Differences in growth mechanisms of oxide scales formed on ODS and conventional wrought alloys

Quadakkers, W. J.; Holzbrecher, H.; Briefs, K. G.; Beske, H. E.

doi:10.1007/bf00665269

Cited by 249 publications

(100 citation statements)

References 18 publications

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“…The addition of yttrium in conventional alloys has been shown to increase scale adherence by the formation of "pegs" or protrusions formed around the rare-earth-metal containing particles extending from the oxide scale into the metal, pinning the scale to the underlying metal. Quadakkers et al (1989) evaluated the oxidation mechanism of Alloy MA956 in synthetic air at 1830 and 2010 °F (1000 and 1100 °C) tagging the gaseous environment with radioactive 18 O to study the scale growth mechanism. Yttrium-containing phases were incorporated into the scale improving scale adherence and reducing scale growth rate.…”

Section: -4mentioning

confidence: 99%

“…The effective role of yttria in scale growth and adherence was sensitive to the appropriate amount and distribution of the oxide dispersion. High amounts of yttria have been associated with thicker oxide scales due to enhanced inward growth (Quadakkers, 1989).…”

Section: -4mentioning

confidence: 99%

“…The entrapped or absorbed dispersoid reduces diffusion of cations through the scale with oxide growth taking place at the scale-metal interface by exclusive inward oxygen transport with minimal growth stresses from alumina nucleation within the existing scale (Quadakkers, 1989). The presence of yttrium at the scale grain boundaries retards grain boundary migration resulting in fine grain scales where growth stress are more effectively relieved by diffusional plastic flow improving scale adherence (Malik, 1990).…”

Section: -4mentioning

confidence: 99%

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Combustion 2000

Levasseur¹,

Goodstine²,

Ruby³

et al. 2001

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. The objective of this report is to emphasize the results and achievements of the program and not to archive every detail of the past six years of effort. These details are already available in the twenty-two quarterly reports previously submitted to DOE and in the final report from Phase I. The report is divided into three major foci, indicative of the three operational groupings of the program as it evolved, was restructured, or overtaken by events. In each of these areas, the results exceeded DOE goals and expectations.HIPPS Systems and Cycles (including thermodynamic cycles, power cycle alternatives, baseline plant costs and new opportunities) HITAF Components and Designs (including design of heat exchangers, materials, ash management and combustor design)Testing Program for Radiative and Convective Air Heaters (including the design and construction of the test furnace and the results of the tests)There are several topics that were part of the original program but whose importance was diminished when the contract was significantly modified. The elimination of the subsystem testing and the Phase III demonstration lessened the relevance of subtasks related to these efforts. For example, the cross flow mixing study, the CFD modeling of the convective air heater and the power island analysis are important to a commercial plant design but not to the R&D product contained in this report. These topics are of course, discussed in the quarterly reports under this contract.The DOE goal for the High Performance Power Plant System ( HIPPS ) is high thermodynamic efficiency and significantly reduced emissions. Specifically, the goal is a 300 MWe plant with > 47% (HHV) overall efficiency and ≤ 0.1 NSPS emissions. This plant must fire at least 65% coal with the balance being made up by a premium fuel such as natural gas.To achieve these objectives requires a change from complete reliance of coal-fired systems on steam turbines (Rankine cycles) and moving forward to a combined cycle utilizing gas turbines (Brayton cycles) which offer the possibility of significantly greater efficiency. This is because gas turbine cycles operate at temperatures well beyond current steam cycles, allowing the working fluid (air) temperature to more closely approach that of the major energy source, the combustion of coal. In fact, a good figure of merit for a HIPPS design is just how much of the enthalpy from coal combustion is used by the gas turbine.The efficiency of a power cycle varies directly with the temperature of the working fluid and for contemporary gas turbines the optimal turbine inlet temperature is in the range of 2300-2500 °F (1260-1371 °C). These temperatures are beyond the working range of currently available alloys and are also in the range of the ash fusion temperature of most coals. These two sets of physical properties combine to produce the major engineering challenges for a HIPPS design. ivThe UTRC team developed a design hierarchy to impose more rigor in our approach. Once the size of the plant had been determined by t...

