Rare Earth Oxyfluoride Thermal Spray Granules
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Solution Overview
Problem
Conventional thermal spray materials containing rare earth elements face issues such as instability during feeding to thermal spray devices and a high likelihood of the coating separating from the substrate upon thermal shock due to oxidative decomposition and cleavage fracture.
Innovation Solution
A thermal spray material comprising granules with specific particle size, aspect ratio, and compressibility, primarily composed of rare earth oxyfluoride (LnOF), which enhances stability and adhesion to the substrate even under thermal shock conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If granules of rare earth fluoride (LnF3) are used as thermal spray material, then the material provides corrosion protection, but the granules easily break due to cleavage fracture and exhibit unstable feed to thermal spray equipment
Solution Approach 1:
The invention changes the chemical composition parameter from rare earth fluoride (LnF3) to rare earth oxyfluoride (LnOF). This compositional change fundamentally alters the mechanical properties, eliminating cleavage fracture and improving granule strength while maintaining corrosion resistance. The parameter change resolves the contradiction by transforming the material's inherent brittleness into durability.
2Reliability
If granules of rare earth fluoride (LnF3) are used as thermal spray material, then the material provides corrosion protection, but the coating film is liable to separate from the substrate when subjected to thermal shock
Solution Approach 1:
The invention changes the chemical composition from rare earth fluoride to rare earth oxyfluoride, which fundamentally improves thermal shock resistance. The oxyfluoride composition creates a more thermally stable coating that adheres better to the substrate under thermal stress, resolving the contradiction between coating adhesion and thermal shock resistance.
3Ease of manufacture
If firing temperature exceeds 600° C. during granule production, then binder removal is improved, but oxidative decomposition occurs producing oxyfluoride and causing apparent weight loss
Solution Approach 1:
The invention converts the harmful oxidative decomposition effect into a beneficial outcome. Instead of viewing the oxidation at high temperature as a defect to be avoided, the process intentionally produces rare earth oxyfluoride (LnOF) as the desired final compound. The high-temperature firing that previously caused unwanted side reactions now directly creates the improved material composition.
Solution Approach 2:
The invention changes the target chemical composition from rare earth fluoride to rare earth oxyfluoride, which allows for higher firing temperatures during manufacturing. This parameter change enables complete binder removal at temperatures above 600° C. without compromising material stability, as the oxyfluoride structure is inherently more stable at these temperatures.
4Manufacturing precision
If the cumulative volume particle diameter after ultrasonic dispersion is reduced to improve coating quality, then the coating uniformity is improved, but the feeding efficiency to thermal spray equipment may be affected
Solution Approach 1:
The invention changes the granule strength parameter through compositional modification to rare earth oxyfluoride. This creates a unique situation where granules can be dispersed into fine particles (improving coating uniformity) while the individual particles maintain sufficient stability for efficient feeding. The parameter change in material composition resolves the trade-off between particle size and feeding efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The material exhibits improved stability during feeding and forms a durable coating that resists separation from the substrate during thermal shocks, ensuring high flowability and increased strength.
Implementation Method 1
ultrasonic dispersion at 300 W for 15 minutes
Implementation Method 2
thermal spray coating formed on a substrate by using the thermal spray granules
Data Source
AI summary
A thermal spray material comprising granules containing a rare earth oxyfluoride has a particle diameter of 1 to 150 μm at a cumulative volume of 50 vol % before ultrasonic dispersion and 10 μm or smaller after ultrasonic dispersion at 300 W for 15 minutes as determined by laser diffraction/scattering particle size distribution analysis. The particle diameter after ultrasonic dispersion is one-third or less of that before ultrasonic dispersion. The thermal spray material has an average aspect ratio of 2.0 or lower and a compressibility of 30% or less. When the granules further contain a rare earth fluoride, upon being analyzed by X-ray diffractometry using Cu-Kα or Cu-Kα1 radiation, S1/S2 is preferably ≧0.10. S1=intensity of the maximum peak assigned to the rare earth oxyfluoride. S2=intensity of the maximum peak assigned to the rare earth fluoride, both observed in a 2θ angle range of 20° to 40°.