Additive Manufacturing Surface Finish via Controlled Oxidation
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Solution Overview
Problem
Existing additive manufacturing methods, such as laser sintering, often result in poor surface finishes on thin-walled structures, leading to issues like excessive pressure drop, thermal inefficiency, and susceptibility to internal oxidation/hot corrosion, due to stress raisers and surface asperities, which conventional surface finishing techniques fail to adequately address without compromising material integrity.
Innovation Solution
A method involving additively manufacturing an article in an inert environment, followed by controlled oxidation in a non-inert environment to form an oxidized layer, which is then removed using ionic liquids or electro-polishing, while optionally relieving stress through heating and controlling environmental conditions like humidity and temperature, to achieve a smooth surface finish without impacting material properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional mechanical surface finishing methods (e.g., abrasive media) are used, then surface finish can be improved, but material removal rate is non-uniform causing wear on fin edges
Solution Approach 1:
The patent replaces mechanical surface finishing methods with electrochemical polishing. Instead of using abrasive media that causes non-uniform material removal, the invention uses electrochemical reactions to uniformly remove material from the surface. The electrochemical polishing cell applies electrical current through an electrolyte solution, creating uniform oxidation and material removal across the entire surface, including fin edges, without the mechanical wear problems of traditional methods.
2Manufacturing precision
If electrochemical polishing with aqueous acids is used, then surface finish is improved, but intergranular attack and oxidation compromise material integrity
Solution Approach 1:
The patent changes the chemical parameters of the electrolyte solution to achieve surface finishing without compromising material integrity. Instead of using strong aqueous acids like nitric, phosphoric, or sulfuric acid that cause intergranular attack, the invention uses a non-aqueous electrolyte or a modified aqueous electrolyte with controlled pH and composition. This parameter change allows electrochemical polishing to proceed while preventing the harmful intergranular oxidation and material degradation associated with conventional acid-based methods.
3Manufacturing precision
If mass finishing techniques with abrasive media are used, then surface asperities can be removed, but the process is time-consuming and non-uniform
Solution Approach 1:
The patent replaces time-consuming mechanical mass finishing processes with electrochemical polishing. The electrochemical method acts simultaneously across the entire surface area, removing asperities uniformly in a single step rather than requiring prolonged mechanical tumbling or blasting. This substitution dramatically reduces processing time while maintaining uniform surface finish quality.
4Ease of manufacture
If thin walled structures are additively manufactured with poor surface finish, then manufacturing complexity is reduced, but thermal performance deteriorates due to excessive pressure drop
Solution Approach 1:
The patent applies electrochemical polishing to thin-walled additively manufactured structures to improve their internal surfaces. By uniformly removing surface asperities and roughness from the thin walls and internal passages, the process reduces flow resistance and pressure drop without requiring complex mechanical finishing operations. This maintains the manufacturing simplicity of additive manufacturing while restoring thermal efficiency by enabling smooth fluid flow through the thin-walled structures.
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 method effectively improves surface finish quality, reduces porosity, and enhances structural integrity by forming a uniform oxidation layer that can be precisely controlled, offering superior thermal performance and material integrity compared to traditional methods, with significant time and cost savings.
Implementation Method 1
allowing at least a portion the article to oxidize in the non-inert environment to form an oxidized layer on a surface of the article
Implementation Method 2
Removing the oxidized layer can include treating the oxidized layer with an ionic liquid. Treating the oxidized layer with an ionic liquid can include electro-polishing to descale the oxidized layer.
Implementation Method 3
The method can further include relieving stress in the article (e.g., via heating the article after additive manufacturing).
Data Source
AI summary
A method includes additively manufacturing an article in an inert environment, removing the article from the inert environment and placing the article in a non-inert environment, allowing at least a portion the article to oxidize in the non-inert environment to form an oxidized layer on a surface of the article, and removing the oxidized layer (e.g., to smooth the surface of the article). The method can further include relieving stress in the article (e.g., via heating the article after additive manufacturing).