Institute of Fundamental Technological Research

Abstract:
This study investigates the use of high-frequency eddy current testing (ECT) to assess the structural integrity of aluminide coatings on MAR-M247 nickel superalloy under simulated fatigue conditions. Aluminide coatings, deposited via chemical vapor deposition at thicknesses of 20 µm and 40 µm, were tested using custom-designed probes optimized for defect detection. Results demonstrate that substrate grain structure and coating thickness significantly influence coating durability, with fine-grain substrates exhibiting the least resistance changes and greatest fatigue tolerance. Eddy current signal variations correlated with microstructural changes, enabling detection of damage otherwise invisible to traditional methods. These findings establish ECT as a precise, non-destructive approach for monitoring aluminide coatings in critical applications.

Keywords:
Nickel alloys, Aluminide coating, Non-destructive testing, Eddy current testing

Abstract:
In this paper, the fracture surface topography of additively manufactured Haynes 282 alloy subjected to tensile and high-cycle fatigue loading was investigated. Haynes 282 alloy bars were printed in three different directions relative to the base plate (0°, 45°, and 90°) via Direct Metal Laser Sintering (DMLS) under an argon protective atmosphere. The specimens were subjected to monotonic tensile loading and fatigue testing under load control using full tension and compression cyclic loading (R = −1) in the range of stress amplitude from ±550 MPa to ±800 MPa. The entire surface topography was evaluated by using a 3D non-contact confocal technique and post-failure specimens after a fatigue test performed at three stress amplitudes, ±650 MPa, ±700 MPa and ±750 MPa. Such an attempt was proposed to analyse the fatigue response of AM Haynes 282 in the region near its yield strength. It was found that the printing orientation and the stress amplitude have a strong impact on service life and fracture surface characteristics. Finally, a surface topography parameter involving the mass density of furrows, root-mean-square height, and fractal dimension was successfully combined with the stress amplitude to estimate the fatigue life. The findings offer a novel approach to fatigue life prediction based on post-failure surface analysis, providing valuable insights for industrial applications and forensic engineering.

Keywords:
Nickel alloys,Fatigue,Additive manufacturing,Direct Metal Laser Sintering (DMLS),Fracture,Surface topography

Abstract:
This study investigates the effects of formate-based deicing agents, specifically potassium formate (HCOOK) and sodium formate (HCOONa), on alkali-silica reaction (ASR) in concrete. By adapting ASTM C1260 standards, mortar bars were subjected to deicing solutions of varying concentrations to evaluate their influence on mortar expansion and ASR product characteristics. Results revealed that high concentrations of formate solutions significantly accelerated ASR, inducing expansions comparable to or greater than those caused by sodium hydroxide, while sodium chloride showed minimal expansion effects. Microstructural and chemical analyses demonstrated that ASR gels formed in formate solutions were predominantly amorphous, with different chemical composition depending on the deicer type. Pore solution analysis indicated a strong correlation between alkali ion concentration and mortar expansion. Furthermore, mechanical testing of ASR products revealed that gels formed in potassium formate exhibited higher hardness and elastic modulus compared to those formed in sodium formate. These findings enhance understanding of the detrimental effects of formate-based deicing agents on ASR and provide a foundation for developing mitigation strategies to preserve concrete infrastructure.

Keywords:
Alkali-silica reaction,Concrete microstructure,Expansion,Nanoindentation,Deicing agents,Pore solution analysis

Abstract:
The study investigates the role of the topology of the additively manufactured AlSi10Mg cellular structures in the example of 3D and 2D designs: honeycomb, auxetic, lattice and foam. The samples were subjected to quasistatic and blast-induced dynamic compression. As a result, a relation between the structural geometry and the deformation mode of the compressed structures has been developed, demonstrating its influence on the energy absorption characteristics. The deformation and fracture mechanisms were examined in detail using the finite element simulations in the LS-DYNA code based on the material characterisation over a broad range of strain rates and temperatures. The outcomes show an agreement between the experimental data and the computations. The obtained results prove that by selecting the appropriate topological features, the deformation of compressed structures can be enhanced to improve their energy-absorption capacity.

