Development of oxidation resistant high temperature intermetallics

Grabke, H. J.; Brumm, M. W.; Steinhorst, M.

doi:10.1179/026708392790170892

Cited by 6 publications

(5 citation statements)

References 8 publications

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“…It is, therefore, somewhat surprising that, until recently, there has been only a limited number of studies devoted to gaining a theoretical or experimental understanding of the oxidation behavior of multiphase alloys from the viewpoint of elucidating the role of the individual phases. [37][38][39][40][41][42][43][44] From a thermodynamic standpoint, it is worth noting that there is no distinction between the chemical stability of an element in a single-phase alloy versus a multiphase alloy. This is because equilibrium considerations require that the chemical activity of any given component must be the same in all phases of a multiphase alloy, regardless of how large the concentration difference may be.…”

Section: Oxidation Of Two-phase Alloysmentioning

confidence: 99%

Alloy design strategies for promoting protective oxide-scale formation

Brady

Wright

Gleeson

2000

JOM

194

105

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Figure 1. A scanning electron microscopy (backscatter mode) cross-section micrograph of Nb-33Ti-40Al (in at.%) after 15 minutes at 1,400°C in air. The continuous Al 2 O 3 scale cuts off the formation of more rapidly growing niobium-rich transient oxides. 3 5 µm with the thermochemistry of the environment and the temperature of the reaction. Oxidation can lead to a loss of load-bearing capacity in a component by the reduction of metallic cross section and, for many high-temperature applications, is the primary factor limiting service life. Interstitial dissolution of oxygen, nitrogen, etc. into an alloy during elevated-temperature exposure, which may accompany oxidation, can also degrade mechanical properties and result in component failure.In practice, the oxidation of metals in many applications is not prevented, rather it is managed. Protection of the underlying metal is most often accomplished by the formation of a continuous scale over the surface such that it serves as a barrier between the remaining underlying, unoxidized metal and the environment. Long-term protection is generally associated with a scale that grows by a diffusion-controlled process or processes because the rate of scale growth slows with reaction time as the diffusion distance (scale thickness) increases. Most high-temperature environments of technological interest contain at least some oxygen. Given the fact that metal oxides are nearly always more stable thermoEditor's Note: Compositions are given in weight percent unless otherwise noted.This article discusses general strategies for designing alloys to form protective oxide scales. Approaches based on classical alloyoxidation theories work reasonably well for single-phase alloys. However, high-temperature alloy development has been and will increasingly be based on multiphase microstructures in order to achieve many of the needed, but usually opposing properties, such as high-temperature strength and room-temperature toughness. No theoretical-based, well-defined strategies exist for the design of oxidation-resistant multiphase alloys. Still, key factors are beginning to emerge, which can provide guidance for promoting the formation of protective scales on multiphase alloys and for taking advantage of some unique mechanisms that are operative in multiphase alloys but not in single-phase alloys.

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Section: Oxidation Of Two-phase Alloysmentioning

confidence: 99%

Alloy design strategies for promoting protective oxide-scale formation

Brady

Wright

Gleeson

2000

JOM

194

105

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“…The oxidation resistance of NiAI alloys is due to the easy formation and slow growth rate of protective Al 2O3 scales. At low temperatures, y-Al 2O3 is the commonly observed oxide (Doychak, Smialek, and Mitchell 1989;Brumm and Grabke 1992). At temperatures near 1200 K, O-Al 2O3 appears to be the predominant oxide in mature scales, but at higher temperatures, a-Al 2O3 is formed (Rybicki and Smialek 1989).…”

Section: Environmental Resistancementioning

confidence: 99%

“…When Ni-AI was macroalloyed with Cr in sufficient quantity to form MCrAI-based alloys in the y + y'+ a phase field, hot corrosion resistance was very good (Kaufman 1969;Godlewski et al 1989). However, Cr additions adversely affected the cyclic oxidation performance of NiAl alloys in air (Smeggil 1991;Grabke, Brumm, and Steinhorst 1992).…”

Section: Environmental Resistancementioning

confidence: 99%

The Physical and Mechanical Metallurgy of NiAl

Noebe¹,

Bowman²,

Nathal³

1996

Physical Metallurgy and Processing of Intermetallic Compounds

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“…The oxidation of pure metals and single-phase alloys is extensively studied [15][16][17][18], whereas, when the role of constituent phases is concerned, the studies of the oxidation of multiphase alloys are limited [19][20][21]. The oxidation resistance of multiphase alloys can be better, worse or between to that of their constituent phases [17,[21][22][23][24] and main factors that affect the oxidation behavior were shown to be composition and microstructural characteristics of present phases [21,23,25].…”

Section: Introductionmentioning

confidence: 99%