Full Densification Research Articles

Multifunctional performance of Ti2AlC MAX phase/2D braided alumina fiber laminates

AbstractThe processing and characterization of laminates based on Ti2AlC MAX phase, as matrix, and triaxial alumina braids, as reinforcing phase, are presented. Ti2AlC powders with a mean particle size below 1 µm are synthesized, while commercial 3M Nextel 610 alumina fibers are braided in a three‐stage process consisting of spooling, braiding with an angle of 0° and ±60° and the separation to single‐layer fabric. The laminates are processed by layer‐by‐layer stacking, where 3 two‐dimensional alumina braids are interleaved between Ti2AlC layers, followed by full densification using a Field‐Assisted Sintering Technology/Spark Plasma Sintering. The multifunctional response of the laminates, as well as for the monolithic Ti2AlC, is evaluated, in particular, the thermal and electrical conductivity, the oxidation resistance, and the mechanical response. The laminates exhibit an anisotropic thermal and electrical behavior, and an excellent oxidation resistance at 1200℃ in air for a week. A relatively lower characteristic biaxial strength and Weibull modulus (i.e., σ0 = 590 MPa and m = 9) for the laminate compared to the high values measured in the monolithic Ti2AlC (i.e., σ0 = 790 MPa and m = 29) indicates the need but also the potential of optimizing MAX‐phase layered structures for multifunctional performance.

Multimodal particle size distribution by mixing nanopowders for full densification of spark plasma sintered SiC ceramics

Highly pure free of additives fully dense SiC ceramics (>99 % theoretical density) were manufactured by Spark Plasma Sintering. The mixing of two initial nanopowders, exhibiting different average particle sizes, was favorable for densification, thanks to wider particle size distribution and modification of the powder rheological behavior. Furthermore, this mixing step lessened the cohesive and electrostatic behaviors of the initial powders, making it possible to reach densities higher than 99 % of the theoretical density, without exaggerated grain growth. In addition to promoting the densification, the mixing step enabled easier handling, facilitating the die filling process, and enhanced their compaction ability. Finally, fully dense SiC ceramics were obtained at 2100 °C without any dwell time. The produced ceramics exhibited an average Knoop hardness of 24 GPa (HK1), which is similar to the Hexoloy® SA reference. Notably, the Young's Modulus was slightly higher at 429 GPa versus the 404 GPa of the reference.

Influences of B4C content and particle size on the mechanical properties of hot pressed TiB2–B4C composites

ABSTRACT TiB2 ceramic has attracted many attentions due to its excellent performances both on mechanical and functional properties. However, it is still very difficult to obtain TiB2 bulks with full densification. Herein, TiB2–B4C composites were prepared via hot pressing at 1900°C under the pressure of 35 MPa with TiB2 and B4C as the raw materials. The influences of B4C content (0, 10 vol%, 20 vol% and 30 vol%) and particle size (0.50 µm, 3.12 µm and 7.09 µm) on the phase composition, relative density, microstructure and mechanical properties of TiB2–B4C composites were investigated. The using of 0.50 µm B4C brought more B2O3 which induced oriented growth of TiB2 grains and coarsened the obtained composites. When the raw B4C powders were 3.12 µm and 7.09 µm, the obtained composites with 20–30 vol% B4C could be fully densified. TiB2–30 vol% B4C composite prepared from 3.12 µm B4C powder resulted in the optimal mechanical properties. The bending strength, Vickers hardness, fracture toughness were 671 MPa, 27.93 GPa, and 3.91 MPa·m1/2, respectively. The excellent performance was attributed to its fine and homogenous microstructure.

Pressureless solid-state sintering of SiC ceramics with BN and C additives

ABSTRACT This study proposes BN as a new sintering aid for pressureless solid-state sintering of SiC ceramics. The full densification of SiC ceramics for 0.5–2.7 wt% BN addition showed the composition tolerance of the newly developed ceramics. The electrical resistivity decreased by an order of magnitude (107→106 Ω·cm) as BN content increased from ~0.5 to ~0.9 wt% because of the increased BN-derived B doping in the SiC lattice. A further increase in BN content had no significant effect on the electrical resistivity, which is attributed to the limited solubility of B in the SiC lattice. The thermal conductivity decreased with increasing BN content owing to increased phonon scattering at B-doped sites and the thermally insulating BN phase located at the grain boundaries. The fracture toughness increased with increasing BN content owing to interfacial debonding at the weak SiC-BN interfaces. However, intrinsically weak BN grains with low hardness were responsible for reduced flexural strength and hardness with increasing BN content.

