United States

In the realm of laser powder bed fusion, an emerging field with significant growth potential, we still find ourselves at a pioneering stage characterized by the intricate interplay between laser beam properties and their interaction with powdered material.  It is commonly assumed that a high-quality laser having a low M2 value would maintain a consistent M2 value uniformly across the build plate.  However, contrary to this assumption, variations do occur across the build plate, not due to fluctuations in the laser&#39;s M2 value, but rather due to alterations in the beam&#39;s geometry.  Even in scenarios where the F-theta lens or the 3-D galvo system operate at diffraction-limited conditions, the reality persists that a Gaussian beam with a low M2 value positioned at the nominal zero-zero point of the galvo system will inevitably lose its circular profile at positions beyond the zero-zero point.  At non-zero angles, the beam undergoes distortion, presenting itself to the powdered material as a conic section of the single-mode Gaussian beam.  Employing an innovative M2 measurement apparatus, we have quantified the M2 variation inherent in a fiber laser galvo scanning system across a scan field measuring 175mm x 175mm.  This understanding of the M2 variant holds significant promise in facilitating the stabilization of an optimal spot size.  Through dynamic focusing adjustments based on the powder bed&#39;s positional information, we can effectively compensate for the observed variance, thereby enhancing the overall performance and reliability of the laser powder bed fusion process.

ICALEO 2024

M2 Projection Variant in Laser Powder Bed Fusion Systems

m2 measurement

m2 variant

lpbf

laser beam diagnostics

laser powder bed fusion

  #### Welcome to the 43rd annual ICALEO!

Attention laser enthusiasts, innovators, and industry leaders! Get ready to immerse yourself in the exciting world of lasers at the 43rd annual ICALEO conference. This year, we gathered in the iconic city of Hollywood, California, for cutting-edge technology, groundbreaking presentations, and unparalleled networking opportunities.
Whether you're a seasoned professional or new to the field of photonics, the 43rd annual ICALEO had something for everyone. 

#### General Chair Welcome Message

It is with immense joy and anticipation that I extend a warm welcome to each and every one of you as the General Chair of this year's ICALEO conference.

This year, we find ourselves in the iconic setting of Hollywood, serving as a fitting backdrop for the extraordinary developments in laser technology and applications unfolding in our community.

Our main sessions cover a diverse range of topics, from the intricacies of micro and nano processing to the transformative power of laser additive manufacturing. We will explore the frontiers of battery technology, delve into the intricate world of artificial intelligence, and witness the seamless integration of lasers into these realms.

For those joining us for the first time, we extend an especially heartfelt welcome. ICALEO is not just a conference; it's a convergence of minds, ideas, and innovations. Beyond the formal sessions, I encourage you to engage in informal exchanges. The spirit of discovery and camaraderie is as much a part of the ICALEO experience as the scheduled sessions.

Thank you for being a part of ICALEO 2024. Whether you are a returning participant or a first-time attendee, your presence adds immeasurable value to our vibrant community. May this conference be, this year again, a catalyst for inspiration, collaboration, and breakthroughs that will resonate in our community and beyond.

Eric Mottay<br>
Congress General Chair, ICALEO 2024


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#### Program Tracks
Below is the list of all tracks that were on ICALEO 2024 Conference.

##### Laser Additive Manufacturing
* The Laser Additive Manufacturing (LAM) track is a forum to explore the latest innovations and research in laser-based additive manufacturing (LAM). The Laser Additive Manufacturing track focuses on diverse topics, including laser-based powder bed fusion (PBF-LB), directed energy deposition (DED), and other emerging techniques revolutionizing modern manufacturing processes. From materials science to process optimization, from design innovation to industrial implementation, this track connects researchers, engineers, and industry leaders to exchange insights and share breakthroughs in laser additive manufacturing.

##### Laser Materials Macroprocessing
* The Macroprocessing track comprises some of the most productive laser processing applications. Although these applications have been broadly adopted, researchers and industry are persistently innovating to provide new techniques and novel technologies to advance macro materials processing. The attendees will share and discuss those exciting achievements of their research with peers in these macroscopic specialized sessions.

