Phase Stability in Cast HP Austenite After Long-Term Ageing

2000 ◽  
Vol 6 (S2) ◽  
pp. 352-353
Author(s):  
E.A. Kenik ◽  
P.J. Maziasz
Keyword(s):  
High Temperature ◽  
Phase Distribution ◽  
Grain Boundary Sliding ◽  
Steam Superheater ◽  
Second Phase ◽  
Cast Material ◽  
Centrifugally Cast ◽  
The Stability ◽  
Term Creep

Casting of high temperature austenitic alloys is often used to form components and structures required in the chemical industry. Alloy HP is a Nb-stabilized austenitic alloy for such applications. High carbon levels are selected in order to drive the formation of coarse, intergranular precipitates of various carbides. These precipitates provide resistance to high temperature creep by inhibiting grain boundary sliding. While these precipitates are present in the cast material prior to high temperature exposure, it is the stability of these second phase particles during ageing that determines the long-term creep resistance and lifetime of stressed components. This study deals with the phase distribution in a centrifugally-cast HP component from a steam superheater tube in a styrene furnace, which experienced temperatures from 927°C to 1066°C or more for over 105,000 h.

Microstructural characterization of a rapidly solidified Al-Fe-V-Si alloy for elevated temperature applications

1988 ◽  
Vol 46 ◽  
pp. 550-551
Author(s):  
R. E. Franck ◽  
J. A. Hawk ◽  
G. J. Shiflet
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Grain Growth ◽  
Volume Fraction ◽  
Microstructural Characterization ◽  
Second Phase ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Temperature Applications

Rapid solidification processing (RSP) is one method of producing high strength aluminum alloys for elevated temperature applications. Allied-Signal, Inc. has produced an Al-12.4 Fe-1.2 V-2.3 Si (composition in wt pct) alloy which possesses good microstructural stability up to 425°C. This alloy contains a high volume fraction (37 v/o) of fine nearly spherical, α-Al12(Fe, V)3Si dispersoids. The improved elevated temperature strength and stability of this alloy is due to the slower dispersoid coarsening rate of the silicide particles. Additionally, the high v/o of second phase particles should inhibit recrystallization and grain growth, and thus reduce any loss in strength due to long term, high temperature annealing.The focus of this research is to investigate microstructural changes induced by long term, high temperature static annealing heat-treatments. Annealing treatments for up to 1000 hours were carried out on this alloy at 500°C, 550°C and 600°C. Particle coarsening and/or recrystallization and grain growth would be accelerated in these temperature regimes.

Microstructural Instability in Mosi2/Sic Nanolayers

1997 ◽  
Vol 3 (S2) ◽  
pp. 399-400
Author(s):  
Y.C. Lu ◽  
H. Kung ◽  
J-P Hirvonen ◽  
T.R. Jervis ◽  
M. Nastasi ◽  
...  
Keyword(s):  
High Temperature ◽  
Ion Irradiation ◽  
High Temperature Strength ◽  
Second Phase ◽  
Microstructural Stability ◽  
Factors Affecting ◽  
Structural Applications ◽  
Thermal Compatibility ◽  
Two Phases ◽  
The Stability

Thin film multilayers have been the focus of extensive studies recently due to the interesting properties they exhibit. Since the improvement in properties can be attributed directly to the unique nanoscale microstructures, it is essential to understand the factors affecting the microstructural stability in these nanolayer structures. The intermetallic compound, MoSi2, despite its superior oxidation resistance and high melting point, suffers from inadequate high temperature strength and low temperature ductility, properties which hinder its high temperature structural applications [1]. SiC is a potential second phase reinforcement due to its high temperature strength and thermal compatibility with MoSi2. The addition of SiC in a nanolayered configuration has been shown to exhibit significant increase in hardness after annealing [2]. It has also been shown that when annealed above 900°C, the layers break down and grain growth sets in, with a significant decrease in hardness and. Due to the lack of a thermochemical driving force, the two phases remain separate at all temperatures investigated. In this study, the stability of the MoSi2/SiC nanolayers structure under ion irradiation has been investigated.

