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P. A. Withey - One of the best experts on this subject based on the ideXlab platform.
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The Influence of ZrO2 Concentration in an Yttria-Based Face Coat for Investment Casting a Ti-45Al-2Mn-2Nb-0.2TiB Alloy Using a Sessile Drop Method
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2015Co-Authors: Xu Cheng, C Yuan, Stuart Blackburn, P. A. WitheyAbstract:Investment casting is widely used to cast near-net shape components, reducing material waste and process cost. Due to the high reactivity of titanium and its alloys, in order to reduce the interaction between the mold and molten titanium, very costly materials are used in the mold face coat. In order to reduce the material cost while maintaining the Chemical Inertness of the face coat, ZrO2 was added into an yttria-based face coat in different concentrations in this study. The face coat properties of the different systems were analyzed using dilatometry and XRD. The Chemical Inertness of the different face coat systems were tested using a sessile drop test using a Ti-45Al-2Mn-2Nb-0.2TiB alloy, and the interactions between the face coat and the alloy were analyzed by the interfacial microstructures, contact angle, and hardness changes. The results showed that small amounts of ZrO2 can be added into yttria without changing the Chemical Inertness of the face coat. High amounts of ZrO2 in the face coat can interact with TiAl alloy to form different interaction products. Meanwhile, both Y2O3 and ZrO2 filler materials were observed to dissolve in molten TiAl during the sessile drop test.
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a comparison of the Chemical Inertness of two y2o3 al2o3 zro2 and y2o3 al2o3 face coat materials through sessile drop and investment casting methods
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2014Co-Authors: P. A. Withey, C Yuan, S. Blackburn, Xu ChengAbstract:Investment casting is uniquely suited to the manufacture of Ti alloys for the production of near net-shape components, reducing material waste, and machining costs. Because of the high reactivity of titanium and its based alloy, the molds which are used in the investment casting process require high Chemical Inertness, which results in them being very costly and non-recyclable. In order to reduce the cost of these molds, traditionally using yttria as the face coat, two alternative molds are developed in this study with face coat materials of Y2O3-Al2O3 and Y2O3-Al2O3-ZrO2. The slurry properties and Chemical Inertness of the face coats were evaluated for viscosity, thermal expansion, friability, and phase development. The Chemical Inertness of these two molds were determined using both the sessile drop test and investment casting to identify the levels of interaction with a Ti-45Al-2Mn-2Nb-0.2B alloy. The results illustrated that the molds using Y2O3-Al2O3 and Y2O3-Al2O3-ZrO2 as the face coats both showed excellent sintering properties and Chemical Inertness when compared to the yttria face coat. They can consequently be used as two alternative face coats for the investment casting of TiAl alloys.
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The study of the influence of binder systems in an Y 2 O 3 -ZrO 2 facecoat material on the investment casting slurries and shells properties
Journal of the European Ceramic Society, 2014Co-Authors: X Cheng, C Yuan, S. Blackburn, P. A. WitheyAbstract:In order to reduce the interaction between the Ti alloys and ceramic shell during the casting, materials with high thermal and Chemical Inertness were used in investment casting. An investigation was undertaken to analyze the influence of the change of binder systems on the slurries, facecoats and the thermo-Chemical properties of the facecoat systems using an Y 2 O 3 -ZrO 2 filler material. The results showed that, using alumina-sol as the binder in the slurry gave the longest life of around three days followed by that using the commercially available zirconia-sol at around 6h, and the yttria sol based slurry giving a shortest life of around 1.5h. Meanwhile using the alumina-sol can also enhance the facecoat sintering properties. There was no obvious evidence observed that the change of the binder system influenced the facecoat Chemical Inertness. © 2014 Elsevier Ltd.
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Influence of Al2O3 concentration in yttria based face coats for investment casting Ti–45Al–2Mn–2Nb–0·2TiB alloy
Materials Science and Technology, 2013Co-Authors: Xu Cheng, C Yuan, Stuart Blackburn, P. A. WitheyAbstract:AbstractAn Al2O3–Y2O3 based face coat material was researched by adding Al2O3 into yttria in different concentrations to reduce the mould cost whilst retaining the face coat Chemical Inertness. The face coat compositions and sintering properties at different temperatures were investigated using X-ray diffraction, friability and dilatometers. Meanwhile, the Chemical Inertness of the face coats was identified using a sessile drop test method to interact with a Ti–45Al–2Mn–2Nb–0·2TiB alloy. The results show that at different firing temperatures, a series of phase transformations have taken place between Y2O3 and Al2O3, resulting in different face coat compositions and sintering properties. However, the Chemical Inertness of the face coat against the molten TiAl alloy was not influenced by the phase transformations, and it was dependent on the amount of Al2O3 added to the face coat. In this experiment, no interaction was observed between the Al2O3–Y2O3 face coat material and TiAl alloy when Al2O3 additions we...
