Method for thermal spray coating and rare earth oxide powder used therefor

• US 20020018902A1
• Filed: 06/29/2001
• Published: 02/14/2002
• Est. Priority Date: 06/29/2000
• Status: Active Grant

• Current Assignee: Shin-Etsu Chemical Company Limited
• Original Assignee: Shin-Etsu Chemical Company Limited
• Inventors: Maeda, Takao, Takai, Yasushi, Tsukatani, Toshihiko
• Granted Patent: US 6,576,354 B2
• Time in Patent Office: Days
• US Class Current: 428/469
• CPC Class Codes: C23C 4/11 Oxides
• 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 428/26 Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
• CPC Class Codes: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]

Abstract

The invention discloses an efficient method for the formation of a highly corrosion— or etching-resistant thermal spray coating layer of a rare earth oxide or rare earth-based composite oxide by a process of plasma thermal spray method by using a unique thermal spray powder consisting of granules of the oxide. The thermal spray granules are characterized by a specified average particle diameter of 5 to 80 μm with a specified dispersion index of 0.1 to 0.7 and a specified BET specific surface area of 1 to 5 m²/g as well as a very low content of impurity iron not exceeding 5 ppm by weight as oxide. The flame spat powder used here is characterized by several other granulometric parameters including globular particle configuration, particle diameter D₉₀, bulk density and cumulative pore volume.

Claims

1. A thermal spray coating layer of a rare earth compound or a rare earth-based composite formed on a substrate surface by a thermal spray coating method which comprises the step of:

spraying particles of the rare earth compound or rare earth-based composite at the substrate surface as being carried by a flame, the particles having an average particle diameter in the range from 5 to 80 μ

m with a dispersion index in the range from 0.1 to 0.7 and a specific surface area in the range from 1 to 5 m²/g and the content of iron as an impurity in the particles not exceeding 5 ppm by weight calculated as iron oxide.

2. The thermal spray coating layer of a rare earth compound or a rare earth-based composite on a substrate surface as claimed in claim 1 in which the particles of the rare earth compound or rare earth-based composite are granules of primary particles of the rare earth compound or rare earth-based composite having an average particle diameter in the range from 0.05 to 10 μ

m.

3. The thermal spray coating layer of a rare earth compound or a rare earth-based composite on a substrate surface as claimed in claim 1 in which the flame is a plasma flame.

4. The thermal spray coating layer of a rare earth compound or a rare earth-based composite on a substrate surface as claimed in claim 2 in which the granules of the rare earth compound or rare earth-based composite have an average particle diameter in the range from 20 to 80 μ

m.

5. The thermal spray coating layer of a rare earth compound or a rare earth-based composite on a substrate surface as claimed in claim 2 in which the granules of the rare earth oxide or rare earth-based composite oxide are prepared by granulating the primary particles of the rare earth compound or rare earth-based composite in an aqueous slurry containing a binder resin into a granular form and calcining the granulated primary particles at a temperature in the range from 1200 to 1800°

C. for 1 to 10 hours.

6. The thermal spray coating layer of a rare earth compound or a rare earth-based composite on a substrate surface as claimed in claim 5 in which the amount of the binder resin is in the range from 0.1 to 5% by weight based on the amount of the primary particles of the rare earth compound or rare earth-based composite.

7. The thermal spray coating layer of a rare earth compound or a rare earth-based composite on a substrate surface as claimed in claim 1 which has a thickness in the range from 50 to 500 μ

m.

8. A powder of a rare earth compound or a rare earth-based composite for thermal spray coating consisting of particles having:

a globular particle configuration with an aspect ratio not exceeding 2;

a particle diameter value D₉₀ not exceeding 60 μ

m for the 90% by weight level in the particle size distribution;

a bulk density not exceeding 1.6 g/cm³; and

a cumulative pore volume of at least 0.0 2 cm³/g for the pores having a pore radius not exceeding 1 μ

m.

10. The powder of a rare earth compound or a rare earth-based composite for thermal spray coating as claimed in claim 8 in which the rare earth compound and the rare earth-based composite are a rare earth oxide and a rare earth-based composite oxide, respectively.

9. A powder of a rare earth compound or a rare earth-based composite for thermal spray coating in which the content of iron group elements, the content of alkali metal elements and the content of alkaline earth metal elements each do not exceed 5 ppm by weight.

11. The powder of a rare earth compound or a rare earth-based composite for thermal spray coating as claimed in claim 9 in which the rare earth compound and the rare earth-based composite are a rare earth oxide and a rare earth-based composite oxide, respectively.