Metallurgy and Behavior of Alloys for Reformer Furnaces

2007 ◽  
Author(s):  
Carl E. Jaske
Keyword(s):  
High Temperature ◽  
Material Properties ◽  
Material Behavior ◽  
High Temperature Creep ◽  
Centrifugally Cast ◽  
Resistance To Oxidation ◽  
Long Term Performance ◽  
And Behavior ◽  
Term Performance

This paper reviews the metallurgy and behavior of centrifugally cast heat-resistant alloys for ammonia, methanol, and hydrogen reformer furnaces. The alloys include HK and HP, as well as proprietary versions of these materials produced by various foundries. Alloying and metallurgical factors that affect resistance to oxidation, carburization, and high temperature creep are discussed. Examples of the effects of environment and temperature on material behavior are provided. Finally, the use of material properties to predict the long-term performance of reformer furnace components is reviewed.

scholarly journals Long-Term Creep Properties of Hastelloy XR in Simulated High-Temperature Gas-Cooled Reactor Helium

1995 ◽  
Vol 32 (11) ◽  
pp. 1108-1117 ◽  
Author(s):  
Yuji KURATA ◽  
Yutaka OGAWA ◽  
Tomio SUZUKI ◽  
Masami SHINDO ◽  
Hajime NAKAJIMA ◽  
...  
Keyword(s):  
High Temperature ◽  
Creep Properties ◽  
Term Creep ◽  
High Temperature Gas

The Tensile Strength of Glass Yarn in Rubber. II. The Effects of Normal Humidities

1972 ◽  
Vol 45 (1) ◽  
pp. 49-59 ◽  
Author(s):  
R. A. Gregg
Keyword(s):  
Tensile Strength ◽  
High Temperature ◽  
Glass Composite ◽  
Moisture Index ◽  
Permanent Loss ◽  
Dry Conditions ◽  
The Stability ◽  
Moisture Conditions ◽  
High Temperature Drying

Abstract The resinous impregnant in glass yarn influences the stability of the yarn. Some glass yarns suffer tensile degradation on storage and/or vulcanization at high humidities. One type of glass yarn was exposed in atmospheres over the range 0–88% relative humidity at 73° F for times up to 400 days. Tensile losses of 30% or more can occur on storage of the glass yarn at the humidities in the upper end of the range. This loss is permanent as even vigorous drying at high temperatures will not restore the tensile. Under dry conditions the yarn has excellent storage stability. Furthermore, after vulcanization even into thin composites, the glass yarn shows only a small permanent loss of tensile under moisture conditions that would seriously degrade the yarn in a package. An increased degree of vulcanization of the rubber slightly increases the tensile strength of the composite. In addition to its permanent degradative action in long-term exposure, water has a phenomenological effect of reducing glass composite tensile by its presence. A tensile sensitivity to moisture index is suggested and used to characterize the glass yarn. This tensile loss is recoverable by drying but some of the water is bound very tightly. Thin composites do not give up all of the water in 150 days over Drierite® as shown by the fact that more vigorous high temperature drying leads to a further increase in tensile strength. Tensile strength at 300° F is about 25% lower than at 73° F at any moisture content. Higher moisture contents lead to lower absolute tensiles. Tensile values are detailed for conditions that might exist during cure or in a product running at a high temperature. The high temperature incurred tensile reductions from a standard tensile are significant and should be considered in designing products. The detailed observations apply only to this particular glass yarn but the principles and methods are applicable in the evaluation or development of any glass yarn.