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Evaluation of the Inertness of Investment Casting Molds Using Both Sessile Drop and Centrifugal Casting Methods
Metallurgical and Materials Transactions A, 2013Co-Authors: Xu Cheng, Chen Yuan, Nick Green, P. A. WitheyAbstract:The investment casting process is an economic production method for engineering components in TiAl-based alloys and offers the benefits of a near net-shaped component with a good surface finish. An investigation was undertaken to develop three new face coat systems based on yttria, but with better sintering properties. These face coat systems were mainly based on an yttria-alumina-zirconia system (Y_2O_3-0.5 wt pct Al_2O_3-0.5 wt pct ZrO_2), an yttria-fluoride system (Y_2O_3-0.15 wt pct YF_3), and an yttria-boride system (Y_2O_3-0.15 wt pct B_2O_3). After sintering, the Chemical Inertness of the face coat was first tested and analyzed using a sessile drop test through the metal wetting behavioral change for each face coat surface. Then, the interactions between the shell and metal were studied by centrifugal investment casting TiAl bars. Although the sintering aids in yttria can decrease the Chemical Inertness of the face coat, the thickness of the interaction layer in the casting was less than 10 μ m; therefore, these face coats still can be possible face coat materials for investment casting TiAl alloys.
Xu Cheng - One of the best experts on this subject based on the ideXlab platform.
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The Influence of ZrO2 Concentration in an Yttria-Based Face Coat for Investment Casting a Ti-45Al-2Mn-2Nb-0.2TiB Alloy Using a Sessile Drop Method
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2015Co-Authors: Xu Cheng, C Yuan, Stuart Blackburn, P. A. WitheyAbstract:Investment casting is widely used to cast near-net shape components, reducing material waste and process cost. Due to the high reactivity of titanium and its alloys, in order to reduce the interaction between the mold and molten titanium, very costly materials are used in the mold face coat. In order to reduce the material cost while maintaining the Chemical Inertness of the face coat, ZrO2 was added into an yttria-based face coat in different concentrations in this study. The face coat properties of the different systems were analyzed using dilatometry and XRD. The Chemical Inertness of the different face coat systems were tested using a sessile drop test using a Ti-45Al-2Mn-2Nb-0.2TiB alloy, and the interactions between the face coat and the alloy were analyzed by the interfacial microstructures, contact angle, and hardness changes. The results showed that small amounts of ZrO2 can be added into yttria without changing the Chemical Inertness of the face coat. High amounts of ZrO2 in the face coat can interact with TiAl alloy to form different interaction products. Meanwhile, both Y2O3 and ZrO2 filler materials were observed to dissolve in molten TiAl during the sessile drop test.
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a comparison of the Chemical Inertness of two y2o3 al2o3 zro2 and y2o3 al2o3 face coat materials through sessile drop and investment casting methods
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2014Co-Authors: P. A. Withey, C Yuan, S. Blackburn, Xu ChengAbstract:Investment casting is uniquely suited to the manufacture of Ti alloys for the production of near net-shape components, reducing material waste, and machining costs. Because of the high reactivity of titanium and its based alloy, the molds which are used in the investment casting process require high Chemical Inertness, which results in them being very costly and non-recyclable. In order to reduce the cost of these molds, traditionally using yttria as the face coat, two alternative molds are developed in this study with face coat materials of Y2O3-Al2O3 and Y2O3-Al2O3-ZrO2. The slurry properties and Chemical Inertness of the face coats were evaluated for viscosity, thermal expansion, friability, and phase development. The Chemical Inertness of these two molds were determined using both the sessile drop test and investment casting to identify the levels of interaction with a Ti-45Al-2Mn-2Nb-0.2B alloy. The results illustrated that the molds using Y2O3-Al2O3 and Y2O3-Al2O3-ZrO2 as the face coats both showed excellent sintering properties and Chemical Inertness when compared to the yttria face coat. They can consequently be used as two alternative face coats for the investment casting of TiAl alloys.
