WO2017134138A1 - Matériaux céramiques lixiviables pour le moulage - Google Patents

Matériaux céramiques lixiviables pour le moulage Download PDF

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Publication number
WO2017134138A1
WO2017134138A1 PCT/EP2017/052209 EP2017052209W WO2017134138A1 WO 2017134138 A1 WO2017134138 A1 WO 2017134138A1 EP 2017052209 W EP2017052209 W EP 2017052209W WO 2017134138 A1 WO2017134138 A1 WO 2017134138A1
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WO
WIPO (PCT)
Prior art keywords
phase
alumina
matrix
silica
sintered
Prior art date
Application number
PCT/EP2017/052209
Other languages
English (en)
Inventor
Eric Larson
Douglas Mccracken
Original Assignee
Morgan Advanced Ceramics, Inc
Boff, James
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Morgan Advanced Ceramics, Inc, Boff, James filed Critical Morgan Advanced Ceramics, Inc
Priority to GB1800344.2A priority Critical patent/GB2553481A/en
Publication of WO2017134138A1 publication Critical patent/WO2017134138A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes

Definitions

  • This invention relates to leachable ceramic materials and to their use in investment casting.
  • Investment casting is a process in which molten metals are poured into a refractory ceramic mould designed to create a duplicate of the desired part. Casting may be done around "cores". Ceramic materials used for such purposes include chemically bonded particles of materials such as silica, zircon, aluminium silicates (e.g. mullite), and alumina. Such materials are porous with low structural integrity and are simply required to resist the pressures and temperatures implicit in the casting process. After casting these materials are removed to leave the cast product remaining.
  • core materials include those of US4073662, US4187266, US4837187, US5779809, GB1602027, and GB2126569. When making large items by investment casting it is frequently necessary to provide additional support to parts of the mould/core.
  • Such supports it is conventional to use dense ceramics, for example such as quartz and alumina rods.
  • Such rods may be of a variety of sizes, but typically range in diameter from 0.2 to 40mm. The present disclosure is not however limited to such ranges of diameter.
  • Such supports need to be removed after the casting process and it is common to leach out the ceramic.
  • Quartz is the traditional material of choice, since it can be leached out easily using strong aqueous solutions of hydroxides such as NaOH.
  • Alumina is increasingly being used as it has a higher mechanical strength than quartz.
  • alumina is chemically more inert to hydroxides, and typically leach cycle times are increased from one day (for quartz) to three days (for alumina) and requires the more aggressive KOH as a strong aqueous solution.
  • This disclosure provides materials that are mechanically stronger than quartz, and yet chemically weaker than alumina, permitting shorter leach times in aqueous hydroxide solution than normal dense alumina without the strength limitation of quartz.
  • alumina materials comprising:- ⁇ a mechanically supportive continuous matrix phase comprising alumina;
  • the material preferably comprises at least lvol% of the at least one second phase, preferably more than 3vol%, and conveniently can comprise 5 ⁇ 3vol% or 5 ⁇ 2vol% or 5 ⁇ lvol%.
  • the amount of the at least one second phase may be up to 10vol%, 20vol% or more.
  • the present disclosure aims to use the mechanical strength of alumina to provide materials having a greater strength than quartz, but provides a second phase
  • aluminas used as supports in investment casting are dense ceramics comprising very low amounts of other components (typically being 95% or more pure alumina). Typical modulus of rupture for such a material would be of the order of 550 MPa (80kpsi). Dissolution by KOH leachant is by attack at the surface.
  • quartz used as supports in investment casting are glassy materials comprising essentially pure silica. Typical modulus of rupture for such a material would be of the order of 210 MPa (30kpsi). Dissolution by NaOH or KOH leachant is by attack at the surface, and quartz is attacked more vigorously than is alumina.
  • the present disclosure provides an alumina containing matrix (that may incorporate other materials) and at least one second phase that interpenetrates the matrix and that provides a pathway for leachants.
