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This study reports the successful development of bioactive coatings on in-situ alloyed Ti-40Nb substrates fabricated via selective laser melting (SLM) using plasma electrolytic oxidation (PEO). Two electrolytes were employed for PEO processing: phosphate–silicate (PS) and phosphate–silicate–hydroxyapatite (PSHA). A comparative evaluation was performed to investigate the influence of electrolyte composition on surface morphology, corrosion resistance, and biological performance. The incorporation of hydroxyapatite (HAp) in the PSHA electrolyte significantly modified the coating structure, resulting in reduced porosity, increased surface roughness, and enhanced wettability. X-ray diffraction analysis confirmed the formation of TiO₂ (anatase and rutile) and Nb₂O₅ phases, with a higher rutile fraction observed in the HAp-incorporated coatings due to intensified plasma discharges. Electrochemical testing in simulated body fluid (SBF) demonstrated improved corrosion resistance for the HAp-containing samples, as evidenced by lower corrosion current density and passivation current values. In vitro assays with MC3T3 pre-osteoblast cells further revealed superior cell viability and proliferation on the HAp-incorporated coatings, attributed to the synergistic effects of roughened topography and the sustained release of bioactive ions. Overall, the PEO-modified Ti40Nb samples exhibited enhanced corrosion protection and cytocompatibility, underscoring their strong potential as next-generation Ti-based orthopedic implant materials.

Eggshells are a biowaste and potential bio-ceramic due to the major calcium carbonate (CaCO3) content, which offers bioactivity, bioresorbability, biocompatibility, and antibacterial properties. To benefit from the properties of the eggshell, this study explores the combined use of ceramic (eggshell) and ductile metal (CP-Ti as a hexagonal prism) as composites. A novel Ti-eggshell composite was fabricated by combining additive manufacturing and powder metallurgical routes. The novel Ti-eggshell composites were characterized for structural and microstructural analysis using X-ray diffraction and scanning electron microscopy. The hexagonal Ti structs deform marginally during composite manufacturing (minor variations in the struct dimensions may be observed) and the composites show the following compressive properties: yield strength of 123 ± 34 MPa and a Young's modulus of 47 ± 2 GPa within the range of natural human cortical bone. In addition, the Ti-eggshell composite offers non-cytotoxic and antibacterial behavior when tested with gram-negative-Pseudomonas. Aeruginosa and gram-positive-Staphylococcus. Aureus bacteria suggesting that such novel Ti-eggshell composites can be suitable members for bioimplant applications. © 2024 Elsevier Ltd and Techna Group S.r.l.

Ti-Nb alloy fabricated via selective laser melting (SLM) serves as a promising candidate for orthopedic implants due to its exceptional biocompatibility and ability to mitigate stress-shielding effects. However, processing of insitu alloyed Ti-Nb powder results in non-homogeneous microstructures and incomplete melting and diffusion of Nb hindering material homogeneity. In this study a laser remelting strategy was employed to enhance microstructural homogenization, Nb diffusion, and defect reduction. The effect of the cooling rate on the microstructure and mechanical properties of the resultant samples was explored. X-ray diffraction confirmed the presence of alpha ‘+beta phase in single and triple melted samples. Remelted samples exhibited superior microstructural uniformity, reduced porosity, larger grain size, and increased alpha ‘ martensite morphology as confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM analysis shows reduced dislocation density and twins upon remelting. The mechanical properties of the remelted sample maintained a desirable combination of low modulus and high strength with a hardness of 368 +/- 7 HV, yield strength of 820 +/- 35 MPa, compressive strength of 1480 +/- 50 MPa, and an elastic modulus of 33 +/- 3 GPa. This work proves laser remelting is an effective strategy for fabricating Ti-40Nb alloy from elemental powder contributing to the development of orthopedic implants.