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Influence of Al2O3 concentration in yttria based face coats for investment casting Ti–45Al–2Mn–2Nb–0·2TiB alloy
Materials Science and Technology, 2013Co-Authors: Xu Cheng, C Yuan, Stuart Blackburn, P. A. WitheyAbstract:AbstractAn Al2O3–Y2O3 based face coat material was researched by adding Al2O3 into yttria in different concentrations to reduce the mould cost whilst retaining the face coat Chemical Inertness. The face coat compositions and sintering properties at different temperatures were investigated using X-ray diffraction, friability and dilatometers. Meanwhile, the Chemical Inertness of the face coats was identified using a sessile drop test method to interact with a Ti–45Al–2Mn–2Nb–0·2TiB alloy. The results show that at different firing temperatures, a series of phase transformations have taken place between Y2O3 and Al2O3, resulting in different face coat compositions and sintering properties. However, the Chemical Inertness of the face coat against the molten TiAl alloy was not influenced by the phase transformations, and it was dependent on the amount of Al2O3 added to the face coat. In this experiment, no interaction was observed between the Al2O3–Y2O3 face coat material and TiAl alloy when Al2O3 additions we...
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Evaluation of the Inertness of Investment Casting Molds Using Both Sessile Drop and Centrifugal Casting Methods
Metallurgical and Materials Transactions A, 2013Co-Authors: Xu Cheng, Chen Yuan, Nick Green, P. A. WitheyAbstract:The investment casting process is an economic production method for engineering components in TiAl-based alloys and offers the benefits of a near net-shaped component with a good surface finish. An investigation was undertaken to develop three new face coat systems based on yttria, but with better sintering properties. These face coat systems were mainly based on an yttria-alumina-zirconia system (Y_2O_3-0.5 wt pct Al_2O_3-0.5 wt pct ZrO_2), an yttria-fluoride system (Y_2O_3-0.15 wt pct YF_3), and an yttria-boride system (Y_2O_3-0.15 wt pct B_2O_3). After sintering, the Chemical Inertness of the face coat was first tested and analyzed using a sessile drop test through the metal wetting behavioral change for each face coat surface. Then, the interactions between the shell and metal were studied by centrifugal investment casting TiAl bars. Although the sintering aids in yttria can decrease the Chemical Inertness of the face coat, the thickness of the interaction layer in the casting was less than 10 μ m; therefore, these face coats still can be possible face coat materials for investment casting TiAl alloys.
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an investigation of a tialo based refractory slurry face coat system for the investment casting of ti al alloys
Intermetallics, 2012Co-Authors: Xu Cheng, P. A. Withey, C Yuan, N R GreenAbstract:Abstract The investment casting process offers great freedom of design with the economic advantage of near net shape production and has been widely used to process TiAl alloys. An investigation was undertaken to develop stable and cheap refractory slurry systems, suitable for use as a face coat in the investment casting of titanium aluminides. A TiO2–Al2O3 (TiAlO) based face coat slurry was investigated and compared with a traditional yttria based face coat slurry. After sintering, the Chemical Inertness of the manufactured shells in contact with molten TiAl alloys was tested by simulating the casting process using a flash re-melting test, in which sample shells were in contact with titanium aluminides at given temperatures for varying time durations and subsequently re-solidified. Compared with yttria, the TiAlO face coat had relatively lower Chemical Inertness against molten alloys, forming a thick hardened layer at the metal/shell interface with massive interaction products along grain boundaries. The reaction also changed the wetting behaviour of the TiAl on the TiAlO face coat with the contact angle decreasing as a function of interaction time.
Yung I. Chen - One of the best experts on this subject based on the ideXlab platform.
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bonding characteristics and Chemical Inertness of zr si n coatings with a high si content in glass molding
THE Coatings, 2018Co-Authors: Li-chun Chang, Yung I. Chen, Yuzhe Zheng, Shanchun ChangAbstract:High-Si-content transition metal nitride coatings, which exhibited an X-ray amorphous phase, were proposed as protective coatings on glass molding dies. In a previous study, the Zr–Si–N coatings with Si contents of 24–30 at.% exhibited the hardness of Si3N4, which was higher than those of the middle-Si-content (19 at.%) coatings. In this study, the bonding characteristics of the constituent elements of Zr–Si–N coatings were evaluated through X-ray photoelectron spectroscopy. Results indicated that the Zr 3d5/2 levels were 179.14–180.22 and 180.75–181.61 eV for the Zr–N bonds in ZrN and Zr3N4 compounds, respectively. Moreover, the percentage of Zr–N bond in the Zr3N4 compound increased with increasing Si content in the Zr–Si–N coatings. The Zr–N bond of Zr3N4 dominated when the Si content was >24 at.%. Therefore, high Si content can stabilize the Zr–N compound in the M3N4 bonding structure. Furthermore, the thermal stability and Chemical Inertness of Zr–Si–N coatings were evaluated by conducting thermal cycle annealing at 270 °C and 600 °C in a 15-ppm O2–N2 atmosphere. The results indicated that a Zr22Si29N49/Ti/WC assembly was suitable as a protective coating against SiO2–B2O3–BaO-based glass for 450 thermal cycles.
