Corrosion and wear resistant graphite material

• US 4,617,232 A
• Filed: 04/15/1982
• Issued: 10/14/1986
• Est. Priority Date: 04/15/1982
• Status: Expired due to Fees

• Current Assignee: Carborundum Universal Investment Limited (Compagnie de Saint-Gobain SA)
• Original Assignee: Kennecott Corporation (Alcan)
• Inventors: Amra, Lutfi H., Chandler, Richard C.
• Primary Examiner(s): Ives, Patricia C.
• Application Number:
  US06/368,700
• Time in Patent Office: 1,643 Days
• Field of Search: 428/408, 428/323, 428/328, 428/698, 428/699, 428/689, 427/249, 427/250
• US Class Current: 428/328
• CPC Class Codes: C04B 35/52 based on carbon, e.g. graphite
• CPC Class Codes: C04B 41/009 characterised by the material treated
• CPC Class Codes: C04B 41/4521 application under increased pressure
• CPC Class Codes: C04B 41/4531 by C.V.D.
• CPC Class Codes: C04B 41/4535 applied as a solution, emulsion, dispersion or suspension
• CPC Class Codes: C04B 41/4554 the coating or impregnating material being an organic or organo-metallic precursor of an inorganic material
• CPC Class Codes: C04B 41/5059 Silicon carbide
• CPC Class Codes: C04B 41/5092 Phosphate cements
• CPC Class Codes: C04B 41/52 Multiple coating or impregnating multiple coating or impregnating with the same composition or with compositions only differing in the concentration of the constituents, is classified as single coating or impregnation
• CPC Class Codes: C04B 41/89 for obtaining at least two superposed coatings having different compositions
• CPC Class Codes: F04B 15/04 the fluids being hot or corrosive for liquids near their boiling point, e.g. under subnormal pressure, F04B15/06
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/256 Heavy metal or aluminum or compound thereof
• CPC Class Codes: Y10T 428/30 Self-sustaining carbon mass or layer with impregnant or other layer

Abstract

The invention provides a composite carbon or graphite having desirable properties such as corrosion and wear resistance. The invention combines a graphite substrate with a protective porous zone of silicon carbide. The whole body of graphite plus silicon carbide then is infiltrated with aluminum phosphate. An adhered barrier of silicon carbide, ranging in thickness between 0.015 and 0.050 inch thick is integrated with a graphite stratum to form a very hard surface, resistant to mechanical and chemical wear. The silicon carbide barrier is closely compatible to the graphite substrate, in resistance to thermal shock and in qualities of thermal expansion. In order to improve oxidation resistance further, a new composition was formed by infiltrating aluminum phosphate through the silicon carbide into the graphite to form a single body of composite graphite.

Claims

1. An article for use in high temperature environments such as molten metal pumps, furnace liners, and the like, comprising:

(a) an internal composition consisting substantially of a carbonaceous material formed of molded or extruded graphite, particles of aluminum phosphate being distributed in the internal composition; and

(b) a surface composition highly resistant to oxidation and erosion consisting substantially of a layer of silicon carbide, particles of aluminum phosphate being distributed throughout the surface composition.

2. The article of claim 1, wherein the surface composition extends to a depth of about 0.035-0.045 inch.

3. In a molten metal pump wherein components formed of a molded or extruded carbonaceous material come into contact with molten metal, the improvement comprising:

an oxidation and erosion resistant finish applied to the carbonaceous components that come into contact with molten metal, the finish including an outer layer of silicon carbide, and particles of aluminum phosphate distributed throughout the silicon carbide layer and into at least a portion of the carbonaceous material.

4. The molten metal pump of claim 3, wherein the silicon carbide layer extends from the surface to a depth on the order of 0.035-0.045 inch.