Keywords:
Additive manufacturing,AlSi10Mg,Direct metal laser sintering (DMLS),Cellular structures,Dynamic compression,Blast-energy absorption,Explosively-driven shock tube

Abstract:
The present study contributes to the development of alternative materials for radiation shielding, focusing on environmental sustainability and material cost efficiency. The primary aim was to evaluate the compressive and flexural strength, mineral composition, microstructure, and gamma-ray attenuation properties of cement mortars and geopolymer mortars containing barite powder. Mortars based on ordinary Portland cement (OPC) and fly ash geopolymers with varying amounts of barite powder were assessed for their shielding properties at energy levels associated with the decay of 137Cs. From the results, key parameters such as the linear attenuation coefficient (μ), mass attenuation coefficient (μm), half-value layer (HVL), and tenth-value layer (TVL) were determined. The results showed that while cement-based composites exhibited superior gamma radiation attenuation compared to fly ash geopolymer mortars, the latter had higher mass attenuation efficiency, meaning less material density was required for the same level of shielding. Additionally, cement mortars had 23–25 % higher mechanical strength than geopolymer mortars. Importantly, the inclusion of barite powder improved the radiation shielding performance of both materials by 7–10 %, demonstrating its effectiveness in enhancing the protective properties of these mortars. This research highlights the potential of fly ash geopolymer mortars as viable, eco-friendly alternatives to traditional cement mortars in radiation shielding applications.

Keywords:
Cement mortar, Fly ash geopolymer mortar, Barite, Gamma ray attenuation, Microstructure

Keywords:
corrosion, DMLS, haynes 282, nickel superalloy, hydrogen , oxidation

Abstract:
Additive manufacturing (AM) methods, popularly known as 3D printing technologies, particularly the pioneering laser stereolithography (SLA), have revolutionized the production of complex polymeric components. However, challenges such as anisotropy, resulting from the layer-by-layer construction method, can affect the thermomechanical properties and dimensional stability of 3D-printed objects. Although anisotropy in SLA 3D printing is often overlooked due to the high precision of this technique, its impact on the properties and structural performance of the 3D-printed prototype becomes more significant when printing small devices designed for precise micro-mechanisms. This experimental study investigates the impact of the chosen printing surface – a less explored factor – on the performance of SLA 4D-printed thermo-responsive shape memory epoxy (SMEp) specimens. Two identical dog-bone specimens were printed from two distinct surfaces: edge and flat surface, to examine how variations in surface area and quantity of layers influence the microstructure, thermal behavior, mechanical properties, and shape memory performance. The results of this experimental investigation reveal that specimens printed from the edge, with a higher number of layers and smaller surface area, exhibit superior interlayer bonding, tensile strength, dimensional stability, and shape recovery efficiency compared to those printed from the flat surface. Conversely, specimens with fewer, larger layers demonstrated greater elongation and thermal expansion but reduced structural integrity and shape recovery performance. These results highlight the importance of experimentally investigating how different build orientations affect the properties and performance of SLA 3D-printed materials, especially before designing and employing them in applications demanding high precision and reliability.

Keywords:
Additive manufacturing, Laser stereolithography, Shape memory polymers, Materials processing, Anisotropy, Printing orientation