This study investigates the microstructural, mechanical, corrosion, and biological behaviors of spark plasma sintered (SPS) zinc (Zn) samples for biomedical applications. The findings reveal that SPS significantly refines the grain structure of pure Zn compared to the conventional casting method. The SPS process, conducted at a lower sintering temperature of 300 degrees C and a high uniaxial pressure of 50 MPa, produces fine and uniform equiaxed grains with an average size of 19 mu m. The resulting Zn samples exhibit a calculated density of 7.1 g cc-1 due to complete densification. The sintering process disrupts the initial texture strength, and the uniform grain orientation achieved during SPS contributes to an isotropic microstructure, enhancing the mechanical properties. The compressive yield strength and ultimate strength of the SPS samples are 115 +/- 4 MPa and 191 +/- 6 MPa, respectively. The long-term biodegradation behavior of SPS Zn in simulated body fluid indicates controlled and gradual corrosion, supporting its potential for biodegradable implant applications, while potentiodynamic polarization analysis further confirms similar corrosion rates compared to cast Zn due to the formation of a stable corrosion product film. In vitro studies with MC3T3-E1 preosteoblast cells show healthy proliferation in culture media containing the degradation products of SPS Zn. Due to its unique microstructural, mechanical, and corrosion properties, along with its biocompatibility, SPS-processed Zn is a promising candidate for tissue engineering applications.

Titanium (Ti) and its alloys are widely used in orthopedic applications, including total hip and knee replacements, bone plates, and dental implants, because of their superior biocompatibility, bioactivity, corrosion resistance, and mechanical robustness. These alloys effectively overcome several limitations of conventional metallic implants, such as 316L stainless steel and Co-Cr alloys, particularly with respect to corrosion, fatigue performance, and biological response. However, dense Ti alloys possess a relatively high elastic modulus, which can cause stress shielding in load-bearing applications. This challenge has motivated significant research toward engineered porous Ti structures that exhibit a reduced and bone-matched modulus while preserving adequate mechanical integrity. This review provides a comprehensive examination of powder metallurgy and additive manufacturing approaches used to fabricate porous Ti and Ti-alloy scaffolds, including additive manufacturing and different powder metallurgy techniques. Processing routes are compared in terms of achievable porosity, pore size distribution, microstructural evolution, mechanical properties, and biological outcomes, with emphasis on the relationship between processing parameters, pore architecture, and functional performance. The reported findings indicate that optimized powder-metallurgy techniques can generate interconnected pores in the 100–500 ÎŒm range suitable for osseointegration while maintaining compressive strengths of 50–300 MPa, whereas additive manufacturing enables the precise control of hierarchical architectures but requires careful post-processing to remove adhered powder, stabilize microstructures, and ensure corrosion and wear resistance. In addition, this review integrates fundamental aspects of bone biology and bone implant interaction to contextualize the functional requirements of porous Ti scaffolds. © 2025 by the authors.

The present work is a comparative study on the TiC-430 L ferritic stainless steel (FSS) cermets manufactured via two powder metallurgical processes, namely, conventional spark plasma sintering (SPS) and metal additive manufacturing (AM) process (laser powder-bed fusion process (LPBF)/selective laser melting (SLM)). The rescanning strategy has been used to preheat and melt the powder bed with different laser parameters during the SLM process to suppress the presence of residual thermal stress leading to the fabrication of cermets without cracks. The as-fabricated SPS samples (95 %) show a relatively lower density than the SLM-built parts (~98 %). A study of their mechanical properties such as hardness, compressive strength, and fracture toughness was conducted and discussed in detail. Further, the corrosion behavior of the fabricated cermets parts was evaluated in 3.5 wt% NaCl. The SLM-prepared specimens reveal finer microstructures and better mechanical properties (compressive strength and fracture toughness) due to the presence of fine microstructure. Furthermore, the corrosion current density of TiC-430 L fss-based cermets fabricated by SLM is approximately 270 times lower than that of cermets parts fabricated by SPS, indicating excellent corrosion resistance. On the other hand, the hardness shows an opposite trend, where the SPS samples show the maximum hardness as compared to the SLM counterparts due to the presence of hard and coarse TiC particles along with some metallic carbides formed during the SPS process. The results reveal that AM processes not only can fabricate cermets with intricate shapes but can also fabricate them with improved mechanical and corrosion properties.