  • the second phase may comprise porosity (that enables penetration of the leachants below the surface); and may comprise a leachable phase that is more readily leachable than the matrix, so that preferential leaching of the leachable phase permits leachant to penetrate below the surface.
  • the effect is to increase the area of the matrix phase that is exposed to the leachant above that of the outer surface of the support. This increased leachant contact permits quicker leaching of the material of the matrix.
  • this invention contemplates materials having modulus of rupture above 250 MPa, above 300 MPa, and above 350 MPa.
  • Example 1 porosity as second phase
  • a 99.8% pure alumina powder [Grade 998E powder from Morgan Advanced Materials (from their Latrobe facility); a sub-micron powder with a d50 less than one micron] was pressed or extruded to form rods and other shapes which were fired at 1350°C with a ramp time 2.5 hours to 1350°C, soak for 1.5 to 2 hours , ramp down time of 0.5 to 1.5 hours with a total cycle time of 5-6 hours to provide porous sintered alumina shapes, including cylindrical rods having a cross section ranging from ⁇ 0.25mm to ⁇ 40mm (0.010" to 1.6"), and having a porosity in the range 5-7%.
  • Example 2 - leachable material as second phase A 99.8% alumina powder [Grade 998E powder from Morgan Advanced Materials (from their Latrobe facility); a sub-micron powder with a d50 less than one micron] was mixed with sub-micron silica [Grade GP3i from Harbison Walker] in proportions to create a 97% alumina containing mixture.
  • the mixture was pressed or extruded to form rods and other shapes which were fired at 1650°C with a ramp time of 14 hours to 1650°C, soak for 2 hours , ramp down time of 8 hours for a total cycle time of 24 hours to provide fully sintered alumino-silicate cylindrical shapes, including rods having a cross section ranging from ⁇ 0.25mm to ⁇ 40mm (0.010" to 1.6").
  • Example 3 leachable material as second phase
  • a 99.8% alumina powder [Grade 998E powder from Morgan Advanced Materials (from their Latrobe facility); a sub-micron powder with a d50 less than one micron] was mixed with sub-micron silica [Grade GP3i from Harbison Walker] in proportions to create a 95% alumina containing mixture.
  • the mixture was pressed or extruded to form rods and other shapes which were fired at 1650°C with a ramp time of 14 hours to 1650°C, soak for 2 hours , ramp down time of 8 hours for a total cycle time of 24 hours to provide fully sintered alumino-silicate cylindrical shapes, including rods having a cross section ranging from ⁇ 0.25mm to ⁇ 40mm (0.010" to 1.6").
  • Modulus of rupture of the rods of examples 1 to 3 were measured using a 3-point method [ASTM D790].
  • the samples measured were ⁇ 35mm (1 3 ⁇ 4") sections cut from 0.79mm (0.031") diameter circular cross-section rods of material.
  • silica used in manufacture of alumino-silicates in accordance with this invention should be fine materials to avoid excessive weakening of the structure of the support material.
  • silicas with a d50 ⁇ l ⁇ m are used and good results may be achieved with d50 in the range 0.5 ⁇ 0.2 ⁇ or d50 in the range 0.5 ⁇ 0.1 ⁇ .
  • the present invention is not limited to these particular ranges however.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Compositions Of Oxide Ceramics (AREA)
  • Mold Materials And Core Materials (AREA)

Abstract

L'invention concerne un procédé pour supporter des parties de moule et/ou des noyaux lors d'un processus de moulage de précision, consistant à utiliser des supports comprenant un matériau support contenant une phase de matrice continue à soutien mécanique comprenant de l'alumine ; et au moins une deuxième phase interpénétrant la phase de matrice et permettant aux agents lixiviants de pénétrer dans le matériau.
PCT/EP2017/052209 2016-02-05 2017-02-02 Matériaux céramiques lixiviables pour le moulage WO2017134138A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB1800344.2A GB2553481A (en) 2016-02-05 2017-02-02 Leachable ceramic materials for use in casting

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US201662291858P 2016-02-05 2016-02-05
US62/291,858 2016-02-05

Publications (1)

Publication Number Publication Date
WO2017134138A1 true WO2017134138A1 (fr) 2017-08-10

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2017/052209 WO2017134138A1 (fr) 2016-02-05 2017-02-02 Matériaux céramiques lixiviables pour le moulage

Country Status (2)

