316L Matrix Research Articles

Mechanical properties of additively manufactured ultrafine grain stainless steel-titanium boride (SS–TiB2) nanocomposites

Stainless-steel, particularly the 316L alloy, is extensively utilized across diverse industrial sectors. Nonetheless, its inherent limitation of low yield strength poses a significant challenge. In this study, we propose a novel method to address this limitation by incorporating trace quantities of TiB2 nanoparticles into the 316L matrix. The methodology involves a combination of low-energy ball milling for the preparation of the powder feedstock, followed by selective laser melting (SLM) for the fabrication of nanocomposites. The resulting stainless-steel nanocomposite exhibits a nearly-full dense structure characterized by the uniform dispersion of TiB2 nanoparticles (30–40 nm in diameter) within the matrix grain interiors and at grain boundaries. This leads to a substantial refinement in the matrix grain and a remarkable enhancement in mechanical properties. Specifically, the incorporation of 3 vol% TiB2 nanoparticles results in substantial enhancements in tensile yield strength (90.5 %), microhardness (81.4 %), ultimate strength (78.03 %) and bulk modulus (75.2 %) at room temperature compared to plain SLMed stainless-steel. This notable enhancement arises from the uniform dispersion of TiB2 nanoparticles and grain refinement, achieved without discernible processing defects such as agglomeration or interface microcracks. These findings offer a promising avenue for enhancing the mechanical characteristics of stainless-steel-based nanocomposites, thereby expanding their applicability in demanding engineering environments.

The strengthening mechanism of mechanical and tribological properties of TiC-reinforced 316L matrix composites fabricated by selective laser melting

Selective laser melting (SLM) has been proved to be a promising additive manufacturing technique to fabricate high-performance metal matrix composites (MMCs) with unique microstructures. In this study, TiC-reinforced 316 L MMCs were successfully prepared by SLM. The effects of TiC addition on the microstructure evolution, mechanical properties and tribological behavior were systematically investigated to study the strengthening mechanism. The TiC/316 L MMCs fabricated by SLM exhibited a high relative density of over 99.6% and were close to full density. The TiC particles are effectively bonded with the 316 L matrix, serving as a means of dispersion strengthening. In addition, the grains were significantly refined, and the dislocation density was greatly enhanced with the addition of TiC particles, which reinforce the strength of the material. Tensile tests show that the tensile strength of TiC/316 L MMCs increased by 49.9% from 707 to 1060 MPa and yield strength increased by 44.2% from 543 to 783 MPa with 4 wt% TiC. Besides, the tribological behavior of TiC/316 L MMCs was much superior to the pure 316 L. The findings provide a new perspective on ceramic particles reinforced stainless steel MMCs with tailored microstructure and excellence performance.

Microstructural evolution, mechanical properties and tribological behavior of SiC reinforced 316L matrix composites fabricated by additive manufacturing

Selective laser melting (SLM) has been proved to be a promising additive manufacturing technique for production of high-performance metal matrix composites (MMCs) with unique microstructures. In this study, the SiC- reinforced 316L MMCs were prepared by SLM and the effects of SiC addition on the densification, microstructure evolution, mechanical properties and tribological behavior were systematically investigated. The SiC/316L MMCs fabricated by SLM were close to full density with high relative density over than 99.7%. The grains were significantly refined, and dislocation density was greatly enhanced with the addition of SiC particles. Tensile tests show that tensile strength of the specimens increased by 81.8% from 707 to 1285 MPa and yield strength increased by 72.7% from 543 to 938 MPa with the addition of SiC. In addition, the tribological behavior of MMCs with SiC addition are much superior to the pure 316L. The underlying strengthening mechanisms are discussed. The findings provide a new perspective on ceramic particles reinforced stainless steel MMCs with unique microstructure and excellence performance.

Direct evidence of melting and decomposition of TiC particles in laser powder bed fusion processed 316L-TiC composite

Recent advancements have shown the effectiveness of strengthening 316L with TiC particles addition through the laser powder bed fusion (LPBF) process. However, the question remains whether TiC undergoes decomposition into Ti and C atoms, primarily because of the challenges associated with measuring C at low concentrations. In this study, we employed atom probe tomography (APT) to provide evidence of decomposition by observing the presence of Ti and C atoms in the 316L matrix. The fast cooling rate of the LPBF process results in the supersaturation of Ti and C in the 316L matrix. Adding 3 wt% TiC particles increased the yield strength of LPBF-processed 316L from 599 MPa to 832 MPa. The subsequent annealing treatment resulted in the formation of more TiC nanoparticles as a result of precipitation from the supersaturated Ti and C in the 316L matrix. Consequently, the yield strength was further enhanced to 959 MPa after annealing at 700 °C for 1 h. This study marks the first direct demonstration of the decomposition of TiC in metal matrix composites.

