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ATU Sligo

Mechanical, Microstructural, and Corrosion Analysis of DED-Repaired 316SS After Fracture

In this study, the repair performance of Directed Energy Deposition (DED) on fractured 316 stainless steel (316SS) samples is evaluated. Samples were first manufactured in flat, horizontal, and vertical build orientations and fractured through tensile testing to determine their initial mechanical behaviour. Following breakage, the specimens were repaired using DED with matching 316SS material. Subsequent mechanical testing, including tensile strength measurements, was performed to assess the recovery of mechanical properties after repair. Additionally, detailed fractography, microstructural characterization, and corrosion studies were conducted to understand the quality and integrity of the repaired regions. This work aims to provide insights into the mechanical, structural, and corrosion performance of DED-repaired 316SS components and to develop a deeper understanding of how build orientation and post-fracture repair influence the overall material behaviour. The findings are expected to support future applications of additive repair techniques in critical industries where 316SS is commonly used.

Dublin City University

Co-authors: David Kinahan (Dublin City University), Dermot Brabazon (Dublin City University)

Volumetric Energy Density Optimization and Phase Control in NiTi for Enhanced Sustainability and Functional Performance in Additive Manufacturing

This study explores Laser Powder Bed Fusion (LPBF) processing of NiTi shape memory alloys using a two-level design of experiments varying scan speed, layer thickness, and hatch spacing. The influence of volumetric energy density (VED) on part density, microhardness, surface quality, and phase formation were investigated. Higher VEDs (46.3–92.6 J/mm³) yielded near-theoretical densities (~98.9%) and enhanced microhardness (up to 297.67 HV), attributed to improved melting and reduced porosity. Excessive VED, however, led to localized grain coarsening. Surface roughness decreased at higher VEDs, and XRD/EDX analyses confirmed phase composition. These findings underline the importance of energy input optimization in LPBF-fabricated NiTi alloys.

Dublin City University

Multi-Sensor In-Situ Monitoring and Porosity Prediction in Powder Bed Fusion of Nitinol (NiTi)

Co-authors: Mert Celikin (University College Dublin), Claudia Mazo (Dublin City University), Dermot Brabazon (Dublin City University)

Powder Bed Fusion-Laser Beam (PBF-LB) is widely used in biomedical manufacturing for its precision in producing complex geometries, though porosity remains a key challenge. This study integrates acoustic emission and infrared thermography sensors into a PBF-LB system to monitor the fabrication of Nitinol (NiTi) samples under varying process parameters. A 4×4 full factorial design was used, and porosity was assessed via the Archimedes method. Machine learning algorithms were developed to predict  density outcomes, forming a digital twin model for porosity prediction and future control. This approach enables the framework for adaptive processing and improved quality control for NiTi components.

Dublin City University

Investigation of Recrystallization and Grain Growth Kinetics of IN718 Fabricated by Laser Powder Bed Fusion

This study examines the recrystallization and grain growth behavior of IN718 alloy fabricated by laser powder bed fusion (L-PBF) under three different heat treatment temperatures (1050 °C, 1150 °C, and 1250 °C) and holding times (15, 45, and 90 minutes). Electron backscatter diffraction (EBSD) was used to characterize texture evolution. The as-built microstructure featured bowl-shaped melt pools, a chessboard-like grain pattern, and a strong cube texture {100}<001>. Recrystallization initiated at regions of high dislocation density—particularly melt pool overlaps and grain boundaries. At 1150 °C for 15 minutes, initial recrystallization was observed, with a texture transition to {122}<212> attributed to twinning-assisted mechanisms. Further annealing led to the expansion of recrystallized grains with minimal new twinning activity. Nearly full recrystallization occurred at 1250 °C, producing a weaker cube texture and a stronger P-orientation {011}<112>. Grain growth remained limited due to the pinning effect of non-coherent precipitates.

South East Technologicial University

Co-authors: Abhijit Cholkar (South East Technological University), Dermot Brabazon (Dublin City University), Ronan McCann (Dublin City University and South East Technological University), Ramesh Raghavendra (South East Technological University)

Inkjet Printing of Silver Nanoparticle Inks for Conductive Tracks in Printable Electronic Applications

The demand for compact, flexible electronics has focused research on nanomaterials to reduce size and achieve novel flexibility while offering enhanced electrical characteristics. This work will focus on the optimisation of piezoelectric-pneumatic inkjet printing of silver nanoparticle inks onto flexible, polymer substrates for high resolution conductive tracks and coatings. Post-print sintering will also be investigated and optimised. Characterisation techniques will include adhesion and bend tests for mechanical durability, 4-point probe conductivity and microscopy to determine optimum conditions to achieve repeatability and uniformity. Ultimately, this research aims to improve the feasibility of inkjet printing as an electronic device manufacturing process.