Country Link
GB (1) GB2553481A (fr)
WO (1) WO2017134138A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019030025A1 (fr) 2017-08-08 2019-02-14 Morgan Advanced Ceramics, Inc Matériaux céramiques se prêtant à la lixiviation pour le moulage

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4073662A (en) 1977-03-09 1978-02-14 General Electric Company Method for removing a magnesia doped alumina core material
US4187266A (en) 1977-10-06 1980-02-05 General Electric Company Process for making a ceramic article having a dense integral outer barrier layer and a high degree of porosity and crushability characteristics
US4221594A (en) * 1977-10-06 1980-09-09 General Electric Company Material composition for fired ceramic articles having a high degree of porosity and crushability characteristics
GB1602027A (en) 1977-10-06 1981-11-04 Gen Electric Method for removing cores
GB2126569A (en) 1982-09-04 1984-03-28 Rolls Royce Non-silica based ceramic cores for castings
US4837187A (en) 1987-06-04 1989-06-06 Howmet Corporation Alumina-based core containing yttria
EP0539317A1 (fr) * 1991-09-20 1993-04-28 United Technologies Corporation Procédé pour la fabrication de noyaux pour le moulage de précision
US5779809A (en) 1995-12-26 1998-07-14 General Electric Company Method of dissolving or leaching ceramic cores in airfoils

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4073662A (en) 1977-03-09 1978-02-14 General Electric Company Method for removing a magnesia doped alumina core material
US4187266A (en) 1977-10-06 1980-02-05 General Electric Company Process for making a ceramic article having a dense integral outer barrier layer and a high degree of porosity and crushability characteristics
US4221594A (en) * 1977-10-06 1980-09-09 General Electric Company Material composition for fired ceramic articles having a high degree of porosity and crushability characteristics
GB1602027A (en) 1977-10-06 1981-11-04 Gen Electric Method for removing cores
GB2126569A (en) 1982-09-04 1984-03-28 Rolls Royce Non-silica based ceramic cores for castings
US4837187A (en) 1987-06-04 1989-06-06 Howmet Corporation Alumina-based core containing yttria
EP0539317A1 (fr) * 1991-09-20 1993-04-28 United Technologies Corporation Procédé pour la fabrication de noyaux pour le moulage de précision
US5779809A (en) 1995-12-26 1998-07-14 General Electric Company Method of dissolving or leaching ceramic cores in airfoils

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
ANONYMOUS: "Micro particles based on silicon dioxide size: 0.5 [mu]m | Sigma-Aldrich", 17 March 2017 (2017-03-17), XP055356664, Retrieved from the Internet <URL:http://www.sigmaaldrich.com/catalog/product/sigma/56796?lang=en ion=NL> [retrieved on 20170320] *
LI GE WANG ET AL: "Effect of SiO<sub>2</sub> Micro-Powders on the Properties of Alumina-Based Ceramic Core", ADVANCED MATERIALS RESEARCH, vol. 554-556, 1 January 2012 (2012-01-01), pages 731 - 735, XP055356525, DOI: 10.4028/www.scientific.net/AMR.554-556.731 *
QIN Y ET AL: "Effect of silica sol on the properties of alumina-based ceramic core composites", MATERIALS SCIENCE AND ENGINEERING: A, ELSEVIER, AMSTERDAM, NL, vol. 508, no. 1-2, 20 May 2009 (2009-05-20), pages 71 - 75, XP026074950, ISSN: 0921-5093, [retrieved on 20090327], DOI: 10.1016/J.MSEA.2008.12.016 *
YE XIA QIN ET AL: "Properties of <i>In Situ</i> Synthesized Alumina Ceramic Core Composites", KEY ENGINEERING MATERIALS, vol. 368-372, 1 January 2008 (2008-01-01), pages 724 - 725, XP055356522, DOI: 10.4028/www.scientific.net/KEM.368-372.724 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019030025A1 (fr) 2017-08-08 2019-02-14 Morgan Advanced Ceramics, Inc Matériaux céramiques se prêtant à la lixiviation pour le moulage

Also Published As

Publication number Publication date
GB201800344D0 (en) 2018-02-21
GB2553481A (en) 2018-03-07

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