Pressureless sinterability study of ZrB2–SiC composites containing hexagonal BN and phenolic resin additives

This research is dedicated to the role of different amounts of hexagonal BN (hBN: 0, 1.5, 3, and 4.5 wt%) on the pressureless sinterability of ZrB2–25 vol% SiC ceramics. Phenolic resin (5 wt%) with a carbon yield of ~40 % was incorporated as a binder to the powder mixtures and after initial cold pressing, the final sintering process was performed at 1900 °C for 100 min in a vacuum furnace. The as-sintered specimens were characterized by X-ray diffractometry, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results disclosed that the incorporation of 1.5 wt% hBN could increase the relative density to ~92%, while the sample with zero hBN content just reached ~81% of full densification. Appropriate hBN content not only facilitated the particle rearrangement during the cold pressing, but also removed the harmful oxide impurities during the final sintering. Nevertheless, the addition of higher amounts of hBN remarkably lessened the densification because of more delamination of the non-reacted hBN flakes and release and entrapment of more gaseous by-products induced by the reacted hBN phases.

Effect of Temperature and Holding Time on Zirconia Toughened Alumina (ZTA) Prepared by Two-Stage Sintering

The microstructure and mechanical properties of Zirconia Toughened Alumina (ZTA) produced via two-stage sintering at various sintering temperature of T1 and T2 in addition to effect of various holding time were investigated. T1 temperature was set between the range of 1400°C to 1500°C with a heating rate of 20°C/min. The samples were then sintered at T2 ranging from 1350°C to 1400°C followed by various holding time between 2 hours to 12 hours. The sintered samples’ microstructural properties, bulk density, hardness (Vickers hardness), elastic modulus (Young’s modulus) and fracture toughness (K1C) were then determined. Compared to standard holding time of two-stage sintering which is 12 hours, results show that ZTA produced via two-stage sintering with shorter holding time of 4 hours with T1 set at 1500°C and T2 of 1450°C are capable of achieving full densification. In addition, the same sample were also able to achieve hardness up to 19 GPa, Young’s modulus of 390 GPa and fracture toughness of 6.1 MPam1/2. The improvement in mechanical properties can be mainly attributed to the absent of surface diffusion at T2 above 1400°C and also presence of Y-TZP which contributed to lower grain growth due to the pinning effect.

Influence of the Total Porosity on the Properties of Sintered Materials—A Review

Porosity is a characteristic present in most sintered materials, full densification only being achieved in special cases. For some sintered materials, porosity is indeed a desired characteristic, serving for the intended application of the material. In any case, the porosity present in materials can have a strong effect on some of their properties, both structural and functional. In this paper, some of the expressions proposed to describe the influence of the total porosity on the effective properties of sintered materials are examined. Moreover, a universal expression (with two fitting parameters) valid to satisfactorily represent all the analysed behaviours is proposed. One of these parameters can be assimilated to the tap porosity of the powders used to manufacture the material. The properties examined were elastic moduli, ultimate strength, thermal and electrical conductivities, magnetic characteristics, and other properties directly related to these ones. The study is valid for sintered materials, both metallic and ceramic, with a homogeneous and non-texturised microstructure.

A current-controlled flash sintering processing leading to dense and fine-grained typical multi-element ZnO varistor ceramics

Comparing to conventional sintering, the densification, microstructure and electric properties of typical multi-element ZnO-Bi2O3-based varistor ceramics on different constant furnace temperatures (850–1000 °C) were studied at electric field of 250 V/cm by flash sintering. The flash-sintered specimens of near full densification could be obtained within 35 s, which had finer grain size and more homogenous microstructure. The effect of different limited current on densification was investigated in flash sintering process. The results showed the relative densities of specimens from 89.9% to 92.0%, 95.5% while limited current increased from 1.0 A to 1.5 A, 2.0 A. The 950 °C flash-sintered specimen with the relative density of 98.0% had the highest threshold voltage of 656 V/mm with the nonlinear coefficient of 41.9. The dielectric loss of flash-sintered specimens had the value lower than 0.2. Thus, typical multi-element ZnO varistor ceramics could show uniform microstructure and excellent electric properties by constant furnace temperature flash sintering.

