Date of Award
2026-08-01
Degree Name
Doctor of Philosophy
Department
Mechanical Engineering
Advisor(s)
Eric MacDonald
Abstract
Laser hot-wire directed energy deposition (LHW-DED) offers high deposition rates and efficient material use, but the resistively preheated wire introduces an additional energy input that must be controlled in concert with the laser power, wire delivery, melt pool behavior, and the accumulating thermal history of the part. This dissertation develops a multimodal in-situ stability mapping framework for LHW-DED. The framework combines infrared thermography, coaxial optical imaging, and computer-vision segmentation, each validated against post-process characterization, across three experimental phases. First, interlayer infrared thermography was applied to detect subsurface cavities in stainless steel 316LSi builds. A gradient heat-flow analysis resolved intentional cavities from 4.0 to 6.5 mm, in agreement with X-ray computed tomography, and a transient heat transfer simulation confirmed the physical basis of the method. Second, near-coaxial imaging quantified process stability under varying laser and hot-wire power. Laser power was the primary driver of melt pool growth and substrate penetration, whereas hot-wire power acted as a transfer-stabilizing variable. Melt pool area alone was insufficient as a stability indicator; SAM2-derived wire metrics (intersection over union, volatility, and angle variability) provided complementary indicators, validated by cross-sectional metallography. Third, the framework was extended to multilayer builds at three wire-to-travel-speed ratios, with and without interlayer temperature control. Temperature control roughly halved the per-layer exposure above 1000 °C, at a three- to four-fold build-time cost. The combined metrics resolved underbuilding, stable, and overbuilding regimes that no single metric could distinguish on its own. EBSD revealed a uniform 5.1 - 6.3% ferrite fraction across all conditions, which indicates that process departures manifested geometrically rather than microstructurally. This work demonstrates that robust evaluation of LHW-DED stability requires joint interpretation of thermal, melt pool, and wire signatures. These validated in-situ metrics support future closed-loop control and in-process qualification of wire based directed energy deposition.
Language
en
Provenance
Received from ProQuest
Copyright Date
2026-08
File Size
163 p.
File Format
application/pdf
Rights Holder
Mario Alberto Rodriguez Parra
Recommended Citation
Rodriguez Parra, Mario Alberto, "Multimodal In-Situ Stability Mapping For Laser Hot-Wire Directed Energy Deposition" (2026). Open Access Theses & Dissertations. 4779.
https://scholarworks.utep.edu/open_etd/4779