form) at the expense of the crystalline Na4P4O7 and amorphous phase. Crystalline Na5P3O10-II (low-temperature form) appears after Na5P3O10-I.Conditions which affect the yield of crystalline Na4P2O7 and amorphous phase as intermediates and their effect on the yield of Na5P3O10 are also presented.

scholarly journals Development of Creep-Resistant, Alumina-Forming Ferrous Alloys for High-Temperature Structural Use

2018 ◽  
Author(s):  
Y. Yamamoto ◽  
M. P. Brady ◽  
G. Muralidharan ◽  
B. A. Pint ◽  
P. J. Maziasz ◽  
...  
Keyword(s):  
High Temperature ◽  
Elevated Temperatures ◽  
Extreme Environments ◽  
Alloy Design ◽  
Austenitic Steels ◽  
Strength Development ◽  
Second Phase ◽  
Ferrous Alloys ◽  
Steel Alloys ◽  
Structural Applications

This paper overviews recent advances in developing novel alloy design concepts of creep-resistant, alumina-forming Fe-base alloys, including both ferritic and austenitic steels, for high-temperature structural applications in fossil-fired power generation systems. Protective, external alumina-scales offer improved oxidation resistance compared to chromia-scales in steam-containing environments at elevated temperatures. Alloy design utilizes computational thermodynamic tools with compositional guidelines based on experimental results accumulated in the last decade, along with design and control of the second-phase precipitates to maximize high-temperature strengths. The alloys developed to date, including ferritic (Fe-Cr-Al-Nb-W base) and austenitic (Fe-Cr-Ni-Al-Nb base) alloys, successfully incorporated the balanced properties of steam/water vapor-oxidation and/or ash-corrosion resistance and improved creep strength. Development of cast alumina-forming austenitic (AFA) stainless steel alloys is also in progress with successful improvement of higher temperature capability targeting up to ∼1100°C. Current alloy design approach and developmental efforts with guidance of computational tools were found to be beneficial for further development of the new heat resistant steel alloys for various extreme environments.

Pest Resistant and Low CTE MoSi2-Matrix for High Temperature Structural Applications

1994 ◽  
Vol 350 ◽  
Author(s):  
M. G. Hebsur
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Matrix Composition ◽  
Temperature Oxidation ◽  
Accelerated Oxidation ◽  
Structural Applications ◽  
Base Matrix ◽  
Sic Reinforcement

AbstractThe objective of this investigation was to identify a pest resistant MoSi2-base matrix composition having properties suitable for SiC reinforcement. A 30 vol.% addition of fine Si3N4 particulates to MoSi2 significantly improved the low temperature accelerated oxidation resistance and thereby eliminated pest failure. Addition of Si3N4 also improved the high temperature oxidation resistance, strength and more importantly lowered the CTE of MoSi2 such that cracking was eliminated in a hybrid composite consisting of 30 vol.% Si3N4 and 30 vol. % SCS-6 fibers.

Mechanical Behavior of 2D C/SiC Composites at Elevated Temperatures under Uniaxial Compression

2011 ◽  
Vol 462-463 ◽  
pp. 1-6 ◽  
Author(s):  
Tao Suo ◽  
Yu Long Li ◽  
Ming Shuang Liu
Keyword(s):  
Compressive Strength ◽  
High Temperature ◽  
Carbon Fiber ◽  
Mechanical Behavior ◽  
Uniaxial Compression ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Carbon Matrix ◽  
Structural Applications ◽  
Sic Composites

As Carbon-fiber-reinforced SiC-matrix (C/SiC) composites are widely used in high-temperature structural applications, its mechanical behavior at high temperature is important for the reliability of structures. In this paper, mechanical behavior of a kind of 2D C/SiC composite was investigated at temperatures ranging from room temperature (20C) to 600C under quasi-static and dynamic uniaxial compression. The results show the composite has excellent high temperature mechanical properties at the tested temperature range. Catastrophic brittle failure is not observed for the specimens tested at different strain rates. The compressive strength of the composite deceases only 10% at 600C if compared with that at room temperature. It is proposed that the decrease of compressive strength of the 2D C/SiC composite at high temperature is influenced mainly by release of thermal residual stresses in the reinforced carbon fiber and silicon carbon matrix and oxidation of the composite in high temperature atmosphere.

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.

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