A study of pest oxidation in polycrystalline MoSi2

1992 ◽  
Vol 7 (10) ◽  
pp. 2747-2755 ◽  
Author(s):  
C.G. McKamey ◽  
P.F. Tortorelli ◽  
J.H. DeVan ◽  
C.A. Carmichael
Keyword(s):  
High Temperature ◽  
Melting Point ◽  
Stoichiometric Ratio ◽  
Low Density ◽  
High Melting ◽  
Phase Boundaries ◽  
High Melting Point ◽  
Good Oxidation Resistance ◽  
Intermediate Temperature Range ◽  
Physical Defects

MoSi2 is a promising high-temperature material with low density (6.3 g/cm3), high melting point (2020 °C), and good oxidation resistance at temperatures to about 1900 °C. However, in the intermediate temperature range between 400 and 600 °C, it is susceptible to a “pest” reaction which causes catastrophic disintegration by a combination of oxidation and fracture. In this study, we have used polycrystalline MoSi2, produced by arc-casting of the pure elements and by cold and hot pressing of alloy powders, to characterize the pest reaction and to determine the roles of composition, grain or phase boundaries, and physical defects on the oxidation and fracture of specimens exposed to air at 500 °C. It was found that pest disintegration occurs through transport of oxygen into the interior of the specimen along pre-existing cracks and/or pores, where it reacts to form MoO3 and SiO2. The internal stress produced during the formation of MoO3 results in disintegration to powder. Near the stoichiometric ratio, the susceptibility to pest disintegration increases with increasing molybdenum content and with decreasing density. Silicon-rich alloys were able to form protective SiO2 and showed no indication of disintegration, even at densities as low as 60%.

CRM MOLYBDENUM-50 RHENIUM

Alloy Digest ◽  
1970 ◽  
Vol 19 (12) ◽  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Powder Metallurgy ◽  
Melting Point ◽  
Physical Properties ◽  
Heat Treating ◽  
Electrical Contacts ◽  
High Melting ◽  
High Melting Point ◽  
Temperature Performance

Abstract CRM MOLYBDENUM-50 RHENIUM is a high-melting-point alloy for applications such as electronics tube components, electrical contacts, thermionic converters, thermocouples, heating elements and rocket thrusters. All products are produced by powder metallurgy. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as creep. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: Mo-11. Producer or source: Chase Brass & Copper Company Inc..

CRM RHENIUM

Alloy Digest ◽  
1970 ◽  
Vol 19 (8) ◽  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Powder Metallurgy ◽  
Melting Point ◽  
Heat Treating ◽  
Electrical Contacts ◽  
High Melting ◽  
High Melting Point ◽  
Temperature Performance ◽  
Commercially Pure

Abstract CRM RHENIUM is a commercially pure, high-melting-point metal for applications such as electronics tube components, electrical contacts, thermionic converters, thermocouples, heating elements and rocket thrusters. All products are produced by powder metallurgy. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as creep. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: Re-1. Producer or source: Chase Brass & Copper Company Inc..

Processing of Zinc-Based MgAl2O4 Composite and Effect of Fly Ash Addition

2007 ◽  
Vol 336-338 ◽  
pp. 1203-1206 ◽  
Author(s):  
Metin Gürü ◽  
M. Korçak ◽  
Süleyman Tekeli ◽  
Ahmet Güral
Keyword(s):  
Tensile Strength ◽  
Fly Ash ◽  
Melting Point ◽  
Low Density ◽  
High Melting ◽  
Spinel Oxide ◽  
High Melting Point ◽  
Corrosion Resistant ◽  
Coal Power ◽  
Resistant Composite Material

The properties of ceramic-metal (Cermet) composites as tensile strength, hardness and resistance to corrosion and high temperature are superior than ceramics and metals. Because of the enhanced characteristics of cermets, they are commonly used in various applications and industries. The main objective of this study is to produce a cheap, easy produced, strong and high corrosion resistant composite material. For these purposes, zinc is used for its natural capacity against corrosion, low density, low melting point and softness. Magnesium aluminates spinel oxide (MgAl2O4) is chosen because of its high melting point and low density. Fly ash is a waste from coal power plant having puzzolanic properties. In this study, the effect of various amounts of zinc and fly ash addition on density and hardness behaviour of zinc-based MgAl2O4 composites was investigated. The experimental results showed that zinc and fly ash addition improved the hardness behavior of zincbased MgAl2O4 composite.

Effect of Transition Metal Silicides on Microstructure and Mechanical Properties of Ultra-High Temperature Ceramics

2013 ◽  
pp. 125-179 ◽  
Author(s):  
Laura Silvestroni ◽  
Diletta Sciti
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Melting Point ◽  
Leading Edge ◽  
High Melting ◽  
High Melting Point ◽  
Ultra High Temperature Ceramics ◽  
Sintering Additives ◽  
Self Diffusion ◽  
Ultra High Temperature

