Casting mold for directional solidification of an alloy

• US 3,973,750 A
• Filed: 07/07/1975
• Issued: 08/10/1976
• Est. Priority Date: 10/06/1972
• Status: Expired due to Term

• Current Assignee: Office National D'Etudes et de Recherches Aerospatiales
• Original Assignee: Office National D'Etudes et de Recherches Aerospatiales
• Inventors: Rabinovitch, Maurice, Bibring, Herve
• Primary Examiner(s): Husar, Francis S.
• Assistant Examiner(s): Rowold, Carl
• Application Number:
  US05/593,669
• Time in Patent Office: 400 Days
• Field of Search: 249/114, 164/60, 164/72, 164/137, 164/341, 164/364
• US Class Current: 249/114.1
• CPC Class Codes: B22C 23/02 Devices for coating moulds or cores
• CPC Class Codes: B22D 27/045 Directionally solidified castings
• CPC Class Codes: C30B 21/02 by normal casting or gradient freezing

Abstract

A mold for obtaining metallic parts with an orientated crystalline struct by the directed solidification of an alloy is disclosed. The mould comprises a body of refractory mold that is a good heat conductor and on the inner wall of said body is provided a chemically protective lining of dense refractory metal oxide, with a high degree of purity, deposited on said body by blowpipe projection as a thin non-porous layer. The thickness of the metal oxide lining is in the order of a tenth of a millimeter to five tenths of a millimeter, the oxide being choosen in the group constituted by aluminium oxide, zirconium oxide, magnesium oxide and thorium dioxide with a degree of purity at least equal to 99.5 %.

Claims

1. A mold for the directional solidification of a metal alloy composite to produce a refractory directionally solidified polyvariant fiber-reinforced composite having eutetic-type structure consisting essentially of two distinct independent phases constituted by:

a. a complex multicomponent matrix phase consisting essentially of;

i. at least one metal selected from the group consisting of Fe, Ni and Co, and

ii. chromium in an amount between 10 and 25 percent by weight of the composite;

and in said matrix;

b. an in situ grown reinforcing phase free from chromium and consisting essentially of whisker-like elongated monocrystalline fibers of at least one metal monocarbide, the metal of which is selected from the group constituted by Ta, Nb, Hf and Ti, said mold comprising an elongated hollow body composed of a refractory material selected from the group which consists of graphite, tungsten, molybdenum, and tantalum, and a thermally blow-pipe applied coating of a refractory metal oxide coating the interior of said body in a uniform-thickness layer of a thickness of substantially 0.1 to 0.5 mm and of a porosity of at most 10%, said refractory metal oxide being selected from the group which consists of aluminum oxide, and having a purity of at least 99.5%, said body and said layer being dimensioned to permit a solidification rate of 0.5 to 6 cm/hour for alloys having a melting point of 1300°

C to 1400°

C and heated to a temperature of 1700°

C to 1750°

C.

2. The mold defined in claim 1 wherein said coating is applied from a plasma.

3. The mold defined in claim 1 wherein said coating is applied by flame spraying.

4. in the formation of a metal object by the directional solidification of a metal alloy, said alloy having a composition adapted to produce a refractory directionally solidified polyvariant fiber-reinforced composite having eutectic-type structure consisting essentially of two distinct independent phases constituted by:

a. a complex multicomponent matrix phase consisting essentially of;

i. at least one metal selected from the group consisting of Fe, Ni and Co, and

ii. chromium in an amount between 10 and 25 percent by weight of the composite;

and in said matrix;

b. an in situ grown reinforcing phase free from chromium and consisting essentially of whisker-like elongated monocrystalline fibers of at least one metal monocarbide, the metal of which is selected from the group constituted by Ta, Nb, Hf and Ti, said alloy being melted in an elongated mold along which a solidification interface is shifted with a high temperature gradient across said interface to form said matrix phase and said reinforcing phase the improvement wherein said mold is reusable after each formation of an object therein and comprises a hollow mold body of a heat resistant material of high thermal conductivity selected from the group which consists of graphite, tungsten, molybdenum and tantalum, and wherein said body is internally coated before each use with a uniform-thickness layer of a refractory metal oxide by thermal blow pipe coating, said refractory metal oxide being aluminum oxide, with a purity of at least 99.5%, said coating being carried out to form a layer of the thickness of 0.1 to 0.5 mm with a porosity of at most 10%, said body and said layer being dimensioned to permit a solidification rate of 0.5 to 6 cm/hour for alloys having a melting point of 1300°

C to 1400°

C and heated to a temperature of 1700°

C to 1750°

C.