Ultrashort-time liquid phase sintering of high-performance fine-grain tungsten heavy alloys by laser additive manufacturing

Liquid phase sintering (LPS) is a proven technique for preparing large-size tungsten heavy alloys (WHAs). However, for densification, this processing requires that the matrix of WHAs keeps melting for a long time, which simultaneously causes W grain coarsening that degenerates the performance. This work develops a novel ultrashort-time LPS method to form bulk high-performance fine-grain WHAs based on the principle of laser additive manufacturing (LAM). During LAM, the high-entropy alloy matrix (Al0.5Cr0.9FeNi2.5V0.2) and W powders were fed simultaneously but only the matrix was melted by laser and most W particles remained solid, and the melted matrix rapidly solidified with laser moving away, producing an ultrashort-time LPS processing in the melt pool, i.e., laser ultrashort-time liquid phase sintering (LULPS). The extreme short dwell time in liquid (~1/10,000 of conventional LPS) can effectively suppress W grain growth, obtaining a small size of 1/3 of the size in LPS WHAs. Meanwhile, strong convection in the melt pool of LULPS enables a nearly full densification in such a short sintering time. Compared with LPS WHAs, the LULPS fine-grain WHAs present a 42% higher yield strength, as well as an enhanced susceptibility to adiabatic shear banding (ASB) that is important for strong armor-piercing capability, indicating that LULPS can be a promising pathway for forming high-performance WHAs that surpass those prepared by conventional LPS.

Microstructure and Mechanical Properties of High Relative Density γ-TiAl Alloy Using Irregular Pre-Alloyed Powder

Preparing high relative density γ-TiAl alloy by pressure-less sintering at low-cost has always been a challenge. Therefore, a new kind of non-spherical pre-alloyed TiAl powder was prepared by the reaction of TiH2 powder and Al powder at 800 °C to fabricate high-density Ti-48Al alloy via pressure-less sintering. The oxygen content was controlled to below 1800 ppm by using coarse Al powder (~120 μm). The sintered densities ranged from 92.1% to 97.5% with sintering temperature varying from 1300 °C to 1450 °C. The microstructure of the sintered compact was greatly influenced by the sintering temperature. The as-sintered samples had a near-γ structure at 1350 °C, a duplex structure at 1400 °C, and a nearly lamellar structure at 1450 °C. To achieve full densification, non-capsule hot isostatic pressing was performed on the 1350 °C and 1400 °C sintered samples. As a result, high compressive strengths of 2241 MPa and 1931MPa were obtained, which were higher than the existing Ti-48Al alloys.

Processing and oxidation response of Cr2AlC MAX-phase composites containing ceramic fibers

Three different ceramic matrix composites (CMCs) were produced using Cr2AlC as a matrix, and carbon, SiC and Al2O3 short fibers as a secondary phase. Cr2AlC powders were synthesized by solid-state reaction, followed by mixing with the fibers, and full densification using a field-assisted sintering technique. Of the three different fiber types, Carbon fibers reacted strongly with Cr2AlC, while the reaction with SiC fibers was more limited and alumina fibers didn’t show any reaction. Oxidation tests of the monolithic Cr2AlC and the composites were performed by thermogravimetric analysis. An alumina layer formed at 1000 ​°C on every sample, well attached and worked as a good oxidation barrier. Under realistic conditions using a burner rig for cyclic oxidation at 1200 ​°C for 500 cycles, the oxidation resistance of the alumina fiber CMC is good, as no defects or degradation are visible and the alumina layer is well attached.

Synthesis and microstructure evolution of β‐Sialon fibers/barium aluminosilicate (BAS) glass‐ceramic matrix composite with enhanced mechanical properties

AbstractDense Sialon fibers/barium aluminosilicate (BAS) matrix self‐reinforced composite was synthesized by one‐step method without applying pressure before or during sintering process. In this work, BAS matrix and internal Sialon fibers were synthesized successfully by directly sintering precursor powders at 1400°C for 4 h. The BAS is not only introduced as a structural matrix material, but also as an effective liquid phase sintering aid to attain full densification bulk sample. The results show that the diameter of fibers is about 100–200 nm, and the quantity of the fibers can be changed with different temperatures. The obtained Sialon fibers/BAS matrix composites exhibit better toughness due to fiber bridging, crack deflection, and pullout. The sample with 3.5 wt% carbon content has maximum value of flexural strength (74.5 ± 3.5 MPa) and fracture toughness (3.2 ± 0.20 MPa·m1/2). The growth of the Sialon fibers follows a vapor‐liquid‐solid (V‐L‐S) mechanism. These findings featured with a green and simple preparation process provide a facile strategy to design and fabricate the bulk ceramic matrix composites in complex shapes and different sizes.