Abstract:
Background Metal Laser Powder Bed Fusion Melting (LPBF-M) is considered economically viable and environmentally
sustainable because of the possibility of reusing the residual powder feedstock leftover in the build chamber after a part
build is completed. There is however limited information on the fatigue damage development of LPBF-M samples made
from reused feedstock.
Objective In this paper, the stainless steel 316 L (SS316L) powder feedstock was examined and characterised after 25
reuses, following which the fatigue damage development of material samples made from the reused powder was assessed.
Methods The suitability of the powder to LPBF-M technology was evaluated by microstructural observations and measurements of Hall flow, apparent and tapped density as well as Carr’s Index and Hausner ratio. LPBF-M bar samples in three
build orientations (Z – vertical, XY – horizontal, ZX – 45° from the build plate) were built for fatigue testing. They were
then subjected to fatigue testing under load control using full tension and compression cyclic loading and stress asymmetry
coefficient equal to -1 in the range of stress amplitude from ± 300 MPa to ± 500 MPa.
Results Samples made from reused powder (25 times) in the LPBF-M process exhibited similar fatigue performance to fresh
unused powder although a lower ductility for vertical samples was observed during tensile testing. Printing in horizontal
(XY) and diagonal (ZX) directions, with reused powder, improved the service life of the SS316L alloy in comparison to
the vertical (Z).
Conclusions Over the 25 reuses of the powder feedstock there was no measurable difference in the flowability between the
fresh (Hall Flow: 21.4 s/50 g) and reused powder (Hall Flow: 20.6 s/50 g). This confirms a uniform and stable powder feeding
process during LPBF-M for both fresh and reused powder. The analysis of fatigue damage parameter, D, concluded cyclic
plasticity and ratcheting to be the main mechanism of damage.

Keywords:
SS316L ,Stainless steel,Fatigue,Additive manufacturing,Laser Powder Bed Fusion Melting (LPBF-M)

Abstract:
This study focuses on the development and characterization of a bulk Ti-Al-N
multiphase composite enriched with BN addition and sintered through hot pressing. The
research aimed to create a material with optimized mechanical and corrosion-resistant
properties suitable for demanding industrial applications. The composite was synthesized using a powder metallurgy approach with a mixture of AlN, TiN, and BN powders, processed under a high temperature and pressure. Comprehensive analyses, including microstructural evaluation, hardness testing, X-ray tomography, and electrochemical corrosion assessments, were conducted. The results confirmed the formation of a multiphase microstructure consisting of TiN, Ti₂AlN and Ti₃AlN phases. The microstructure was uniform with minimal porosity, achieving a hardness within the range of 500–540 HV2. Electrochemical tests revealed the formation of a passive oxide layer that provided moderate corrosion resistance in chloride-rich environment. However, localized pitting corrosion was observed under extreme conditions. The study highlights the potential of a BN admixture to enhance mechanical and corrosion-resistant properties and suggests directions for further optimization in sintering processes and material formulations.

Keywords:
AlN-TiN(BN) composite,hot-pressing,μCT,corrosion resistance

Abstract:
The widespread adoption of metal implants in orthopaedics and dentistry has revolutionized medical treatments, but concerns remain regarding their biocompatibility, toxicity, and immunogenicity. This study conducts a comprehensive literature review of traditional biomaterials used in orthopaedic surgery and traumatology, with a particular focus on their historical development and biological interactions. Research articles were gathered from PubMed andWeb of Science databases using keyword combinations such as “toxicity, irritation, allergy, biomaterials, corrosion, implants, orthopaedic surgery, biocompatible materials, steel, alloys, material properties, applications, implantology, and surface modification”. An initial pool of 400 articles was screened by independent reviewers based on predefined inclusion and exclusion criteria, resulting in 160 relevant articles covering research from 1950 to 2025. This paper explores the electrochemical processes of metals like iron, titanium, aluminium, cobalt, molybdenum, nickel, and chromium post-implantation, which cause ion release and wear debris formation. These metal ions interact with biological molecules, triggering localized irritation, inflammatory responses, and immune-mediated hypersensitivity. Unlike existing reviews, this paper highlights how metal–protein interactions can form antigenic complexes, contributing to delayed hypersensitivity and complications such as peri-implant osteolysis and implant failure. While titanium is traditionally considered bioinert, emerging evidence suggests that under certain conditions, even inert metals can induce adverse biological effects. Furthermore, this review emphasizes the role of oxidative stress, illustrating how metal ion release and systemic toxicity contribute to long-term health risks. It also uncovers the underappreciated genotoxic and cytotoxic effects of metal ions on cellular metabolism, shedding light on potential long-term repercussions. By integrating a rigorous methodological approach with an in-depth exploration of metal-induced biological responses, this paper offers a more nuanced perspective on the complex interplay between metal implants and human biology, advancing the discourse on implant safety and material innovation.

Keywords:
orthopaedic implants, toxicity, metals, biomaterials