Sacrificial Shell Fabrication for Contaminant-Free Metal Components
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Solution Overview
Problem
Powder bed fusion techniques often result in contaminated metallic components due to impurities from the melt pool, leading to reduced mechanical properties, especially in components subjected to high thermal and mechanical stresses.
Innovation Solution
The method involves additively manufacturing a sacrificial shell with complementary geometry, evacuating contaminated powder through integral ports, filling it with a highly-pure pulverant material, and undergoing a high-temperature and high-pressure consolidation process, such as HIP, to achieve near 100% theoretical density and homogenous microstructure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If powder bed fusion techniques are used to create metallic components, then complex geometries can be achieved, but the build powder becomes contaminated with impurities from the melt pool
Solution Approach 1:
The component manufacturing process is segmented into two distinct stages: first, a sacrificial shell with the desired complex geometry is additively manufactured; second, this shell is evacuated and filled with high-purity powder for consolidation. This segmentation allows the geometric complexity to be achieved in the shell while the final component is formed from contaminant-free powder.
Solution Approach 2:
The contaminated powder is extracted and removed from the system by evacuating it through integral ports in the sacrificial shell. This extraction eliminates the harmful impurities from the melt pool, preventing their incorporation into the final component while preserving the ability to create complex geometries.
2Ease of manufacture
If impurities are incorporated into the component during manufacturing, then the component can be produced, but mechanical properties are reduced
Solution Approach 1:
The sacrificial shell is preliminarily manufactured with the exact geometry of the desired component, creating a mold that defines the final shape. This preliminary action allows the final component to be formed from high-purity powder without contamination, preserving mechanical properties while enabling production.
Solution Approach 2:
The process creates a controlled environment by evacuating the sacrificial shell to remove contaminated atmosphere and powder, then filling with high-purity pulverant material. This inert environment prevention ensures no impurities are incorporated during consolidation, maintaining superior mechanical properties.
3Strength
If a sacrificial shell is additively manufactured and filled with high-purity powder, then components with improved mechanical properties can be achieved, but the process complexity increases
Solution Approach 1:
The sacrificial shell manufacturing and the component formation processes are merged into a single integrated system. The shell includes integral ports that serve dual functions: facilitating evacuation of contaminated powder and enabling filling with high-purity material. This merging reduces the need for separate handling operations and equipment.
Solution Approach 2:
The sacrificial shell is designed to be self-serving by including integral ports that automatically facilitate the evacuation and filling processes. The shell structure itself provides the necessary functionality for process control, eliminating the need for external complex equipment to manage powder removal and replacement.
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 approach enables the fabrication of components with complex geometries and improved mechanical properties, suitable for high-stress applications like aerospace, by removing impurities and achieving full density and homogeneity.
Implementation Method 1
a consolidating heating apparatus to a temperature and for a period of time sufficient to densify the pulverant material to near 100% theoretical density
Implementation Method 2
a consolidating pressing apparatus to a pressure sufficient to densify the pulverant material to near 100% theoretical density
Data Source
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AI summary
A method of fabricating a near net shape component includes forming a sacrificial shell (12) from a pulverant material (18) using an additive manufacturing process, the shell having an aperture (14). The method further includes filling the shell with a second pulverant material, subjecting the filled shell to a consolidation process, and removing the shell from the consolidated second pulverant material.