Laser powder bed fusion in situ alloying of AISI 316L-2.5%Cu alloy: microstructure and mechanical properties evolution

This work investigates the effects of copper addition on the microstructure and mechanical properties of AISI 316L austenitic stainless steel fabricated by the laser powder bed fusion (L-PBF) method. The outcomes reveal that the copper atom dissolves into iron and forms a complete austenitic structure under the condition of the L-PBF process. Microstructural observations demonstrate that the microstructure of the new alloy is characterised by columnar grains consisting of finer cellular structures, as compared to the as-built AISI 316L. The appearance of such a finer sub-structure could be originated from the effect of copper on the cooling rate during the L-PBF process. The energy-dispersive X-ray spectroscopy maps indicate that the distribution of copper in the AISI 316L matrix is homogeneous, and no significant segregation of elements in the matrix is revealed. The results of the tensile tests show that the ultimate tensile strength of AISI 316L-Cu alloy is 558 MPa, whereas the yield strength value and the tensile elongation are 510 MPa and 30.4%, respectively. Two mechanisms of solid solution strengthening, and refinement of cell sizes improve the mechanical properties of AISI316L-Cu alloy compared with AISI 316L one. The microscale fractography of the fracture surface shows ductile fracture with massive dimple networks and brittle fracture with a quasi-cleavage plane, which may indicate the melt pool boundary. All these results confirm that the development of new alloys following the in situ alloying approach is economical and reliable.

Fabrication and structural, physical, and nuclear radiation shielding properties for Oxide Dispersion-Strengthened (ODS) alloys through Erbium (III) oxide, Samarium (III) oxide, and Praseodymium (III) oxide into 316L matrix

We report a comprehensive investigation on customization process of Oxide Dispersion-Strengthened alloys through Sm2O3, Pr2O3, and Er2O3 incorporation into 316L stainless steel matrix in terms of a desired enhancement in structural, physical, and nuclear radiation shielding properties. Oxide powders are incorporated into 316L stainless steel powder all with the same purity of 99.5%. These were Erbium oxide (Er2O3), Praseodymium oxide (Pr2O3), and Samarium oxide (Sm2O3). First, X-Ray diffraction and Scanning Electron Microscope/Energy-dispersive X-ray spectroscopy analyses are conducted in order to investigate their physical and structural properties. Next, two different experimental setups are employed using a133Ba and 241Am/Be sources for the measurements of gamma-ray and neutron transmission properties of Oxide Dispersion-Strengthened alloys. The maximum density increment is achieved through Er2O3 compared to other reinforced oxides. The detector counting value reached its minimum level when a 5% Er2O3 oxide dispersion was introduced into the 316L SS matrix. Similarly, the most significant degree of photon absorption, the highest values of mass attenuation coefficient, lowest half value layer, and most effective atomic number, were all attained by the same sample. Based on the findings derived from the investigation, it can be concluded that incorporating Er2O3 oxide into 316L steel can be considered as a viable option in terms of enhancing the critical properties of Oxide Dispersion-Strengthened alloys for extreme conditions such as nuclear reactors and other similar fields, where the behavioral attributes of the utilized materials are at utmost importance.

Embedding of Y3Al5O12:Ce within 316L stainless steel parts by laser powder bed fusion as an efficient luminescent sensor

Transition to circular economy requires the production of sustainable and eco-designed materials that help to reduce environmental impacts of metallic components. The development of sensing layers providing luminescent tracking functionalities is a potential method for extending the service life of metallic parts. In this study, incorporation of luminescent Ce3+ doped yttrium aluminum garnet (YAG:Ce) within a stainless steel 316L (SS316L) matrix has been achieved for the first time by laser powder bed fusion (L-PBF). Embedding of phosphor particles was successfully carried out on a selected area of the 3D printed sample. Despite harsh processing conditions of L-PBF, luminescent emission was detected by optical spectroscopy. Microstructure and chemical composition of the incorporation zone were investigated in order to better understand optical properties. The precipitated particles exhibit new optical features, arising from the modification of the luminescent host lattice and the intricate interactions with the metal matrix.

The multifunctional performance of the laser powder bed fusion 316L stainless steel matrix composite reinforced with the CNT-ZrO2 nanohybrid

The effects of CNT-ZrO2 nanohybrid reinforcement on the microstructure features, mechanical properties, wear behavior, and corrosion resistance of laser powder bed fusion (LPBF) stainless steel 316L (SS 316L) were analyzed. X-ray diffraction, scanning electron microscopy, Raman analysis, tensile, pin-on-disk, and potentiodynamic polarization tests were conducted to determine the function of the CNT-ZrO2 nanohybrid reinforcement in enhancing the properties of the fabricated LPBF SS 316L matrix composite. The hardness, tensile properties, wear behavior, and corrosion resistance of the LPBF composites with various wt.% of the CNT-ZrO2 nanohybrid were compared with those of the unreinforced SS 316L and the SS 316L matrix composite containing detached CNTs and ZrO2 nanoparticles. The outcomes demonstrated a synergistic influence between the CNT and ZrO2 in an integrated nanosystem in improvement in the hardness, strength, wear behavior, and corrosion resistance of prepared composites.