Two different grades, WC-20 vol.% Ni and WC-20 vol.% Co cemented carbides, respectively were systematically investigated concerning their microstructure, binder composition, and corrosion behavior. SEM-EBSD analysis verified that both grades have similar WC grain sizes (0.9–1.1 μm). AES analysis confirmed that the binder phase of the respective grade is an alloy of Ni-W and Co-W and that the concentration of W in the Ni- and Co-binder is 21 and 10 at. %, respectively. In synthetic mine water (SMW), the EIS behavior of WC-Ni(W) at the open circuit potential (OCP) conditions was studied for different exposure periods (up to 120 h). The EIS data fitting estimates low capacitance and high charge transfer resistance (Rct) values, which indicate that the passive film formed on WC-Ni(W) is thin and exhibits high corrosion resistance. At the OCP and potentiostatic-passive conditions, SEM investigations confirm the uncorroded microstructure of the WC-Ni(W). The AR-XPS studies confirmed the formation of an extremely thin (0.25 nm) WO3 passive film is responsible for the high corrosion resistance of WC-Ni(W), at OCP conditions. However, above the transpassive potential, the microstructure instability of WC-Ni(W) was observed, i.e., corroded morphology of both WC grains and Ni(W) binder. The electrochemical parameters, Rct, corrosion current density, and charge density values, confirmed that the WC-Ni(W) is a far better alternative than the WC-Co(W) for application in SMW.

This study deals with the tribological behavior of the TiC-430 L SS cermets fabricated via an additive manufacturing process such as laser powder bed fusion/selective laser melting. A gradient microstructure (finer and coarser morphology) can be observed in the fabricated parts due to SLM's complex thermal history. Using Rockwell indenter, single and multiple passes scratch tests have been performed as a function of applied load to study the wear mechanism of the binder and matrix phase. A surface 3D profilometer was used to analyze the scratch track variation in terms of scratch width and depth. Scanning Electron microscopy (SEM) analysis was performed on the scratched cermet parts to study the wear mechanism and microstructural analysis. It has been observed that the scratch hardness increases with increasing load and the same decreases with increasing the number of passes. Similarly, the coefficient of friction increases with increasing load. Cermets with complex microstructural features exhibit high wear resistance under low loads and for higher loads, multiple passes can lead to tribolayer formation.

CoCrFeMnNi high-entropy alloy (HEA)/AISI 316L stainless steel bimetals were additively fabricated using selective laser melting (SLM). The bimetal structure comprises three regions, i.e., CoCrFeMnNi-HEA, AISI 316L stainless steel, and an interface between CoCrFeMnNi-HEA, AISI 316L stainless steel. SLM processing results in the formation of columnar grains extending over many built layers epitaxially in a preferential growth direction. The Vickers microhardness ranges mainly between 250 and 275 HV0.5 in all three observed regions. In addition, only a marginal variation in tensile strength is observed between the CoCrFeMnNi-HEA, AISI 316L stainless steel, and the CoCrFeMnNi-HEA/AISI 316L stainless steel bimetal. The unique higher work hardening behavior of the CoCrFeMnNi-HEA prevents failure along the CoCrFeMnNi-HEA side in the bimetallic structure during plastic deformation. The CoCrFeMnNi-HEA shows higher pitting susceptibility than the AISI 316L stainless steel in the bimetallic structure due to its lower pitting potential. Further, the presence of pores and lack of fusion spots further decreases the pitting resistance of the CoCrFeMnNi-HEA. Hence, the bimetal is prone to more preferential corrosion attack along the CoCrFeMnNi-HEA side due to its anodic behavior and defects.