Dublin City University

Mechanical Characterisation of PBF-LB and Heat-Treated Nickel-Rich NiTi Lattice Structures

Co-authors: Joseph Michael Doyle, Lehar Asip Khan, Ankur Majumdar, Dermot Brabazon

Nickel-rich NiTi alloys produced through metal additive manufacturing (AM) allow for the creation of complex shapes with minimal post-processing. This study focused on manufacturing porous NiTi lattice structures using laser powder bed fusion (PBF-LB), followed by detailed mechanical, thermal, and physical characterization. A 10% variation in strut diameters of the printed samples was observed compared to CAD models. The energy-dispersive X-ray spectroscopy (EDX) revealed a nickel loss of up to 1 at.% with the final part still with a predominantly austenitic parent phase. Full-field stress- displacement analysis showed the as-printed lattices achieved a peak energy absorption efficiency of 21.03%. Experimental stress strain results aligned well with preduiction from Auricchio’s model for phase transformation stress-strain. Extending this work, the heat-treated NiTi lattice structures were examined to understand how post-processing affects microstructural evolution, phase transformation, mechanical properties, and overall performance, thereby providing insights into optimizing these additively manufactured NiTi lattices for advanced applications.

Atlantic Technological University

The Application of Metal Additive Manufacturing Technologies to Post-Process Biomedical Metallic Surfaces

Co-authors: Marion McAfee (Atlantic Technology University and University College Dublin), Ramesh Raghavendra (University College Dublin, South East Technological University) , Dermot Babazon (Dublin City University), Merve Nur Dogu (Dublin City University), Meris Ikiz (Dublin City University), Usman Aziz (Atlantic Technology University and University College Dublin), David Tormey (Atlantic Technology University and University College Dublin) 

This work gives an overview of the progress on post-processing of biomedical metal surfaces, leveraging metal additive manufacturing (AM) to produce, process and control biomedical implant surface properties. This presentation will provide an overview of the developed AM-assisted post-processing workflow, which has been tested on AM 316L stainless steel using AM copper electrodes and also adapted for use on AM NiTi shape memory alloy. The primary focus of the work is to reduce the material, energy consumption and processing steps for manufacturing implants and improve the surface characteristics of biomedical components while controlling their mechanical and biomedical performance.

South East Technological University

Co-authors: Abhijit Cholkar (South East Technological University), Ronan McCann (South East Technological University and Dublin City University), David Culliton (South East Technological University), Ramesh Ragavendra (South East Technological University)

Optimizing Laser Powder Bed Fusion alloy feedstocks via Nanoparticle reinforcement

Laser Powder Bed Fusion (LPBF) is gaining traction across a variety of sectors due to its ability to fabricate intricate geometries, while minimizing material waste. However, achieving optimal material properties such as low porosity remains a key challenge with this technique. In this study, Ti-6Al-4V is reinforced with Graphene Oxide (GO) to fabricate LPBF parts. The resulting build is systematically characterised, and its mechanical and microstructural properties compared with parts produced from using Ti-6Al-4V. The aim of this is to enhance the material properties of LPBF-fabricated components, offer improved performance and expand its applicability in advanced manufacturing sectors.

Dublin City University

Co-authors: Rakesh Nair (Dublin City University), Lorna Fitzsimons (Dublin City University), Dermot Brabazon (Dublin City University)

Effect of metal additive manufacturing process parameters on oxide build up

This study mimics the recycled nitinol powder. The samples were heated at three different temperatures at different intervals in three grades of argon concentrations. An Oxygen sensor is attached to the outlet to monitor the oxygen concentration. A measuring system was used for calibration models using pyrometry to determine emissivity. Microstructures were monitored using an in-line camera during heating. Characterization techniques included SEM-EDX, microhardness, nanohardness, XPS, and OES. Results have indicated the effects of temperature on reflectance; a correlation between the effect of the processing temperature on oxidization; and the process parameters on the material properties of the powder.

Dublin City University

3D printed nickel based alloys as anode material for sodium ion batteries

Co-authors: Anesu Nyabadza (Dublin City University), Sithara P. Sreenilayam (Dublin City University), Dermot Brabazon (Dublin City University)

Sodium-ion batteries have emerged as a promising alternative to conventional lithium-ion batteries due to their comparable electrochemical performance. However, the technical challenges related to stabilising cathodes, anodes, and electrolytes hinder the development of sodium-ion batteries like lithium-ion batteries. The anode material should be highly conductive and maintain a voltage close to pure sodium. Sodium-ion batteries typically avoid using pure sodium as the anode because it reacts with organic electrolytes, forming an unstable and ineffective passivation layer. Various forms of carbon, transition metal oxides, alloys, metal oxides, sulphides, and organic composites have been used as anode material for developing sodium-ion batteries. This work introduces 3D printed nickel based alloy as an anode for developing sodium ion batteries. Its high electrical conductivity, chemical stability, and surface properties have the potential to lead to enhance battery performance. These developments offer a promising strategy for creating an anode material to advance high-performance sodium-ion batteries.

University College Dublin

Co-authors: Andrea Villano (University College Dublin)

Real-Time Defect Detection in Sustainable Additive Manufacturing with Edge Computing Machine Learning Models

This study presents a machine learning-based approach for real-time defect detection in sustainable additive manufacturing. Sensor data from 3D printers are analyzed by trained models to identify defects such as porosity as they occur, enabling immediate corrective actions. The system reduces material waste, energy consumption, and production errors by detecting issues early in the process. Continuous model adaptation improves detection accuracy and minimizes false positives. This approach supports higher product quality, resource efficiency, and sustainable manufacturing practices.