Laser Peened Component Post Processing to Remove Remelt Layer
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Solution Overview
Problem
Laser peening processes often result in a damaged remelt layer on metal components, such as turbine engine parts, due to the use of the base metal as an ablative medium, leading to micro-cracking and detrimental tensile residual stresses, which requires effective post-processing methods for removal and surface finishing.
Innovation Solution
A method involving grit blasting, chemical etching, and mechanical finishing to remove and refine the laser remelt layer, ensuring a depth removal of less than 1 mil (0.0254 mm) to restore the component surface, specifically tailored for turbine engine components like airfoils, blades, vanes, and shafts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the base metal surface is used as an ablative medium during laser peening, then the plasma generation and shock wave formation are improved, but the base metal surface becomes damaged with micro-cracking and tensile residual stresses
Solution Approach 1:
The patent introduces a sacrificial ablative layer as an intermediary material between the laser and the base metal surface. This layer absorbs the laser energy and undergoes ablation to generate plasma and shock waves, protecting the base metal from direct laser-induced damage. The ablative layer serves as a mediator that enables the beneficial effects of laser peening while preventing the harmful remelt layer formation.
Solution Approach 2:
The patent employs a disposable sacrificial ablative layer that is intentionally designed to be consumed during the laser peening process. This temporary material is applied to the surface, performs its protective function during laser irradiation, and is then removed along with the damaged remelt layer through post-processing, leaving the base metal intact and undamaged.
2Strength
If laser peening is performed using the base metal as ablative material, then deep compressive residual stresses are induced, but a damaged remelt layer is created requiring additional post-processing steps
Solution Approach 1:
The sacrificial ablative layer acts as a protective intermediary that enables the laser peening process to generate the desired compressive residual stresses without directly damaging the base metal surface. By absorbing the laser energy and undergoing controlled ablation, the ablative layer prevents the formation of a damaged remelt layer on the component, thereby eliminating or reducing the need for extensive post-processing surface finishing operations.
3Object-affected harmful factors
If a sacrificial ablative layer is applied to protect the base metal during laser peening, then base metal damage is prevented, but additional materials and processing steps are required
Solution Approach 1:
The sacrificial ablative layer serves as a temporary intermediary that simplifies the overall manufacturing process by preventing base metal damage during laser peening. Although it adds a preparation step, it eliminates the need for extensive post-processing to remove damaged remelt layers, thereby reducing total process complexity and improving manufacturing efficiency.
Solution Approach 2:
The patent applies the sacrificial ablative layer as a preliminary protective measure before the laser peening process. This pre-application ensures that the base metal surface is protected from damage during the high-energy laser irradiation, and the layer is subsequently removed along with any minimal damaged material, streamlining the overall manufacturing sequence.
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
This multi-step process effectively removes the damaged remelt layer, improving the surface condition of metal components by addressing micro-cracking and residual stresses, enhancing the damage tolerance and finish of turbine engine parts.
Implementation Method 1
When the laser hits the material, an explosion of expanding plasma is formed between the ablative layer and the water layer. This explosion of plasma creates a shock wave that compresses and works the outer layer of the material.
Implementation Method 2
This explosion of plasma creates a shock wave that compresses and works the outer layer of the material.
Implementation Method 3
grit blasting a surface at a remelt layer
Implementation Method 4
chemically etching the surface
Implementation Method 5
mechanically finishing the surface
Data Source
AI summary
A method of post processing a laser peened component to remove a laser remelt layer is proposed. The post processing includes a series of steps including grit blasting, chemical etching and mechanical finishing the component. This will ensure that the mechanical property (i.e., damage tolerance) benefit of laser peening is restored to the surface of the component.