##### Laser Materials Microprocessing
* The Microprocessing track will consist of papers and talks featuring a wide spectrum of applications and innovative equipment for materials processing in microscales with a strong focus on processes with Short and Ultrashort Pulsed Lasers. The presentations will introduce the latest and greatest advancements in their respective fields, presented by world-leading companies and research organizations. This year we will have talks around the headlines of “Beam shaping”, “Glass”, “Surface processing” and “Drilling” between other topics.

##### Frontiers in Laser Applications
* The Frontier in Laser Applications (FLA) track explores recent, cutting-edge applications of lasers, highlighting innovation at the transition of research and industry. The track has included presentations from a variety of fields: Novel 3-D Printing, Advanced Manufacturing, Laser Manufactured Devices, and Frontiers in Laser Processing. The sessions under the Frontier in Laser Application track promise to bring diverse and unique perspectives from real-world applications across laser manufacturing.

##### Laser in Battery Manufacturing
* Electrification is crucial to address global environmental challenges. The laser plays a key role in most manufacturing steps in battery production with all possible laser applications from ablation, structuring, welding, cutting, and marking. Further improvements in the batteries’ power densities, fast charging properties, and yield in battery production are related to photonics and, thus, lasers. We will hear and discuss the latest developments in research, development, and industrial applications. Join us for this year’s Battery Track.

##### Artifical Intelligence in Laser Processing
* The track ‘Artificial Intelligence in Laser Processing’ at ICALEO 2024 explores the fusion of AI and laser manufacturing. Discover cutting-edge research on optimizing laser processes and enhancing manufacturing efficiency. Explore AI’s diverse applications in parameter optimization, quality prediction, real-time process monitoring, and control. Join us to unlock the potential of AI-driven solutions revolutionizing laser materials processing, delivering unprecedented precision, productivity, and innovation.
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Attention laser enthusiasts, innovators, and industry leaders! Get ready to immerse yourself in the exciting world of lasers at the 43rd annual ICALEO conference. 

In the realm of laser powder bed fusion, an emerging field with significant growth potential, we still find ourselves at a pioneering stage characterized by the intricate interplay between laser beam properties and their interaction with powdered material.  It is commonly assumed that a high-quality laser having a low M2 value would maintain a consistent M2 value uniformly across the build plate.  However, contrary to this assumption, variations do occur across the build plate, not due to fluctuations in the laser's M2 value, but rather due to alterations in the beam's geometry.  Even in scenarios where the F-theta lens or the 3-D galvo system operate at diffraction-limited conditions, the reality persists that a Gaussian beam with a low M2 value positioned at the nominal zero-zero point of the galvo system will inevitably lose its circular profile at positions beyond the zero-zero point.  At non-zero angles, the beam undergoes distortion, presenting itself to the powdered material as a conic section of the single-mode Gaussian beam.  Employing an innovative M2 measurement apparatus, we have quantified the M2 variation inherent in a fiber laser galvo scanning system across a scan field measuring 175mm x 175mm.  This understanding of the M2 variant holds significant promise in facilitating the stabilization of an optimal spot size.  Through dynamic focusing adjustments based on the powder bed's positional information, we can effectively compensate for the observed variance, thereby enhancing the overall performance and reliability of the laser powder bed fusion process.

technical paper

Smart-Alloying enables local modification of the chemical composition of metallic components within additive manufacturing processes. This new method represents an innovative process for localized grading of metallic materials in laser-based additive manufacturing. Smart-Alloying involves applying nanoparticulate alloying elements onto the surfaces of additive manufactured components in precise doses using suspensions. The method is shown here using a laser powder bed fusion (PBF-LB/M) as an example. By coating the base material powder and exposing it to the laser source, localized modifications in chemical composition and altered properties can be achieved. Using a chromium-rich ferritic stainless steel as an example, significant alterations in the fundamental microstructure are attained through localized re-alloying of carbon. Investigation utilizing FIB-SEM elucidate the evolution of increasing carbon content within the re-alloyed area. Next to the formation of chromium-rich carbides and ultrafine regions of needle-like martensite, retained austenite could be made visible. The completely renewed microstructure is then further modified using secondary exposures of the laser source. Under the influence of the subsequent melting process, there is an increasing distribution of the re-alloyed carbon, resulting in a completely new structure of a line-shaped duplex microstructure. The integration of secondary exposure introduces a completely novel aspect, offering the potential to merge localized grading via Smart-Alloying with targeted application of laser parameters.

