Search for: All records

3D printing (3DP) technologies have transformed the processing of advanced ceramics for small‐scale and custom designs during the past three decades. Simple and complex parts are designed and manufactured using 3DP technologies for structural, piezoelectric, and biomedical applications. Manufacturing simple or complex geometries or one‐of‐a‐kind components without part‐specific tooling saves significant time and creates new applications for advanced ceramic materials. Although development and innovations in 3DP of ceramics are far behind compared with metals or polymers, with the availability of different commercial machines in recent years for 3DP of ceramics, exponential growth is expected in this field in the coming decade. This article details various 3DP technologies for advanced ceramic materials, their advantages and challenges for manufacturing parts for various applications, and perspectives on future directions. We envision this work will be helpful to advanced ceramic researchers in industry and academia who are using different 3DP processes in the coming days.

 

Bimetallic wire arc additive manufacturing (AM) has traditionally been limited to depositions characterized by single planar interfaces. This study demonstrates a more complex radial interface concept, with in situ mechanical interlocking and as-built properties suggesting a prestressed compressive effect. A 308 L stainless core is surrounded by a mild steel casing, incrementally maintaining the interface throughout the Z-direction. A small difference in the thermal expansion coefficient between these steels creates residual stresses at their interface. X-ray diffraction analysis confirms phase purity and microstructural characterization reveals columnar grain growth independent of layer transitions. Hardness values are consistent with thermal dissipation characteristics, and the compressive strength of the bimetallic structures shows a 33% to 42% improvement over monolithic controls. Our results demonstrate that biomimetic radial bimetallic variation is feasible with improved mechanical response over monolithic compositions, providing a basis for advanced structural design and implementation using arc-based metal AM.

 

In order to investigate the in‐space in situ resource utilization, directed energy deposition (DED)‐based additive manufacturing (AM) has been utilized to process Martian regolith—Ti6Al4V (Ti64) composites. Here we investigated the processability of depositing 5, 10, and 100 wt% of Martian regolith premixed with Ti6Al4V using laser‐based DED, analyzing the printed structure via X‐ray diffraction, Vicker's microhardness, scanning electron microscopic imaging, and wear characteristics utilizing an abrasive water jet cutter to simulate abrasive environments on the Martian surface. The results indicate that the surface roughness and hardness of the composites increase with respect to the Martian regolith’ weight percentage due to in situ ceramic reinforcement. For instance, i5‐wt% addition of Martian regolith increased the Vicker's microhardness from 366 ± 6 HV_0.2for as‐printed Ti64 to 730 ± 27 HV_0.2while maintaining similar abrasive wear performance as Ti6Al4V. The results point toward laser‐based AM for fabricating Ti64—Martian regolith composites with comparable properties. The study also reveals promising results in limiting the mass burden for future space missions, resulting in cheaper and easier launches.

 

Directed energy deposition (DED) was used to produce niobium carbide (NbC)‐reinforced Ti6Al4V (Ti64) metal–matrix‐composite (MMC) structures. The objective was to improve upon Ti64's wear and oxidation resistance. The characterization techniques consisted of scanning electron microscopy (SEM), backscattered electron (BSE) imaging, energy‐dispersive X‐ray spectroscopy (EDS), X‐ray diffraction analysis (XRD), thermogravimetric analysis (TGA), Vickers micro‐ and nanoindentation‐derived hardness, as well as tribological testing at varying normal loads. DED produced compositions were of Ti64, Ti64 + 5 wt.% NbC (5NbC), and Ti64 + 10 wt.% NbC (10NbC). Electron micrographs revealed crack‐ and delamination‐free structures. Tribological analysis revealed a 25.1% reduction in specific wear rate. XRD and EDS results indicated the presence of a Ti‐Nb solid solution. It was deduced that the NbC particles coupled with the Ti‐Nb solid solution aided in increasing Ti64's resistance to plastic shear as the superficial microstructure remained unchanged compared to pure Ti64. Additionally, TGA displayed a reduction in total oxidation mass gain and suppressed oxidation kinetics to parabolic behavior with increased NbC. Application‐based composite structures with site‐specific mechanical properties were fabricated in the form of a composite cylinder, gear and compositionally graded cylinder. The graded cylinder displayed a 0%–45%NbC presence—end‐to‐end—equating to a hardness increase from 161.6 ± 4.0HV_0.2to 1055.9 ± 157.4HV_0.2.

 

Balancing strength and ductility is crucial for structural materials, yet often presents a paradoxical challenge. This research focuses on crafting a unique bimetallic structure, combining non-magnetic, stainless steel 316L (SS316L) with limited strength but enhanced ductility and magnetic, martensitic 17-4 PH with higher strength but lower ductility. Utilizing a powder-based laser-directed energy deposition (L-DED) system, two vertical bimetallic configurations (SS316L/17-4 PH) and a radial bimetallic structure (SS316L core encased in 17-4 PH) were fabricated. Monolithic SS316L, 17-4 PH, and a 50% SS316L/50% 17-4 PH mixture were printed. The printed samples' phase, microstructure, room temperature mechanical properties, and fracture morphology were examined in as-printed conditions. Bimetallic samples exhibited both phases, with a smooth grain transition at the interface. Radial bimetallic samples demonstrated higher mechanical strength than other compositions, except 17-4 PH. These findings showcase the potential of the L-DED approach for creating functional components with tailored mechanical properties. 