Phase analysis, mechanical properties and in vitro bioactivity of graphene nanoplatelet-reinforced silicon nitride-calcium phosphate composites

ABSTRACT The aim of this study is to produce highly dense Si3N4 based composites with good mechanical properties and bioactivity. Si3N4 ceramics without using sintering aids, Si3N4-HA and Si3N4-HA-GNP based composites have been produced by spark plasma sintering (SPS) at temperatures of 1525–1550°C. The effect of reinforcement type and content on the densification behavior, phase analysis, microstructural development, mechanical properties, and in-vitro bioactivity behavior of Si3N4 were systematically investigated. Monolithic Si3N4 that contains a high amount of β-Si3N4 phase (~87 wt%) was produced by nearly full densification (~99%). Hydroxyapatite (HA) was used as a starting powder during the preparation of binary and triple composites to provide bioactivity to Si3N4, and after sintering, HA transformed into tricalcium phosphate (β-TCP and α-TCP) polymorphs. The incorporation of GNPs had a positive effect on the stability of β-TCP phases at higher sintering temperatures. The improvement in indentation fracture toughness of the samples with GNP reinforcement was mainly attributable to pull-out and crack deflection mechanisms. In-vitro bioactivity of GNP added composites enhanced with increasing α-TCP content. More calcium phosphate-based particle formation was observed in Si3N4-HA-GNP composites compared to the Si3N4-HA.

Effects of 211 and 413 ordering on the corrosion behavior of V-Al-C MAX phases prepared by spark plasma sintering

In the present study, two V-Al-C based MAX phases, i.e., V2AlC and V4AlC3 having two types of ordering were successfully manufactured by spark plasma sintering and the corrosion behavior of sintered samples was evaluated. Al, V and C metal powders were mixed with the desired molar ratios by a mixer mill, and sintered at 1300 °C. The relative density calculation revealed almost full densification for both prepared MAX phases. The measurements of mechanical properties showed a low increase in bending strength and Vickers hardness of V4AlC3 compared to V2AlC MAX phase. Evaluation of corrosion behavior of developed MAX phases was carried out in 6.5 M HCl solution using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests. Corrosion current density and corrosion potential of V2AlC (5.3 ± 0.21 μA/cm2 and -0.451 ± 0.01 V, respectively), and V4AlC3 (1.07 ± 0.22 μA/cm2 and -0.091 ± 0.02 V, respectively) were measured and no passivation behavior was observed in their potentiodynamic polarization curves. However, EIS tests at open circuit potential confirmed more corrosion resistance of V4AlC3compared to V2AlC. These tests also revealed the active dissolution of MAX phases in 6.5 M HCl solution at anodic potential of +0.1 V, while the impedance values of V4AlC3 were larger than those of V2AlC. Microstructural investigation revealed the preferential dissolution of V2AlC phase in grain boundaries after corrosion test. Moreover, the layered structure of V2C MXenes was observed in some regions. After corrosion test, V4C3 MXene layers had larger thickness compared to V2AlC. It was found that V4AlC3 with higher amount of Al2O3 and thicker layers has more corrosion resistance than V2AlC MAX phase.

Preparation of bulk Cu-W interpenetrating-phase composites by liquid metal dealloying

Copper-Tungsten (Cu-W) composites are promising materials for electrical and thermal applications. Manufacturing the desired Cu-W composites with full densification and a homogenous microstructure remains difficult, however, owing to the lack of mutual solubility, poor wettability, and the large difference in melting temperature between W and Cu. Here, a fully dense homogenous bulk Cu-W composite with a three-dimensional bicontinuous interpenetrating-phase architecture is fabricated by liquid metal dealloying (LMD) method, which involves immersing the Ni-W alloy in a molten metal Cu bath. The microstructure evolution mechanisms and the dealloying kinetics from a Ni-W precursor alloy to Cu-W composite are investigated. The synthesized Cu-W composite structure showed morphology variations depending on the dealloying time. The coarsening mechanism of the W ligaments during dealloying were analyzed based on curvature-driven surface smoothening and Rayleigh instability controlled ligament pinch-off process.

