Layered Metal Deposition With Hot Bead Compression for Stronger Bonding
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Solution Overview
Problem
Additive manufacturing methods using successive depositions of molten matter face issues such as residual stress-induced deformation, oxidation, and anisotropy, leading to poor mechanical properties and cohesion between layers.
Innovation Solution
A method involving hot compression of beads immediately after deposition, combined with shot peening or gas compression, to modify stress, harden the material, and remove oxides, thereby improving microstructure and bonding, and using a shared robotic arm with a laser head and nozzles for efficient bead formation and compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If successive depositions of molten matter are used to manufacture parts, then additive manufacturing capability is achieved, but residual stress-induced deformation and poor mechanical properties occur
Solution Approach 1:
The patent applies preliminary action by performing hot compression on the bead immediately after deposition while the material is still hot and pliable. This timing allows the compression to effectively modify the microstructure and reduce residual stresses before the bead fully solidifies, preventing deformation and improving layer cohesion
Solution Approach 2:
The patent changes the physical state parameter of the bead from hot/pliable to compressed/densified by applying compression forces during the hot state. This parameter change enables microstructure modification, grain refinement, and stress relief that would not be possible after complete cooling
2Productivity
If rapid solidification of beads occurs during deposition, then layer-by-layer construction is achieved, but oxidation and poor metallurgical health result
Solution Approach 1:
The patent converts the harmful effect of rapid cooling (which causes oxidation) into a beneficial process by applying hot compression during the hot state. The compression treatment densifies the bead, reduces porosity, and modifies the microstructure in a way that compensates for and overrides the detrimental effects of rapid solidification and oxidation
Solution Approach 2:
The patent creates a protective environment by maintaining the bead in a hot state during compression, which reduces oxidation. The hot compression process itself acts as a protective mechanism by densifying the material and reducing surface area exposure to oxidizing conditions
3Strength
If directional thermal transfer to substrate occurs during deposition, then layer bonding is achieved, but columnar grain growth and material anisotropy result
Solution Approach 1:
The patent applies preliminary action by performing hot compression on each bead before it is completely solidified and before subsequent layers are deposited. This timing allows the compression to disrupt and reorganize the columnar grain structure while the material is still plastic, promoting more equiaxed grain growth and reducing anisotropy
Solution Approach 2:
The hot compression process introduces mechanical deformation and stress to the hot bead material, which disrupts the directional columnar grain growth pattern. The compression forces cause grain refinement and promote more isotropic microstructure development, reducing material anisotropy
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 enhances the mechanical properties of the final part by reducing cracking and anisotropy, improving adherence and microstructure homogeneity, and controlling residual stress and porosity, resulting in improved part quality.
Implementation Method 1
a laser head configured to melt the filler metal for the purpose of creating a bead
Implementation Method 2
the formed bead is compressed, and in that the compression step is performed hot, i.e. before the complete cooling of said bead
Implementation Method 3
the compression step is performed by shot peening said bead
Implementation Method 4
The bead-by-bead or layer-by-layer compression treatment enables the modification/removal of the stress applied to the beads, the hardening of the material of the beads
Implementation Method 5
the compression step is performed... to pickling of oxides, thereby making it possible to treat deformation aspects, the anisotropy of the structure and bonding flaws
Data Source
AI summary
A method for manufacturing at least one portion of a part using successive deposition of layers, involving the steps of: a) depositing a first layer of a molten metal on a substrate such that a first metal strip is formed on the substrate; b) depositing a second layer of a molten metal on the first strip such that a second metal strip is formed on the first strip; and c) repeating steps a) and then b) for each new metal layer to be deposited on a preceding strip until the at least one portion of the part has been formed. The method may further include step d) compressing the formed bead after performing n instances of step c), n being greater than or equal to 1. The step of compressing the formed bead may be performed before the complete cooling of said bead.