Abstract
To ensure consistent performance of additively manufactured metal parts, it is advantageous to identify alloys that are robust to process variations. This paper investigates the effect of steel alloy composition on mechanical property robustness in laser-directed energy deposition (L-DED). In situ blending of ultra-high-strength low-alloy steel (UHSLA) and pure iron powders produced 10 compositions containing 10–100 wt.% UHSLA. Samples were deposited using a novel configuration that enabled rapid collection of hardness data. The Vickers hardness sensitivity of each alloy was evaluated with respect to laser power and interlayer delay time. Yield strength (YS) and ultimate tensile strength (UTS) sensitivities of five select alloys were investigated in a subsequent experiment. Microstructure analysis revealed that cooling rate-driven phase fluctuations between lath martensite and upper bainite were a key factor leading to high hardness sensitivity. By keeping the UHSLA content ≤20% or ≥70%, the microstructure transformed primarily to ferrite or martensite, respectively, which generally corresponded to improved robustness. Above 70% UHSLA, the YS sensitivity remained low while the UTS sensitivity increased. This finding, coupled with the observation of auto-tempered martensite at lower cooling rates, may suggest a strong response of the work hardening capability to auto-tempering at higher alloy contents. This work demonstrates a methodology for incorporating robust design into the development of alloys for additive manufacturing.
Recommended Citation
J. Kelley et al., "Development of Robust Steel Alloys for Laser-Directed Energy Deposition Via Analysis of Mechanical Property Sensitivities †," Micromachines, vol. 15, no. 10, article no. 1180, MDPI, Oct 2024.
The definitive version is available at https://doi.org/10.3390/mi15101180
Department(s)
Materials Science and Engineering
Second Department
Mechanical and Aerospace Engineering
Publication Status
Open Access
Keywords and Phrases
alloy design; high-strength low-alloy steel; in situ alloying; laser-directed energy deposition; powder blend; robustness; sensitivity analysis
International Standard Serial Number (ISSN)
2072-666X
Document Type
Article - Journal
Document Version
Final Version
File Type
text
Language(s)
English
Rights
© 2024 The Authors, All rights reserved.
Creative Commons Licensing
This work is licensed under a Creative Commons Attribution 4.0 License.
Publication Date
01 Oct 2024
Comments
Missouri University of Science and Technology, Grant W911NF-20-2-0251