Smart-Alloying for Tailored Microstructures in Laser-Based Metal Additive Manufacturing

The trajectory of metal additive manufacturing is transitioning from rapid prototyping towards on-demand and serial production. Consequently, the paramount objective remains the enhancement of additive manufacturing processes like laser-based powder bed fusion of metals (PBF-LB/M) to meet modern manufacturing needs and reduce environmental impact. Shielding gas flow significantly influences mechanical properties in PBF-LB/M by protecting metal from oxidation and removing process by-products from the powder melting zone. Accordingly, improper shielding gas flow distribution can result in poor part quality, excessive inert gas consumption, and contamination of the building chamber. Presently, a lack of consensus remains regarding which configuration of shielding gas supply is most appropriate in terms of process efficiency. This is the comprehensive investigation of a localized and vertically directed shielding gas flow and its effects on the properties of parts, also taking into account the reduction of inert gas consumption. In contrast to previous investigations, it is shown that enhanced surface roughness and relative density of the parts, as well as minimized contamination of the optics inside the building chamber is achieved through more efficient removal of metal plume particles from the processing zone by localized gas flow. Moreover, the developed computational fluid dynamics (CFD) simulation model enabled the efficient determination of particularly promising gas flow configurations. Furthemore, the validation of the simulation model is demonstrated in an experimental environment. Finally, by localizing shielding gas flow, energy consumption can be reduced by almost half.

Enhancing the Efficiency of Laser-based Powder Bed Fusion of Metals through the Use of Localized and Vertically Directed Shielding Gas Flow

Laser cladding with wire feeding is an advanced surface modification technology that has experienced significant growth in recent decades due to its high deposition rate,

efficient material utilization, strong metallurgical bonding, low dilution ratio, and minimal heat-affected zone. Despite these advantages, the thermo-physical and metallurgical mechanisms underlying the laser wire cladding process are complex, making it challenging to identify the interrelationships among materials, design, process parameters, and performance using traditional expertise or conventional expert systems. This study presents a comprehensive overview of process development, parameter optimization, numerical simulations, and real-time sensing in laser hot-wire cladding using a high-power direct diode laser. A mathematical model was developed to correlate geometric characteristics and dilution ratios with laser processing parameters, establishing the desired process window to enhance deposition rates and achieve high-quality clad layers. To address the effects of residual stresses on mechanical integrity and fatigue life, a three-dimensional uncoupled thermo-mechanical finite element model was developed to predict temperature evolution and thermally induced residual stress distribution in cladding process. Furthermore, a multi-sensor monitoring system, integrating a high-speed camera, spectrometer, and infrared camera, was employed to detect real-time variations in cladding conditions. This study also introduces the concept of a digital twin for the laser wire cladding system, aimed at providing interactive feedback among materials, design, process parameters, and performance to enhance the overall process control and quality.

Laser Cladding with Wire Feeding Using a High Power Direct Diode Laser: Process Fundamentals, Numerical Simulation, and Real-time Monitoring

Electrochemical reduction of CO2 and H2O to synthesize gas (H2 and CO mixture) is of significant interest due to established industrial pathways to tune the H2 to CO composition to generate an array of valuable products including methanol, synthetic fuel, synthetic natural gas, and hydrogen. However, controlled H2:CO ratios are challenging on CO-active electrocatalysts like silver. We demonstrate that applying laser engineering to adjust the surface wetting state of a silver electrocatalyst with water contact angles θw ranging from 47° and 135°, H2:CO ratios can be tuned from 1 to 4 at modest potentials (-0.7 V vs. RHE, RHE - reversible hydrogen electrode) with almost total unity Faradaic efficiency. Both hydrophilic (θw = 47°) and more hydrophobic (θw = 135°) samples showed an increasing H2:CO trend with rising potentials (0.7 V - 1.2 V vs. RHE) due to mass transport. Conversely, a silver electrocatalyst with θw = 110° exhibited a constant H2:CO ratio of 4. This indicates catalyst wettability potentially affects *H and *HOCO intermediates' adsorption, impacting H2:CO ratios. Our results show the feasibility of syngas composition control on silver catalysts via surface wettability, providing a simpler alternative to complex multicomponent electrocatalytic systems. These findings open new avenues for the design of electrocatalysts with tailored syngas production capabilities, which could have significant implications for the sustainable production of chemicals and fuels.

