Laser-Roughened Ceramic Substrates for Thermal Spray Adhesion
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Solution Overview
Problem
Surface roughening techniques, such as blasting, often result in reduced substrate strength and inadequate adhesion of thermal sprayed coatings on ceramic substrates due to microcracks and variations in surface texture, while laser machining provides less physical impact but insufficient adhesion.
Innovation Solution
Laser irradiation of ceramic substrates under specific conditions (power density of 1.0×10^7-1.0×10^9 W/cm² and action time of 1.0×10^-7-1.0×10^-5 s) to create a roughened surface with a thin oxide layer, which enhances adhesion and prevents substrate strength reduction by covering microcracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If blasting is used to roughen the substrate surface, then adhesion of thermal sprayed coating is improved, but substrate strength is reduced due to microcracks
Solution Approach 1:
The patent replaces the mechanical blasting process with laser irradiation to roughen the substrate surface. The laser beam (electromagnetic energy) substitutes for the mechanical impact of blasting particles, achieving surface roughening without causing microcracks that would compromise substrate strength. This is explicitly stated in the background section where conventional blasting is contrasted with the laser-based method of the present invention.
Solution Approach 2:
The patent controls the laser irradiation parameters (power density, pulse duration, scanning speed) to achieve optimal surface roughening while preventing substrate damage. By adjusting these parameters within specific ranges, the method achieves sufficient surface roughness for coating adhesion without exceeding the threshold that would cause microcrack formation and strength reduction.
2Strength
If laser irradiation is used to roughen the substrate surface, then substrate strength is maintained, but adhesion of thermal sprayed coating is insufficient
Solution Approach 1:
The patent optimizes laser irradiation parameters including power density (10^4-10^7 W/cm²), pulse duration (10^-9-10^-5 s), and scanning speed to achieve surface roughness within a specific range (Ra 0.1-10 μm). These parameter adjustments ensure sufficient surface roughening for coating adhesion while preventing substrate damage, directly addressing the adhesion insufficiency problem.
Solution Approach 2:
The patent employs pulsed laser irradiation rather than continuous irradiation. The periodic pulse structure (with durations from nanoseconds to milliseconds) allows for controlled energy delivery that achieves surface roughening while providing cooling intervals that prevent excessive heat accumulation and substrate damage, thereby improving coating adhesion without compromising substrate integrity.
3Shape
If conventional laser irradiation is used to roughen the substrate surface, then surface roughening is achieved, but microcracks are formed reducing substrate strength
Solution Approach 1:
The patent defines specific ranges for laser parameters: power density (10^4-10^7 W/cm²), pulse duration (10^-9-10^-5 s), and scanning speed (1-1000 mm/s). These parameter changes ensure that the laser energy is sufficient to create surface roughness (Ra 0.1-10 μm) but remains below the threshold that would cause microcrack formation and substrate strength reduction.
Solution Approach 2:
The patent uses pulsed laser irradiation with carefully controlled pulse durations (10^-9-10^-5 s). The periodic nature of the pulses allows for controlled material removal and surface modification while providing cooling intervals between pulses that prevent excessive heat accumulation and microcrack formation, thus achieving surface roughness without compromising substrate strength.
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 strong adhesion and high durability of thermal sprayed coatings on ceramic substrates with maintained substrate strength, suitable for structural members requiring high strength.
Implementation Method 1
roughening a surface of a ceramic substrate by laser irradiation
Implementation Method 2
a surface layer of the ceramic substrate is melted by the laser beam
Implementation Method 3
a surface layer of the ceramic substrate is melted by the laser beam and is oxidized in atmospheric air
Data Source
AI summary
A ceramic substrate is irradiated in an atmospheric air with a laser having a power density of 1.0×107-1.0×109 W/cm2 for an action time on an irradiation area of 1.0×10−7-1.0×10−5 s to roughen a surface of the ceramic substrate, as well as to form an oxide layer on a roughened surface. A thermal sprayed coating formed on the ceramic substrate sufficiently adheres to the ceramic substrate via the oxide layer.