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Chemical Inertness of ta si n coatings in glass molding
Thin Solid Films, 2015Co-Authors: Yung I. Chen, Yu Ru Cheng, Li-chun Chang, Tso Shen LuAbstract:Abstract Cr–W–N coatings with a Cr interlayer were prepared using reactive direct-current magnetron cosputtering on Si and cemented carbide substrates. To investigate the Chemical Inertness of Cr–W–N coatings against commercial moldable SiO2–B2O3–BaO-based glass in glass molding, thermal cycle annealing at 270 °C and 600 °C was performed in a quartz tube furnace in a 15-ppm O2–N2 atmosphere. Variations in the crystalline structure, mechanical properties, and surface roughness after various annealing durations were investigated. The results indicated that Cr37W31N32 and Cr24W46N30 coatings maintained a face-centered cubic phase and exhibited superior mechanical properties and low surface roughness after up to 1000 thermal cycles; these properties were attributed to the formation of amorphous oxide scales. By contrast, Cr8W69N23 and Cr4W82N14 coatings with a nanocrystalline W phase in the as-deposited state formed WO3 oxide scales after annealing, which negatively affected their mechanical properties and raised surface roughness values.
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Chemical Inertness of Ta-Si-N coatings in glass molding
Thin Solid Films, 2015Co-Authors: Yung I. Chen, Yu Ru Cheng, Li-chun Chang, Tso Shen LuAbstract:Glass molding can be employed to fabricate high-quality lenses with a lower cost and higher process rate than those of the traditional glass lens production method. Glass molding is widely employed in manufacturing precision optical elements with aspheric surfaces. In this study, amorphous Ta-Si-N coatings with a Ti interlayer were sputtered on cemented carbide substrates to evaluate their potential as protective coatings on glass molding dies. Commercial moldable SiO2-B2O3-BaO-based and B2O3-ZnO-La2O3-based glasses were used to evaluate the Chemical Inertness of Ta-Si-N coatings in glass molding. Thermal cycle annealing, which involves annealing at 270°C and 600°C and maintaining the glasses at 600°C ± 10°C for 1 min/cycle, was conducted in a quartz tube furnace to simulate glass molding in a continuous flow of a 15-ppm O2-N2 atmosphere. The glass and coating assemblies were subjected to up to 1000 thermal cycles. The variations in the crystalline structure and surface roughness after various annealing durations were investigated.
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the Chemical Inertness of ir re and ta ru coatings in molding b2o3 zno la2o3 based glass
Surface & Coatings Technology, 2014Co-Authors: Yung I. Chen, Jiinjyh Shyu, Hungyin Tsai, Yunghsing ChenAbstract:Abstract B 2 O 3 –ZnO–La 2 O 3 -based glasses with a high refractive index are widely used as optical glass materials for lenses. To evaluate the feasibility of applying protective coatings on glass molding dies, Ir–Re and Ta–Ru coatings were sputtered on cemented tungsten carbide or silicon substrates. B 2 O 3 –ZnO–La 2 O 3 -based glasses were placed on the surface of the coatings and heat-treated in a glass molding atmosphere of 15-ppm O 2 –N 2 at a molding temperature of 600 °C. Up to 1000 thermal cycling annealing tests were performed at 270 °C and 600 °C. The holding time at the molding temperature was set at 1 min for each cycle. The variations in Chemical Inertness, residual stress, and coating characteristics after annealing were investigated.