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Section: -4mentioning

confidence: 99%

Section: -4mentioning

confidence: 99%

Section: -4mentioning

confidence: 99%

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Combustion 2000

Levasseur¹,

Goodstine²,

Ruby³

et al. 2001

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“…For the past 25 years, it has been generally recognized that transport through a growing a-Al 2 O 3 scale takes place predominantly by the inward diffusion of O along grain boundaries when a reactive element (RE) is present [1][2][3][4][5][6][7][8][9][10][11]. Without a RE addition, a mixed Al and O growth was observed for a-Al 2 O 3 .…”

Section: Introductionmentioning

confidence: 99%

Grain Boundary Chemistry and Transport Through Alumina Scales on NiAl Alloys

et al. 2017

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It is widely accepted that the growth of protective a-Al 2 O 3 scales on Nibased alloys is governed by the inward diffusion of oxygen through the oxide grain boundaries (GB). However, there is also some outward diffusion of metal ions to the surface, but it is difficult to quantify. In this work we apply atomic force microscopy, scanning electron microscopy and transmission electron microscopy to investigate the outward flux of Al, which manifests as the growth of small ridges along the alumina GBs after the removal of the outermost oxide layer by mechanical polishing or focused ion beam techniques followed by additional oxidation. As a model alumina-former, NiAl with Hf and Zr additions was investigated. In comparison to Zr, Hf was found to reduce the outward Al diffusion. This outward diffusion was six orders of magnitude smaller than the O inward diffusion.

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“…O óxido protetor formado em altas temperaturas é a alumina (Quadakkers et al, 1989e Huntz et al, 1998, ao contrário da maioria das superligas, onde o óxido é do tipo cromia. Ginesan e Smith (Ginesan e Smith, 1988) estudaram a resistência à oxidação de seis superligas (Inconel 617, Inco HX, Nimonic 86, Haynes 188, Haynes 214 e MA 956) em vários meios e observaram que a Incoloy MA 956 apresentou desempenho excepcional em todas as condições.…”

Section: Incoloy Ma 956unclassified

Corrosão de aços inoxidáveis avançados em meios fisiológicos

Terada¹

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were rich in chromium and iron. The electrochemical behavior of these steels was investigated using electrochemical impedance spectroscopy (EIE), potentiodynamic polarization, scanning vibrating electrode technique (SVET), field emission gun (FEG), scanning electrochemical microscopy (SECM), optical microscopy (OM) and scanning electron microscopy (SEM). The test electrolytes used were Hanks solution, a culture medium known as Minimum Essential Medium (MEM) and a buffered phoshated solution (PBS). The EIE results were interpreted using equivalent electrical circuits that simulated the duplex structure of the oxide layer. All the materials were more resistant to localized corrosion than AISI 316L, with composition similar to ASTM F-138 SS. The results also highlighted the effect of the solution annealing treatment on corrosion resistance of the high nitrogen DIN W. Nr. 1.4460.The DIN W. Nr. 1.4970 steel was cytotoxic. Hence it cannot be used as a biomaterial.The DIN W. Nr. 1.4575 steel and Incoloy MA 956 can only be used for applications of easy removal, such as for odontological prostheses, due to their ferromagnetic properties. The DIN W. Nr. 1.4460 (0.87% nitrogen) steel was the SS with the best properties, among those studied for use as biomaterials.

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Differences in growth mechanisms of oxide scales formed on ODS and conventional wrought alloys

Cited by 249 publications

References 18 publications

Combustion 2000

Combustion 2000

Grain Boundary Chemistry and Transport Through Alumina Scales on NiAl Alloys

Corrosão de aços inoxidáveis avançados em meios fisiológicos

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