Fine-Tuning Syngas Composition using Laser Surface Modified Silver Electrode for CO2 Electroreduction

With high-speed laser melt injection (HSLMI), it is possible to generate wear-resistant metal matrix composite (MMC) surfaces on tools with great productivity. Since high laser intensities are required for reaching high process speeds, strong interactions between powder particles and the laser beam can occur. In order to reduce the interaction time and to receive a better understanding of the role of particle transport in the HSLMI process, trajectories of spherical fused tungsten carbide (SFTC) particles were analyzed by high-speed imaging. The trajectories were divided into the path from the powder nozzle to the weld pool surface and the incorporation path. First, it was investigated how the travel time is affected by the volume flow rate of the feeding gas and by the powder feed rate. Second, the incorporation of the SFTC particles was analyzed and the incorporation time was measured. It was found that the volume flow rate has a decisive influence on both the travel time and the incorporation time of the particles. Consequently, an increased volume flow rate lead to a significant reduction of the interactions between SFTC particles and the laser beam. Furthermore, a decrease in incorporation time was determined towards the center of the weld pool. Whereas the majority of the SFTC particles was incorporated immediately, some particles dwelled on the surface of the weld pool before being incorporated.

Influencing the Powder Particle Transport in High-Speed Laser Melt Injection

We discuss the direct fabrication of embedded, graphitized features within high-purity, synthetic single-crystal diamond through ultrafast laser micromachining, for the purpose of creating narrow conductive plates in diamond. As an incorporating substrate, carbon in the form of highly pure synthetic diamond offers numerous advantageous physico-chemical properties, including hardness, durability, optical transparency, and extremely high electrical resistance. On the other hand, graphitic carbon can exhibit exceptionally low electrical resistance. For example, sandwich structures consisting of a thin sheet of diamond between two sheets of graphite with areal dimensions of 5 × 1 mm2 and 1 µm gaps between plates may be formed and evaluated. To realize these forms of regionally converted diamond, we employ ultrafast laser micromachining with high numerical aperture focusing and precise positioning control to disrupt the crystalline matrix of a well-confined volume within single-crystal synthetic diamond, forming embedded graphitic features. Graphitized plate regions 1 µm thick with 1 µm separations can be fabricated in this manner, and empirical I-V measurements indicate resistances as low as ~kΩ. We compare plates formed through both Gaussian and Bessel-beam focusing techniques, and we also address challenges involved with fabricating closely parallel, embedded graphitic plates in thick diamond substrates, including aberration, machining time, and cracking.

Development of Embedded Graphitic-Sandwich Structures in Single-Crystal Synthetic Diamond via Ultrafast Laser Micromachining

Laser powder bed fusion (PBF-LB) has established itself as an industrial process for the manufacturing of complex metal parts for lightweight applications. The increasing prevalence of PBF-LB parts, as well as the increasing functional integration and size limitations of PBF-LB machines are leading to a growing demand for joining processes for PBF-LB parts.

However, one limitation for laser welding of PBF-parts, especially aluminum parts, are porous weld seams with volatile mechanical properties. Therefore, this work investigates the impact of the PBF-LB process parameters and the resulting part properties on the overall weld seam quality of laser-welded AlSi10Mg PBF parts.

In a first step PBF-LB specimens with different porosities regarding relative density, pore shape and pore size were manufactured with experimentally defined process parameters. Subsequently specimens were laser welded in three different configurations (lap joint, butt joint and bead on plate welding). Cross-sections of the weld seams were metallographically prepared to investigate the overall porosity and pore sizes as well as the local pore distribution and local hardness deviations in the weld seam. Tensile tests were carried out to assess the impact on the load bearing capacity of the weld seam. Similar experiments were done using conventional aluminum cast and sheet material and results were compared.

