Oxidation behaviour of the Mo–Si–B and Mo–Si–B–Al alloys in the temperature range of 700–1300°C

Paswan, Sharma; Mitra, Rahul; Roy, Sunanda

doi:10.1016/j.intermet.2007.02.012

Cited by 81 publications

(56 citation statements)

References 43 publications

(42 reference statements)

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“…The mechanism of oxide growth is very complex depending on the alloy composition, time and temperature of exposure [13][14][15]. In the present study, the results indicated that the reaction mechanisms of T-800 at various oxidized temperatures were quite different.…”

Section: Discussionmentioning

confidence: 60%

Oxidation Behavior of Tribaloy T-800 Alloy at 800 and 1,000 °C

et al. 2008

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The oxidation behavior of Co-based Tribaloy T-800 alloy has been studied isothermally in air at 800 and 1,000°C, respectively. The results showed that the oxidation mechanism was dependent on the exposure temperature. The oxidation of the alloy followed subparabolic oxidation kinetics at 800°C. The oxide scale at this temperature exhibited a multi-layered structure including an outer layer of Co oxide, a layer composed of complex oxide and spinel, a nonuniform Mo-rich oxide layer, an intermediate mixed oxides layer and an internal attacked layer with different protrusions into Laves phase. During 1,000°C exposure, it followed linear kinetics. The oxidation rendered a relatively uniform external Cr-rich oxide layer coupled with a thin layer of spinel on the top surface and voids at local scale/alloy interface and intergranular region together with internal Si oxide at 1,000°C.

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Section: Discussionmentioning

confidence: 60%

Oxidation Behavior of Tribaloy T-800 Alloy at 800 and 1,000 °C

et al. 2008

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“…Classical alloying approaches regarding Mo-Si-B alloys are adding Cr and/or Al to form protective Cr-and/or Al-oxides. Formation of Al 2 O 3 through alloying with Al seems promising as well as the formation of Cr-oxide which was shown for single phase Mo 3 Si alloyed with Cr [3,4]. For Mo-Si-B alloys, the idea of adding Cr is to protect the alloy up to 900°C through the formation of a Cr-oxide scale and protection through silica takes over for higher temperatures.…”

Section: Introductionmentioning

confidence: 99%

High-Temperature Oxidation Performance of Mo-Si-B Alloys: Current Results, Developments and Opportunities

Burk

Christ

2011

AMR

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Abstract. Ni-base superalloys are approaching the melting point as their fundamental limitation. For high-temperature components one possibility aiming at a further increase of efficiency, e.g. of jet turbines, is the use of refractory metals. Mo as base material is suitable for operating temperatures far beyond 1200°C. As a consequence of the formation of volatile Mo-oxides, it exhibits no intrinsic oxidation resistance when exceeding 700°C. Mo-Si-B alloys have melting points around 2000°C and retain good mechanical properties and oxidation resistance at very high temperatures. In air, the three-phase Mo-Si-B alloy dealt with in this paper shows excellent oxidation behaviour between 900°C-1300°C as a consequence of the formation of a protective silica scale. Below 900°C, alloys of this class suffer from catastrophic oxidation, leading to an evaporation of Mo-oxide and giving rise to a linear rate law of the weight loss. A protective oxide layer is not formed as a consequence of simultaneous and competitive Mo-and Si-oxide formation. Several approaches are possible to improve the oxidation performance of Mo-Si-B alloys, especially in this moderate temperature range. These include classical alloying, e.g. with Cr aiming for protective Cr-oxide scales, addition of small amounts of reactive elements for microstructurerefinement as well as selective oxidation of silica in oxygen-deficient atmospheres prior to operation in air. The results presented show promising opportunities and indicate that an oxidation protection from room temperature up to 1300°C requires a combination of the suggested approaches.

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“…using Cr, Al and Ti [10][11][12], have already been accomplished. Zr is a promising alloying element for grain boundary refinement, which has an effect on mechanical properties, such as improved strength and ductility of the alloy acting in a similar manner as earlier observed for Al-and Mg-based alloys [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Effect of Zr Addition on the High-Temperature Oxidation Behaviour of Mo–Si–B Alloys

et al. 2009

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Mo-Si-B alloys are promising candidates for structural high-temperature applications due to their excellent high-temperature mechanical properties along with high melting temperatures and oxidation resistance. After an initial period with high weight loss rates as a consequence of the volatilization of Mo-oxide, a protective borosilica (glass) layer develops on the alloy surface and steady-state oxidation is achieved. Aiming at improved mechanical properties of Mo-Si-B alloys which exhibit a continuous Mo solid solution matrix as a consequence of a powder metallurgical production route, small amounts of Zr were added. The presence of oxygen in the alloy leads to the formation of thermodynamically very stable Zr-oxide precipitates in the bulk alloy causing an enhancement of its mechanical properties. It was observed that the addition of Zr (distributed in the alloy matrix) also has significant influence on the oxidation behaviour of Mo-Si-B alloys by reducing the period for the formation of the protective and stable silica scale. Furthermore, the weight loss due to vaporization of Mo-oxides is consequently reduced. Besides this beneficial effect, Zr is harmful for the oxidation resistance at temperatures beyond 1,200°C. This is mainly due to the increased oxygen transport through defects in the silica scale.

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Oxidation behaviour of the Mo–Si–B and Mo–Si–B–Al alloys in the temperature range of 700–1300°C

Cited by 81 publications

References 43 publications

Oxidation Behavior of Tribaloy T-800 Alloy at 800 and 1,000 °C

Oxidation Behavior of Tribaloy T-800 Alloy at 800 and 1,000 °C

High-Temperature Oxidation Performance of Mo-Si-B Alloys: Current Results, Developments and Opportunities

Effect of Zr Addition on the High-Temperature Oxidation Behaviour of Mo–Si–B Alloys

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