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The Chemical Inertness of Ir–Re and Ta–Ru coatings in molding B2O3–ZnO–La2O3-based glass
Surface & Coatings Technology, 2014Co-Authors: Yung I. Chen, Jiinjyh Shyu, Hungyin Tsai, Yunghsing ChenAbstract:Abstract B 2 O 3 –ZnO–La 2 O 3 -based glasses with a high refractive index are widely used as optical glass materials for lenses. To evaluate the feasibility of applying protective coatings on glass molding dies, Ir–Re and Ta–Ru coatings were sputtered on cemented tungsten carbide or silicon substrates. B 2 O 3 –ZnO–La 2 O 3 -based glasses were placed on the surface of the coatings and heat-treated in a glass molding atmosphere of 15-ppm O 2 –N 2 at a molding temperature of 600 °C. Up to 1000 thermal cycling annealing tests were performed at 270 °C and 600 °C. The holding time at the molding temperature was set at 1 min for each cycle. The variations in Chemical Inertness, residual stress, and coating characteristics after annealing were investigated.
Yunghsing Chen - One of the best experts on this subject based on the ideXlab platform.
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the Chemical Inertness of ir re and ta ru coatings in molding b2o3 zno la2o3 based glass
Surface & Coatings Technology, 2014Co-Authors: Yung I. Chen, Jiinjyh Shyu, Hungyin Tsai, Yunghsing ChenAbstract:Abstract B 2 O 3 –ZnO–La 2 O 3 -based glasses with a high refractive index are widely used as optical glass materials for lenses. To evaluate the feasibility of applying protective coatings on glass molding dies, Ir–Re and Ta–Ru coatings were sputtered on cemented tungsten carbide or silicon substrates. B 2 O 3 –ZnO–La 2 O 3 -based glasses were placed on the surface of the coatings and heat-treated in a glass molding atmosphere of 15-ppm O 2 –N 2 at a molding temperature of 600 °C. Up to 1000 thermal cycling annealing tests were performed at 270 °C and 600 °C. The holding time at the molding temperature was set at 1 min for each cycle. The variations in Chemical Inertness, residual stress, and coating characteristics after annealing were investigated.
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The Chemical Inertness of Ir–Re and Ta–Ru coatings in molding B2O3–ZnO–La2O3-based glass
Surface & Coatings Technology, 2014Co-Authors: Yung I. Chen, Jiinjyh Shyu, Hungyin Tsai, Yunghsing ChenAbstract:Abstract B 2 O 3 –ZnO–La 2 O 3 -based glasses with a high refractive index are widely used as optical glass materials for lenses. To evaluate the feasibility of applying protective coatings on glass molding dies, Ir–Re and Ta–Ru coatings were sputtered on cemented tungsten carbide or silicon substrates. B 2 O 3 –ZnO–La 2 O 3 -based glasses were placed on the surface of the coatings and heat-treated in a glass molding atmosphere of 15-ppm O 2 –N 2 at a molding temperature of 600 °C. Up to 1000 thermal cycling annealing tests were performed at 270 °C and 600 °C. The holding time at the molding temperature was set at 1 min for each cycle. The variations in Chemical Inertness, residual stress, and coating characteristics after annealing were investigated.
C Yuan - One of the best experts on this subject based on the ideXlab platform.
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The Influence of ZrO2 Concentration in an Yttria-Based Face Coat for Investment Casting a Ti-45Al-2Mn-2Nb-0.2TiB Alloy Using a Sessile Drop Method
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2015Co-Authors: Xu Cheng, C Yuan, Stuart Blackburn, P. A. WitheyAbstract:Investment casting is widely used to cast near-net shape components, reducing material waste and process cost. Due to the high reactivity of titanium and its alloys, in order to reduce the interaction between the mold and molten titanium, very costly materials are used in the mold face coat. In order to reduce the material cost while maintaining the Chemical Inertness of the face coat, ZrO2 was added into an yttria-based face coat in different concentrations in this study. The face coat properties of the different systems were analyzed using dilatometry and XRD. The Chemical Inertness of the different face coat systems were tested using a sessile drop test using a Ti-45Al-2Mn-2Nb-0.2TiB alloy, and the interactions between the face coat and the alloy were analyzed by the interfacial microstructures, contact angle, and hardness changes. The results showed that small amounts of ZrO2 can be added into yttria without changing the Chemical Inertness of the face coat. High amounts of ZrO2 in the face coat can interact with TiAl alloy to form different interaction products. Meanwhile, both Y2O3 and ZrO2 filler materials were observed to dissolve in molten TiAl during the sessile drop test.
