Method for thermal spray coating and rare earth oxide powder used therefor
First Claim
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.
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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.
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Citations
11 Claims
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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.- View Dependent Claims (2, 3, 4, 5, 6, 7)
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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. - View Dependent Claims (10)
- a globular particle configuration with an aspect ratio not exceeding 2;
- 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.
Specification