Design Methodologies for High Temperature Reactor Structural Components Cladded With Noncompliant Materials

2019 ◽  
Author(s):  
B. Barua ◽  
V.-T. Phan ◽  
M. C. Messner ◽  
B. Jetter ◽  
T.-L. Sham ◽  
...  
Keyword(s):  
High Temperature ◽  
Base Material ◽  
Design Rules ◽  
Corrosion Resistant ◽  
Class A ◽  
Creep Fatigue ◽  
The Difference ◽  
Near Term ◽  
Term Creep

Abstract The existing Class A metallic materials qualified for ASME Section III, Division 5 rules for high temperature nuclear reactors, are not optimized for corrosion resistance when exposed to corrosive reactor coolants such as molten salts, and molten lead and lead-bismuth eutectic. Introducing new corrosion-resistant materials into the Code would be a lengthy and expensive process for long design lifetimes, requiring long-term creep test data. A near-term alternative solution might be to allow designers to clad the existing Class A materials with thin layer of some corrosion-resistant material. However, the current ASME Section III, Division 5 rules provide no guidance on evaluating cladded components against the Code creep-fatigue or strain limits requirements. This necessitates the development of design rules for cladded components that do not require long-term testing of clad materials. Depending on the difference in mechanical properties, the influence of clad on the long term response of the structural system can be significant or negligible. This work focuses on developing design rules for cladded components with a clad material that does not accumulate significant inelastic deformation compared to the base material. This work proposes to treat such clad materials as linear elastic. Sample calculations including finite element analyses of a representative molten salt reactor heat exchanger tube without and with clad were performed to verify the proposed approach. Finally, a complete set of design rules for components with noncompliant clad material is proposed.

KUBOTA ALLOY HN

Alloy Digest ◽  
2010 ◽  
Vol 59 (4) ◽  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Oxidation Resistance ◽  
Temperature Performance ◽  
Term Creep ◽  
Rupture Properties ◽  
Better Than

Abstract Kubota alloy HN is an austenitic Fe-Ni-Cr alloy with long-term creep-rupture properties that are intermediate between those of HK40 and HP40 alloys. Carburization resistance is better than that of HK40, but oxidation resistance is generally lower, making the alloy suitable for long service at 1095 deg C (2000 deg F). This datasheet provides information on composition, physical properties, and tensile properties as well as creep. It also includes information on high temperature performance and corrosion resistance as well as casting, machining, and joining. Filing Code: SS-1060. Producer or source: Kubota Metal Corporation, Fahramet Division.

Impression Creep Behavior of Atmospheric Plasma-Sprayed and Hot Pressed MoSi2/Si3N4

1997 ◽  
Author(s):  
K.J. Hollis ◽  
D.P. Butt ◽  
R.G. Castro
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
Creep Behavior ◽  
Grain Boundary Sliding ◽  
Atmospheric Plasma ◽  
Second Phase ◽  
Impression Creep ◽  
Creep Mechanisms ◽  
Boundary Sliding ◽  
Plasma Sprayed

Abstract The use of MoSi2 as a high temperature oxidation resistant structural material is hindered by its poor elevated temperature creep resistance. The addition of second phase Si3N4 holds promise for improving the creep properties of MoSi2 without decreasing oxidation resistance. The high temperature impression creep behavior of atmospheric plasma sprayed (APS) and hot pressed (HP) MoSi2/Si3N4 composites was investigated. Values for steady state creep rates, creep activation energies, and creep stress exponents were measured. Grain boundary sliding and splat sliding were found to be the dominant creep mechanisms for the APS samples while grain boundary sliding and plastic deformation were found to be the dominant creep mechanisms for the HP samples.

An evaluation of anion suitability for use in ionic liquids with long-term, high-temperature thermal stability

2017 ◽  
Vol 41 (16) ◽  
pp. 7844-7848 ◽  
Author(s):  
Adela Benchea ◽  
Benjamin Siu ◽  
Mohammad Soltani ◽  
JaMichael H. McCants ◽  
E. Alan Salter ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Ionic Liquids ◽  
High Temperature ◽  
The Stability

The stability of fourteen different PPN+ salts has been studied in 96 hour tests, in air, at temperatures of 200 °C, 250 °C, and 300 °C.

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