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a comparison of the Chemical Inertness of two y2o3 al2o3 zro2 and y2o3 al2o3 face coat materials through sessile drop and investment casting methods
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2014Co-Authors: P. A. Withey, C Yuan, S. Blackburn, Xu ChengAbstract:Investment casting is uniquely suited to the manufacture of Ti alloys for the production of near net-shape components, reducing material waste, and machining costs. Because of the high reactivity of titanium and its based alloy, the molds which are used in the investment casting process require high Chemical Inertness, which results in them being very costly and non-recyclable. In order to reduce the cost of these molds, traditionally using yttria as the face coat, two alternative molds are developed in this study with face coat materials of Y2O3-Al2O3 and Y2O3-Al2O3-ZrO2. The slurry properties and Chemical Inertness of the face coats were evaluated for viscosity, thermal expansion, friability, and phase development. The Chemical Inertness of these two molds were determined using both the sessile drop test and investment casting to identify the levels of interaction with a Ti-45Al-2Mn-2Nb-0.2B alloy. The results illustrated that the molds using Y2O3-Al2O3 and Y2O3-Al2O3-ZrO2 as the face coats both showed excellent sintering properties and Chemical Inertness when compared to the yttria face coat. They can consequently be used as two alternative face coats for the investment casting of TiAl alloys.
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The study of the influence of binder systems in an Y 2 O 3 -ZrO 2 facecoat material on the investment casting slurries and shells properties
Journal of the European Ceramic Society, 2014Co-Authors: X Cheng, C Yuan, S. Blackburn, P. A. WitheyAbstract:In order to reduce the interaction between the Ti alloys and ceramic shell during the casting, materials with high thermal and Chemical Inertness were used in investment casting. An investigation was undertaken to analyze the influence of the change of binder systems on the slurries, facecoats and the thermo-Chemical properties of the facecoat systems using an Y 2 O 3 -ZrO 2 filler material. The results showed that, using alumina-sol as the binder in the slurry gave the longest life of around three days followed by that using the commercially available zirconia-sol at around 6h, and the yttria sol based slurry giving a shortest life of around 1.5h. Meanwhile using the alumina-sol can also enhance the facecoat sintering properties. There was no obvious evidence observed that the change of the binder system influenced the facecoat Chemical Inertness. © 2014 Elsevier Ltd.
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Influence of Al2O3 concentration in yttria based face coats for investment casting Ti–45Al–2Mn–2Nb–0·2TiB alloy
Materials Science and Technology, 2013Co-Authors: Xu Cheng, C Yuan, Stuart Blackburn, P. A. WitheyAbstract:AbstractAn Al2O3–Y2O3 based face coat material was researched by adding Al2O3 into yttria in different concentrations to reduce the mould cost whilst retaining the face coat Chemical Inertness. The face coat compositions and sintering properties at different temperatures were investigated using X-ray diffraction, friability and dilatometers. Meanwhile, the Chemical Inertness of the face coats was identified using a sessile drop test method to interact with a Ti–45Al–2Mn–2Nb–0·2TiB alloy. The results show that at different firing temperatures, a series of phase transformations have taken place between Y2O3 and Al2O3, resulting in different face coat compositions and sintering properties. However, the Chemical Inertness of the face coat against the molten TiAl alloy was not influenced by the phase transformations, and it was dependent on the amount of Al2O3 added to the face coat. In this experiment, no interaction was observed between the Al2O3–Y2O3 face coat material and TiAl alloy when Al2O3 additions we...
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an investigation of a tialo based refractory slurry face coat system for the investment casting of ti al alloys
Intermetallics, 2012Co-Authors: Xu Cheng, P. A. Withey, C Yuan, N R GreenAbstract:Abstract The investment casting process offers great freedom of design with the economic advantage of near net shape production and has been widely used to process TiAl alloys. An investigation was undertaken to develop stable and cheap refractory slurry systems, suitable for use as a face coat in the investment casting of titanium aluminides. A TiO2–Al2O3 (TiAlO) based face coat slurry was investigated and compared with a traditional yttria based face coat slurry. After sintering, the Chemical Inertness of the manufactured shells in contact with molten TiAl alloys was tested by simulating the casting process using a flash re-melting test, in which sample shells were in contact with titanium aluminides at given temperatures for varying time durations and subsequently re-solidified. Compared with yttria, the TiAlO face coat had relatively lower Chemical Inertness against molten alloys, forming a thick hardened layer at the metal/shell interface with massive interaction products along grain boundaries. The reaction also changed the wetting behaviour of the TiAl on the TiAlO face coat with the contact angle decreasing as a function of interaction time.