The investigation showed that the weld seam porosity of laser-welded AlSi10Mg PBF-parts is significantly higher compared to conventional aluminum materials, but does not depend on the initial porosity of the joined PBF-parts, but rather on the PBF process parameters and the resulting microstructure.

Impact of the Process Parameters and Part Properties from the Laser Powder Bed Fusion (PBF-LB) Process on the Weld Seam Quality of Laser-Welded AlSi10Mg PBF-LB-Parts

Femtosecond lasers have over the past ten years seen a tremendous increase in average power, with industrial laser reaching today the kW level. At the same time new applications are continuously emerging in various industrial sectors: health, production, energy, transport. Femtosecond laser processing is today a technology enabling large volume, high precision industrial manufacturing. The "agility" of lasers and associated beam engineering now available, enables flexible, reconfigurable production. High average power femtosecond lasers allow higher productivity and thus open access to new and large markets unreachable so far (Aeronautics, Energy and Mobility, etc.). Making full use of the available average power without losing the high quality of ultrafast laser processing is not straightforward and require advances in laser design and associated beam engineering. For instance, high laser repetition rate up to 10 MHz or temporal shaping of the pulse train with busts of pulses, allows specific process optimization with the use of beam deviation at very high speed if suited pulses synchronisation is possible. Spatial shaping, for instance by dividing a single high-power beam into multiple beamlets, will be also a “must have” in the following years. Fixed diffractive optics (DOE), user configurable optical tools (spatial light modulators, SLM, or AOM), and new shaping systems using multi-plane light conversion (MPLC) technology allow flexibility to transform both phase and amplitude of a laser beam without major losses.

Coupling High-power Femtosecond Lasers and Beam Engineering for Industrial Application Challenges

Additive manufacturing of metals is becoming increasingly important in various industrial sectors, including aviation and space, the energy sector and the automotive and toolmaking industries. More so than with other manufacturing processes, the quality of AM components is based on an in-depth understanding of the interactions between the AM process, the resulting material and the component properties.

This lecture will highlight the coaxial nozzle design approach for powder and wire AM of high-grade materials, including light metals, nickel and titanium alloys, bronze, hard metals or high-entropy alloys. Based on the material properties and the desired component specifications, customized processing heads for coaxial feeding of the material to the laser beam at the working position are available, compatible with conventional laser systems and hybrid AM machines. Some nozzles have been optimized for the use in extreme conditions or confined spaces, while others are designed for particularly fine structures or for high-grade materials. In a recent concept, wire and powder filler material have been combined in one head, opening new horizons in 2D and 3D DED manufacturing. Exemplary components for the aerospace industry as well as high productive laser cladding applications for the automotive and oil and gas industry will be discussed.

Combined Wire and Powder DED for Combinatorial Materials Development and High Productivity LAM

Significant research efforts have been undertaken over the past forty years to replace cobalt-based StelliteTM alloys, which offer outstanding performance when used as hardfacing coatings, but have proved problematic in radioactive environments. The aim of this work is to contribute to this effort by proposing viable substitutes made from multi-principal element alloys (MPEAs). Laser cladding process has demonstrates its very good capacity to generate deposit with high tribological properties. Moreover, a large number of compositions can be generated in different samples or samples with graded compositions thanks to the inline fusion of powders provided from different powder feeders. Combined with an intensive use of the thermodynamic calculation using CALPHAD (Thermo-Calc) method, this strategy considerably accelerates material development compared with more conventional methods. Initial work has highlighted the (CrFeNi)90Mo5Ti5 alloy as a promising base that relies on the formation of intermetallic phases within a ductile matrix for increased hardness and improved tribological behavior. The optimization of the composition made by tuning of the hard phase (sigma phase) in the material, which is driven by the combination of Mo,Cr and Fe elements. The proposed iterative process of calculation, experimentation and material characterization demonstrates the possibility of tailoring material composition to functional properties comparable or even better than the Stellite 6 alloy.

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Smart-Alloying for Tailored Microstructures in Laser-Based Metal Additive Manufacturing

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