Quantifying additive manufacturing could help repair high-value components

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Optical microscopy images show the impact face (top surface) in each sample. Original wrought material appears lighter in color while the repair region is darker and shows a fish-scale-like pattern. The spall plane is evident in the center of each sample. Charts to the right indicate the net damage in the vertical direction across the region (indicated by the blue rectangular box in the microscopy image).

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Additive manufacturing (AM) has the potential to be used for repair of high-value parts, and thus avoiding challenges associated with low production volume and high startup costs. However, the strength and integrity of such repaired parts, especially under dynamic loading, is still largely unknown. To employ AM technology in repair applications requires quantifying the process-structure-properties-performance relationship — that is, understanding how these components interconnect to affect the material’s ultimate behavior.

In Acta Materialia, Los Alamos materials researchers present the results of additively repaired stainless steel samples subjected to high strain-rate dynamic tests — addressing key elements not covered in existing published research on AM repairs. Despite minor differences in the materials’ properties, the overall dynamic response of the original material and repaired samples was similar, suggesting that AM is a promising approach for repairing high-value components.

In the study, the researchers created intentional surface defects of varying sizes in stainless steel samples. The surface damage was repaired using electron beam additive manufacturing. The repaired samples were then subjected to high strain-rate impacts using a gas-gun launched flyer plate, with sample velocity measured using photon Doppler velocimetry. The recovered samples then underwent optical microscopy and electron backscatter diffraction analysis. This analysis clearly showed that overall the equation of state and failure in the repaired components was similar to the un-paired components. However, as the defect depth was increased and this repaired region coincided with the region of maximum tension, changes in the void morphology were observed. This suggests that there might be a critical volume fraction of a component that that can be repaired before the dynamic properties are altered. 

Future research efforts may focus on alternative processing parameters or post-repair treatments to achieve a more homogeneous grain structure and better match the behavior of the repair to the original material.

The work leverages Sigma Division’s manufacturing science expertise and capabilities — particularly its machining and additive repair operations — and the Center for Integrated Nanotechnologies’ quasi-static and dynamic materials diagnostic and dynamic behavior of materials experimental capabilities and expertise.

Funding and mission

This work, funded by U.S. Department of Energy National Nuclear Security Administration, supports the Materials for the Future capability pillar.

Reference

“Dynamic properties of 316L stainless steel repaired using electron beam additive manufacturing,” Acta Materialia 246, 118636 (2023); DOI: 10.1016/j.actamat.2022.118636. Authors: Jesse G. Callanan, Amber N. Black, Samantha K. Lawrence, David R. Jones, Daniel T. Martinez, Ramon M. Martinez and Saryu J. Fensin (Los Alamos National Laboratory).

Technical contact: Saryu Fensin (MPA-CINT)