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What type of defects are formed when dislocations glide through g’ precipitates during plastic deformation?
What type of defects are formed when dislocations glide through g’ precipitates during plastic deformation?
What contributes to the high-temperature strength of superalloys according to the text?
What contributes to the high-temperature strength of superalloys according to the text?
In superalloys, what type of strengthening mechanism occurs when precipitates form coherent interfaces with the parent phase?
In superalloys, what type of strengthening mechanism occurs when precipitates form coherent interfaces with the parent phase?
What distinguishes single-crystal turbine blades from polycrystalline turbine discs in superalloy components?
What distinguishes single-crystal turbine blades from polycrystalline turbine discs in superalloy components?
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Which property of the g’ phase in superalloys is responsible for the strength increase with temperature anomaly?
Which property of the g’ phase in superalloys is responsible for the strength increase with temperature anomaly?
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Why must superalloys in harsh environments be adequately protected?
Why must superalloys in harsh environments be adequately protected?
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What is one way to judge whether an oxide will be protective?
What is one way to judge whether an oxide will be protective?
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Which of the following substances has low oxygen diffusivity in its oxide, making it a good candidate for protection?
Which of the following substances has low oxygen diffusivity in its oxide, making it a good candidate for protection?
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What type of coating volatilises at higher temperatures but provides good corrosion resistance?
What type of coating volatilises at higher temperatures but provides good corrosion resistance?
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Which type of turbine blade coating is produced by plasma spraying and has a 'Herring bone' morphology?
Which type of turbine blade coating is produced by plasma spraying and has a 'Herring bone' morphology?
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What caused the failure in the turbine disc mentioned in the text?
What caused the failure in the turbine disc mentioned in the text?
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Which processing route for disc manufacture is more expensive but allows for precise grain size control?
Which processing route for disc manufacture is more expensive but allows for precise grain size control?
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What is the significance of the VIM→ESR→VAR method mentioned in the text?
What is the significance of the VIM→ESR→VAR method mentioned in the text?
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What type of alloys are suitable for the Cast and Wrought processing route?
What type of alloys are suitable for the Cast and Wrought processing route?
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Why is it important that turbine discs are manufactured from high-purity alloys?
Why is it important that turbine discs are manufactured from high-purity alloys?
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What process is used to dissolve all g’ precipitates and homogenize the composition in turbine blades?
What process is used to dissolve all g’ precipitates and homogenize the composition in turbine blades?
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What is the purpose of the primary ageing treatment in the heat treatment of turbine blades?
What is the purpose of the primary ageing treatment in the heat treatment of turbine blades?
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Which of the following casting defects might result in a blade being scrapped according to the text?
Which of the following casting defects might result in a blade being scrapped according to the text?
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What operation involves applying a bond coat to turbine blades?
What operation involves applying a bond coat to turbine blades?
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In the heat treatment process of turbine blades, what temperature is used for the secondary ageing treatment?
In the heat treatment process of turbine blades, what temperature is used for the secondary ageing treatment?
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What is the purpose of the Vacuum Arc Remelting (VAR) process?
What is the purpose of the Vacuum Arc Remelting (VAR) process?
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Why is Vacuum Arc Remelting (VAR) considered a slow and expensive process?
Why is Vacuum Arc Remelting (VAR) considered a slow and expensive process?
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What advantage does Vacuum Arc Remelting (VAR) offer in terms of microstructural control?
What advantage does Vacuum Arc Remelting (VAR) offer in terms of microstructural control?
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Why are some metals processed using Vacuum Arc Remelting (VAR) instead of open air furnaces?
Why are some metals processed using Vacuum Arc Remelting (VAR) instead of open air furnaces?
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What is the purpose of converting ingots into forged billets after the VIM+ESR+VAR stages?
What is the purpose of converting ingots into forged billets after the VIM+ESR+VAR stages?
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Study Notes
- Order strengthening occurs due to the formation of antiphase boundary defects when dislocations glide through g’ precipitates during plastic deformation in superalloys.
- The g’ phase in superalloys is ductile compared to most intermetallics, exhibits a Yield Stress Anomaly where strength increases with temperature, precipitates from the γ phase via short-range ordering, and has a low lattice parameter mismatch forming coherent interfaces with the parent γ phase.
- Superalloys exhibit a combination of beneficial strengthening mechanisms including solution strengthening, order strengthening, precipitate strengthening, and coherency strengthening.
- Superalloy components can be single-crystals (SX) with high volume fraction of g’ suitable for turbine blades, or polycrystalline (PX) with smaller volume fraction of g’ suitable for turbine discs and combustors.
- Turbine blades made of single-crystal superalloys have complex geometries with internal cooling channels while turbine discs are around 20% of engine weight and require high strength but light materials.
- Processing routes for turbine disc manufacture include cast and wrought methods suitable for alloys with lower g’ content, and powder metallurgy method suitable for alloys with higher g’ content allowing precise grain size control.
- To ensure high quality, alloys used for turbine discs are produced using VIM→ESR→VAR method, where Vacuum Induction Melting (VIM) is used to produce primary alloy ingots, Electroslag Remelting (ESR) further purifies the ingots, and Vacuum Arc Remelting (VAR) achieves highest purity for mission-critical applications.
- Post-casting operations for turbine blades include heat treatments like solution treatment and ageing treatments to optimize microstructure, and finishing procedures like applying bond coats, depositing TBCs, laser drilling cooling holes, and undergoing NDT.
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Description
This quiz covers the formation of antiphase boundary defects when dislocations glide through g’ precipitates during plastic deformation in superalloys. It also discusses the special properties of the g’ phase contributing to high-temperature strength, such as ductility and strength increase with temperature.