The IV and V group transition metals borides, carbides, and nitrides are widely known as ultra-high temperature ceramics (UHTCs), owing to their high melting point above 2500°C. These ceramics possess outstanding physical and engineering properties, such as high hardness and strength, low electrical resistivity and good chemical inertness which make them suitable structural materials for applications under high heat fluxes. Potential applications include aerospace manufacturing; for example sharp leading edge parts on hypersonic atmospheric re-entry vehicles, rocket nozzles, and scramjet components, where operating temperatures can exceed 3000°C. The extremely high melting point and the low self-diffusion coefficient make these ceramics very difficult to sinter to full density: temperatures above 2000°C and the application of pressure are necessary conditions. However these processing parameters lead to coarse microstructures, with mean grain size of the order of 20 µm and trapped porosity, all features which prevent the achievement of the full potential of the thermo-mechanical properties of UHTCs. Several activities have been performed in order to decrease the severity of the processing conditions of UHTCs introducing sintering additives, such as metals, nitrides, carbides or silicides. In general the addition of such secondary phases does decrease the sintering temperature, but some additives have some drawbacks, especially during use at high temperature, owing to their softening and the following loss of integrity of the material. In this chapter, composites based on borides and carbides of Zr, Hf and Ta were produced with addition of MoSi2 or TaSi2. These silicides were selected as sintering aids owing to their high melting point (>2100°C), their ductility above 1000°C and their capability to increase the oxidation resistance. The microstructure of fully dense hot pressed UHTCs containing 15 vol% of MoSi2 or TaSi2, was characterized by x-ray diffraction, scanning, and transmission electron microscopy. Based on microstructural features detected by TEM, thermodynamical calculations, and the available phase diagrams, a densification mechanism for these composites is proposed. The mechanical properties, namely hardness, fracture toughness, Young’s modulus and flexural strength at room and high temperature, were measured and compared to the properties of other ultra-high temperature ceramics produced with other sintering additives. Further, the microstructural findings were used to furnish possible explanations for the excellent high temperature performances of these composites.

Hot Pressing and Characterization of ZrB2-SiC-MoSi2 Composite

2015 ◽  
Vol 830-831 ◽  
pp. 421-424
Author(s):  
T. Venkateswaran ◽  
M. Agilan ◽  
D. Sivakumar ◽  
Bhanu Pant
Keyword(s):  
High Temperature ◽  
Melting Point ◽  
Oxidation Resistance ◽  
Hot Pressing ◽  
Mechanical And Thermal Properties ◽  
High Melting ◽  
Hafnium Diboride ◽  
High Melting Point ◽  
Microstructural Investigation ◽  
Ultra High Temperature

Transition metal diborides, especially zirconium and hafnium diboride are potential ceramic material for ultra high temperature applications above 1800°C. These borides are characterized by high melting point, formation of high melting point oxides, good oxidation resistance and excellent thermo-mechanical properties. In this present exploration, zirconium diboride (ZrB2) has been selected for its moderate density (6.09 gm/cc) and better oxidation resistance compared to high density hafnium diboride (11.2 gm/cc). The developed ZrB2 composite in the present study contains 10 wt. % SiC and 10 wt. % MoSi2 as sintering additives. SiC and MoSi2 were added to improve the thermal shock resistance and sinterability of the ultra high temperature ceramics (UHTCs). Vacuum hot pressing was carried out at 1800°C for a holding period of 30 minutes and applied pressure of 30 MPa. Attractive feature of this ZrB2 composite is good machinability due to better electrical conductivity and complicated shapes can be realized easily through electro discharge machining (EDM) process. Detailed XRD phase analysis and microstructural investigation of the polished and fractured composites was carried out using SEM. Mechanical and thermal properties tests have been carried out for the optimized ZrB2 composite material.

Thermoelectric characteristics of high-temperature thermocouples with electrodes made of high melting point alloys

1961 ◽  
Vol 4 (5) ◽  
pp. 366-369
Author(s):  
P. S. Kislyi ◽  
V. I. Lakh ◽  
G. V. Samsonov ◽  
B. I. Stadnyk ◽  
R. F. Kharenko ◽  
...  
Keyword(s):  
High Temperature ◽  
Melting Point ◽  
High Melting ◽  
High Melting Point

scholarly journals Preparation of single crystal wires of metals of high melting point

1937 ◽  
Vol 163 (912) ◽  
pp. 16-18 ◽  
Keyword(s):  
High Temperature ◽  
Melting Point ◽  
Temperature Gradient ◽  
Single Crystal ◽  
Recrystallization Temperature ◽  
High Melting ◽  
High Melting Point ◽  
High Temperature Furnaces ◽  
Very High ◽  
A Current

Various methods of preparing single crystal wires of metals have been devised (see, e. g. Schmid and Boas 1935; Andrade and Roscoe 1937), but they all demand furnaces which reach the melting point, the transformation point, or the recrystallization temperature of the metal. In the case of metals where the temperature in question is very high the general methods call, then, for high temperature furnaces which are costly and often troublesome to control. The method to be described eliminates the need of such a furnace, and would seem to have a wide application. The wire is maintained at a high temperature by a current passing through it, and a subsidiary temperature gradient is applied.

Photoswitching the melting point of a semicrystalline polymer by the azobenzene terminal group for reversible solid-to-liquid transition

2021 ◽  
Author(s):  
Bin Dong ◽  
Hui Zhang ◽  
Yutong Guo ◽  
Jie Xiao ◽  
Yunyu Sun ◽  
...  
Keyword(s):  
High Temperature ◽  
Melting Point ◽  
Daily Life ◽  
Terminal Group ◽  
Semicrystalline Polymer ◽  
High Melting ◽  
High Melting Point ◽  
Crystalline Polymers ◽  
Liquid Transition

Semi-crystalline polymers are widely used in daily life. However, due to its high melting point, its processing normally requires the application of high temperature or the addition of plasticizers. Here,...

CLIMELT MOLYBDENUM

Alloy Digest ◽  
1970 ◽  
Vol 19 (10) ◽  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Melting Point ◽  
Physical Properties ◽  
Heat Treating ◽  
Electrical Contacts ◽  
High Melting ◽  
High Melting Point ◽  
Temperature Performance ◽  
Commercially Pure

Abstract CLIMELT MOLYBDENUM is a commercially pure high melting point metal for applications such as electronic tube components, electric furnace elements, electrical contacts, and electrodes. It is produced by arc casting. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as creep. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Mo-10. Producer or source: Climax Molybdenum Company of Michigan, American Metal Climax.

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