SHS Synthesis, SPS Densification and Mechanical Properties of Nanometric Tungsten

Recent studies have shown that low grain sizes are favorable to improve ductility and machinability in tungsten, as well as a resistance to ablation and spallation, which are key properties for the use of this material in a thermonuclear fusion environment (Tokamaks such as ITER). However, as one of the possible incidents during Tokamak operation is the leakage of air or water from the cooling system inside the chamber, resulting in the so-called loss of vacuum accident (LOVA), extensive oxidation may arise on tungsten components, and the use of an alloy with improved oxidation resistance is therefore highly desirable. As current production routes are not suitable for the fabrication of bulk nanostructured tungsten or tungsten alloys samples, we have proposed a new methodology based on powder metallurgy, including the powder synthesis, the densification procedure, and preliminary mechanical testing, which was successfully applied to pure tungsten. A similar study is hereby presented on tungsten-chromium alloys with up to 6 wt.% Cr. Results show that full tungsten densification may be obtained by SPS at a temperature lower than 1600 °C. The resulting morphology strongly depends on the amount of the alloying element, presenting a possible second phase of chromium oxide, but always keeps a partial nanostructure inherited from the synthesized powders. Such microstructure had previously been identified as being favorable to the use of these materials in fusion environments and for improved mechanical properties, including hardness, yield strength and ductility, all of which is confirmed by the present study.

Mechanical properties of ceramic composites based on ZrO2 co-stabilized by Y2O3–CeO2 reinforced with Al2O3 platelets for dental implants

ObjectivesThe objective of this work was the development and characterization of a ceramic composite based on (Ce,Y)-TZP/Al2O3 aiming an application on dental implants, comparing it with conventional monolithic 3Y-TZP ceramics, currently used for the same type of application. MethodsCeramic samples, 3Y-TZP (n = 40) and (Ce,Y)-TZP/Al2O3 (n = 40), were sintered at 1500 °C - 2h and characterized by relative density, X-Ray diffraction (XRD) and microstructure. Then, the samples of both materials were divided into two groups: 1) samples with original (as sintered) surfaces; 2) samples with conditioned, polished, surfaces. All samples were submitted to hydrothermal degradation tests, on an autoclave (134 °C - 2 bar), for 10 h in artificial saliva. The degraded samples were characterized by XRD and the polished group were also characterized by their elastic moduli, Vickers hardness and fracture toughness (Vickers indentation method). Both groups were also submitted to a flexural strength test, 3B–P testing, for which the data were interpreted using Weibull statistics. ResultsAll sintered specimens presented nearly full densification. After the hydrothermal degradation tests, 3Y-TZP samples presented 16.4% of monoclinic (m)-ZrO2 phase while the composite samples withheld 100% of tetragonal (t)-ZrO2 phase. Both materials presented equiaxial ZrO2 grains with an average size of 0.48 ± 0.17 μm and 0.75 ± 0.22 μm, respectively, for the monolithic and composite ceramics. In the composites, is observed the presence of well distributed Al2O3 grains on the ZrO2 matrix, in two distinct morphologies: equiaxial grains and platelets. The composites (Ce,Y)-TZP/Al2O3 presented average values of elastic moduli, Vickers hardness and fracture toughness of 228.3 ± 6.5 GPa, 1427 ± 46 HV e 11.3 ± 0.4 MPa m1/2, respectively. An inversely proportional relationship is observed between the roughness and the bending strength, since the 3Y-TZP samples presented a average strength of 860.7 ± 81 MPa (as-sintered) and 965.4 ± 93 MPa (polished) while the (Ce,Y)-TZP/Al2O3 composites presented average strength of 810.6 ± 147 MPa (as-sintered) and 952.6 ± 88 MPa (polished). ConclusionsThe composites (Ce,Y)-TZP/Al2O3 showed high resistance to degradation in saliva and adequate properties for use as dental implants. Values of flexural strength (>950 MPa) and Weibull modulus (m > 10) were similar to the conventional 3Y-TZP ceramics. Moreover, its hardness, elastic modulus and fracture toughness were higher than those obtained for 3Y-TZP. The expressive values of KIC obtained for (Ce,Y)-TZP/Al2O3 composites are results of association of different toughening mechanisms acting simultaneously in the material.

