YAG Plasma Spray Coating With Intersecting Cooling for Dense Crystallinity
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Solution Overview
Problem
Conventional spray coating methods for yttrium aluminate-containing coatings result in amorphous states due to rapid cooling, leading to suboptimal property values and porosity issues, especially when attempting to achieve high densification and resistance to chemical and physical etching.
Innovation Solution
A plasma spray coating method involving a granular powder with crystalline YAG, where a plasma stream forms molten droplets that are then cooled by an intersecting coolant stream, allowing for the formation of a coating with both crystalline and amorphous phases, enhancing densification and hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional spray coating is used with YAG material, then the coating can be formed, but the rapid cooling causes the material to remain in an amorphous state resulting in low hardness and high porosity
Solution Approach 1:
The invention changes the thermal parameters of the spray coating process by introducing a pre-heating zone that raises the temperature of the coating layer before the molten material impacts it. This temperature control parameter change enables the YAG material to crystallize properly upon impact, transforming it from an amorphous state to a crystalline state with enhanced hardness and reduced porosity
Solution Approach 2:
The invention introduces a gas stream as an intermediary medium between the plasma jet and the substrate. This gas stream serves as a heat transfer medium that pre-heats the coating layer, allowing controlled thermal conditions for crystallization without direct contact between the plasma and substrate, thus resolving the contradiction between forming the coating and achieving high crystallinity
2Manufacturing precision
If heat treatment is applied to crystallize YAG coating, then crystallinity may improve, but the crystallization temperature of 900°C or higher makes it substantially impossible to crystallize the sprayed coating
Solution Approach 1:
The invention performs preliminary heating of the coating layer through the pre-heating zone before the actual deposition occurs. This preliminary thermal action prepares the substrate surface and intermediate layers at appropriate temperatures so that when the molten YAG material impacts, it crystallizes immediately upon contact, eliminating the need for subsequent high-temperature heat treatment
3Manufacturing precision
If plasma output is reduced to increase crystallization, then the degree of crystallization may increase slightly, but property values decrease and porosity increases
Solution Approach 1:
The invention segments the plasma spray process into distinct functional zones: a plasma generation zone, a pre-heating zone with controlled gas flow, and a deposition zone. This segmentation allows the pre-heating zone to specifically address crystallization needs through controlled thermal conditions, while the deposition zone maintains optimal plasma parameters for forming dense, high-property coatings without excessive porosity
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 method achieves a high degree of crystallization (45% or more) and low porosity (1-3.1%) in the sprayed coating, resulting in improved Vickers hardness (1000-1110 for crystalline phase) and resistance to plasma etching, thereby addressing the limitations of conventional spray coating techniques.
Implementation Method 1
forming molten droplets of the granular powder by supplying the granular powder to the plasma stream
Implementation Method 2
forming molten droplets of the granular powder
Implementation Method 3
providing a coolant stream in a direction intersecting the plasma stream containing the molten droplets
Implementation Method 4
The sprayed coating has a microstructure in which a crystalline phase and an amorphous phase are alternately present
Data Source
AI summary
Disclosed is a method for plasma spray coating for a sprayed coating containing YAG, which provides a method for manufacturing a plasma sprayed coating, the method comprising: providing a granular powder containing crystalline YAG; forming a plasma stream toward a base material from a plasma spray torch; forming molten droplets of the granular powder by supplying the granular powder to the plasma stream; providing a coolant stream in a direction intersecting the plasma stream containing the molten droplets; and providing the base material with the plasma stream that has undergone the coolant stream, thereby forming a sprayed coating containing a crystalline phase and an amorphous phase.