Stainless steel 316L (SS316L) is widely used in fracture management devices. However, SS316L does not offer any bacterial infection resistance and can cause metal-ion sensitivity due to Ni-ions' presence. 17-4PH can emerge as a promising substitute due to the intrinsic antibacterial properties of copper, a 75% reduction in nickel content, and superior mechanical properties. SS316L and 17-4 PH were manufactured using laser-directed energy deposition (LDED). 17-4PH specimens surpassed the compressive strength of SS316L by over 150%. A static magnetic field was generated in 17-4 PH specimens to understand in vitro bone cell-material interactions. In vitro human fetal osteoblast cell culture and bacterial inhibition study using Staphylococcus aureus and Pseudomonas aeruginosa were carried out on these specimens with SS316L as control and as-processed and magnetized 17-4 PH as treatments. Results demonstrated that magnetized 17-4 PH exhibited 25% enhancement in hFOB proliferation and 70% reduction in bacterial colonization compared to SS316L. 

The demand for advanced materials has driven innovation in titanium alloy design, particularly in the aerospace, automotive, and biomedical sectors. Additive manufacturing (AM) enables the construction of multi-material structures, offering potential improvements in mechanical properties such as wear resistance and high-temperature capabilities, thus extending the service life of components such as Ti6Al4V. Directed energy deposition (DED)-based metal AM was used to manufacture radial multi-material structures with a Ti6Al4V (Ti64) core and a Ti6Al4V-5 wt.% B4C composite outer layer. X-ray diffraction analysis and microstructural observation suggest that distinct B4C particles are strongly attached to the Ti6Al4V matrix. The addition of B4C increased the average hardness from 313 HV for Ti6Al4V to 538 HV for the composites. The addition of 5 wt.% B4C in Ti6Al4V increased the average compressive yield strength (YS) to 1440 MPa from 972 MPa for the control Ti6Al4V, i.e., >48% increase without any significant change in the elastic modulus. The radial multi-material structures did not exhibit any changes in the compressive modulus compared to Ti6Al4V but displayed an increase in the average compressive YS to 1422 MPa, i.e., >45% higher compared to Ti6Al4V. Microstructural characterization revealed a smooth transition from the pure Ti6Al4V at the core to the Ti64-B4C composite outer layer. No interfacial failure was observed during compressive deformation, indicating a strong metallurgical bonding during multi-material radial composite processing. Our results demonstrated that a significant improvement in mechanical properties can be achieved in one AM build operation through designing innovative multi-material structures using DED-based AM.

 

Powder contamination during laser powder bed fusion is a critical concern for the quality assurance of parts. Herein, we studied the effect of Inconel 718 contamination on the properties of printed Ti6Al4V, two commonly printed alloys. Contaminated parts exhibited visual and microstructural defects, and a mere 0.5wt% IN718 contamination resulted in a 43% reduction in plastic strain without noticing surface-level cracking. Further contamination of 2.5 wt% IN718 promotes surface cracking that renders the material unable to deform plastically, highlighting the importance of proper powder handling and the detrimental effects that even small amounts of contaminants can have on AM-produced components. 

Directed energy deposition (DED)-based additive manufacturing (AM) was employed to fabricate three distinct bimetallic compositions to understand the role interface for the deformation behavior of bimetallic structures under compressive loading. Commercially pure titanium (CP Ti) with a hexagonal closed packed (HCP) structure, nickel (Ni) with a face-centered cubic (FCC), and tantalum (Ta) with a body-centered cubic (BCC) structure were selected to understand the deformation behavior within the pure metals and damage accumulation at the bimetallic interface. By incorporating the combination of these materials, such as Ni-Ti, Ni-Ta, and Ta-Ti, we aimed to manufacture layered-base polycrystalline composite structures with FCC-HCP, FCC-BCC, and BCC-HCP crystal unit cells, respectively. In Ni-Ti and Ni-Ta bimetallic structures, it was determined that deformation is controlled by the Ni region, where the highest deflection occurs when Ni bulges out and makes lateral stress at the interface, resulting in crack initiation, propagation, and failure of the structure. Structural edges were found to experience the highest deformation, prompting grain inclination towards the <111> crystal orientation, resulting in a favorable orientation for dislocation slip and a higher Taylor factor. However, strong interfacial bonding and similar Young's modulus between Ta and Ti altered the deformation mechanisms to twinning formation in the Ti region and observed buckling of the entire structure without significant failure at the interface. 

In this study, we measured the tensile, compression, and fatigue behavior of additively manufactured Ti3Al2V as a function of build orientation. Ti3Al2V alloy was prepared by mixing commercially pure titanium and Ti6Al4V in 1:1 wt. ratio. Laser powder bed fusion-based additive manufacturing technique was used to fabricate the samples. Tensile tests resulted in an ultimate strength of 989 ± 8 MPa for Ti3Al2V. Ti6Al4V 90° orientation samples showed a compressive yield strength of 1178 ± 33 MPa and that for Ti3Al2V 90° orientation samples were 968 ± 24 MPa. By varying the build orientation to account for anisotropy, Ti32 45° and Ti32 0° samples displayed almost similar compressive yield strength values of 1071 ± 16 and 1051 ± 18 MPa, respectively, which were higher than that of Ti32 90° sample. Fatigue loading revealed an endurance limit (10 million cycles) of 250 MPa for Ti6Al4V and of 219 MPa for Ti3Al2V built at 90° orientation. The effect of the build orientation was significant under fatigue loading; Ti3Al2V built at 45° and 0° orientations displayed endurance limits of 387.5 MPa and 512 MPa, respectively; more than two-fold increment in endurance limit was observed. In conclusion, the superior attributes of Ti3Al2V alloy over Ti6Al4V alloy, as demonstrated in this study, justify its potential in load-bearing applications, particularly for use in orthopedic devices.