Cold sintering of as-dried nanostructured calcium hydroxyapatite without using additives

A novel low-temperature densification method of nanocrystalline calcium hydroxyapatite (HAp) at a temperature as low as 200 °C with no liquid additives is investigated. To understand the underlying mechanism of the low-temperature sintering of hydroxyapatite, two types of lab-synthesized nanocrystalline HAp, dried (110 °C, 12 h) and calcined (1000 °C, 2 h), were subjected to cold sintering conditions (200 °C, 500 MPa) and compared thoroughly. The dried samples were found to be nanocrystalline, enveloped by an amorphous shell, whereas the calcined samples were fully crystalline, as confirmed by X-ray diffraction, transmission electron microscopy, and solid-state nuclear magnetic resonance techniques. A relative density of 98.8% was achieved for the dried samples; however, the calcined samples could not be sintered. This indicates a clear dependence of densification on the surface chemistry of the nanocrystals involving rearrangement and dehydration of the amorphous layer present on the surface of the nanocrystals under the influence of applied pressure and temperature. Moreover, the calcined sample, which had a fully developed crystalline structure, did not undergo sintering, even with the use of added water. Therefore, it is demonstrated that wet-precipitated and dried nanocrystalline HAp can be cold-sintered to full densification for applications in biomedical materials or radioactive waste immobilization of volatile radionuclides at a considerably low temperature, without the addition of sintering aids.

Spark plasma sintering and dry sliding-wear of ZrC-16.7 vol.% Co cemented carbides

The densifiability by spark plasma sintering (SPS) and the dry sliding-wear behaviour of novel cemented carbides based on micrometre-sized ZrC with 16.7 vol.% Co binder (ZrC–Co), compositionally equivalent to the typical WC–10 wt%Co but with ZrC in place of WC, were investigated. Firstly, detailed analysis of both the densification and the shrinkage-rate curves registered during SPS (at 50 MPa) showed that ~1275 °C is the onset SPS temperature for liquid-phase sintering, and ~1600 °C that of full densification. Hardness measurements by Vickers indentation tests confirmed the gradual densification with increasing SPS temperature up to 1600 °C, a condition yielding an extra-coarse-grained (~7–8 μm grain size), ultrahard (~18.2 ± 0.3 GPa) ZrC–Co cemented carbide that is also sufficiently tough (~6.1 ± 0.2 MPa m1/2). And secondly, pin-on-disk tribological tests (at both 20 N for 1000 m and 40 N for 2000 m) and subsequent characterization of the worn surfaces indicated that, under sliding contact, these ZrC–Co cemented carbides wear essentially by two-body abrasion dominated by plastic deformation. Wear increases with increasing severity of the contact conditions, but is nonetheless mild due to the high hardness of these ZrC–Co cemented carbides and to the formation of discontinuous oxide tribolayers.

High-performance Ti-6Al-4V with graded microstructure and superior properties fabricated by powder feeding underwater laser metal deposition

Abstract It is challenging to apply laser metal deposition (LMD) in underwater environment to realize on-site repair of marine equipment due to the potential impact of water. In the present work, we report an innovative underwater repair technique termed underwater laser metal deposition (ULMD) which can overcome the challenges. This new technique renders both technical and theoretical advancements from the following aspects: (1) A special in-house designed drainage nozzle was integrated with the laser cladding head to create local dry cavity which ensured the successful manufacturing of titanium alloy Ti-6Al-4V in underwater environment; (2) Unique microstructure formation/evolution mechanisms have been revealed for the ULMD process, which significantly differ from those of the in-air LMD process; (3) The hydrogen content has been well controlled during ULMD, which can effectively prevent the formation of hydrogen-induced cracks; (4) The mechanical properties of the ULMD Ti-6Al-4V parts were equal or even better than that fabricated by in-air LMD or SLM technique. In the meantime, a systematically parametric study was performed for this new technique and the experimental results showed that a high laser power (1600 W), a reasonable scanning velocity (800 mm/min) and a cross-hatching strategy were essential for achieving minimum metallurgical defects and full densification, which can provide very helpful guidance for the future research in this area. This research work opens a new avenue which makes underwater 3D-printing an applicable tool when coping with the fabrication and repair of customized components or complex shape parts in underwater environment.