Microstructure and mechanical performance of low-cost biomedical-grade Titanium-316L alloy

A 316L stainless steel (SS) alloy was developed with 1, 3, and 5 vol% titanium (Ti) reinforcement using the powder injection molding route, representing a low-cost option for biomedical implants. The investigation encompassed 1300 °C, 1350 °C, and 1380 °C sintering temperatures to ascertain the optimal physical and mechanical properties. Both sintering temperature and Ti influenced sintered density, and Ti mitigated the deleterious effects of residual carbon. At higher sintering temperatures, carbon and silicon tended to migrate and accumulate at the brink of Ti, leading to the formation of intermetallic compounds and increased brittleness. Dispersed Ti particles within the 316L matrix acted as nucleation sites and enhanced solid solubility with improved density. An astounding 96.11 % sintered density was achieved at 3 vol% Ti sample sintered at 1380 °C. During the tensile test, 5 vol% Ti at 1380 °C exhibited a low modulus of 58.9 GPa, which is highly desirable for orthopedic implant application. The XRD, SEM, tensile test, and nano-indentation results collectively provide evidence of beta-titanium formation during the sintering process. Conversely, the sample incorporating 3 vol% titanium, sintered at 1380 °C, demonstrated a balanced performance, showcasing 432.94 ± 12.8 MPa ultimate tensile strength, 3.06 ± 0.17 % elongation, 74.2 GPa modulus, and 322 MPa and 423 MPa 0.2 % offset flexural and compressive yield strengths, respectively. Notably, an improvised wear resistance test underscored its aptitude for sliding wear resistance, solidifying its potential as a promising candidate for biomedical implants.

Investigation of Microstructure and Mechanical Properties of Layered Material Produced by Adding Al2O3 to 316L Stainless Steel

This study developed new advanced composite materials consisting of functional grading of 316L and Al2O3 specially designed for potential biomedical applications. Mechanical properties were characterized by tensile testing, and microstructural properties by optical microscope, scanning electron microscope (SEM), and Energy Dispersive X-Ray (EDX) analyses. The uniform mixture in the material, up to 40% by weight of Al2O3, is uniformly distributed in the 316L matrix that shows disintegration. Then, samples with 2, 3, 4, and 5 layers were produced in functionally graded 6, 7, 8, and 9 material types, respectively. The layer thicknesses were formed with an average of 900 µm. The results show that new composite materials can be produced functionally using 316L and Al2O3 in a layered manner. As a result of the mechanical experiments, it has been observed that the tensile strength of the layered composite structures remains within the range of 91–191 MPa, depending on the layer type. It has been observed that the elongation varies between 3.16 and 12.46%. According to these results, the materials obtained are considered suitable for use as an alternative prosthetic material in biomedical applications. The tensile strength, % elongation of the Composition 7, and yield strength of functionally graded (316 + (316L-10 Al2O3) + (316L-20 Al2O3) + (316L-30 Al2O3)) material are 123 megapascals (MPa), 7.3%, and 111MPa, respectively, and according to the literature, the mechanical strength of human bone is very close to this composition properties.

On the melt pool dynamic of voxel-controlled metal matrix composites via hybrid additive manufacturing: Laser powder bed fusion and ink-jetting

In this study, the effect of the addition of reinforcement nanoparticles to the 316L matrix by adopting ex-situ and in-situ method (drop on demand jetting) to produce 316L/Al2O3 nanocomposite was investigated. In the ex-situ method, the Al2O3 nanoparticles (NPs) were lightly mixed with 316L powder and processed by laser powder bed fusion. In the in-situ method, an ethanol-based ink containing Al13 nanoclusters (NCs) was added to 316L powder and then processed by laser. Both ex-situ and in-situ method produced nanocomposites with Al-Si-Mn-O-enriched precipitations within the 316L matrix. The addition of NPs/NCs to the 316L matrix, altered the geometrical characteristic of the single-track melt pools. At the same laser power, with increasing the amount of Al2O3 NPs and Al13 NCs the melt pool deepened due to reduced thermal conductivity and prolonged liquid presence. As a result, 316L/1 wt% Al13 NCs deposited single track showed larger grains in comparison to 316L single track. At a high laser power of 150 W, the Marangoni flow and the buoyancy force caused the nanoparticles to agglomerate and float to the top surface of tracks; therefore, the wt% fraction of precipitation was drastically reduced due to the loss of Al. The 316L/Al2O3 NPs and 316L/Al13 NCs exhibited the microhardness of 285 ± 13 HV and 293 ± 7 HV, respectively, higher than the deposited 316L single track, 265 ± 15 HV. Lastly, a hybrid LPBF+ink-jet printer was adopted to selectively change the composition of different zones by adding Al13 NCs ink to 316L and producing a voxel-controlled metal matrix composite.

Effect on Wear Performance of ZrO2 Amount of 316L Stainless Steel Matrix Composites Produced by a Mechanical Alloying Method

Abstract This study investigated the wear performances of ZrO2 reinforced 316L stainless steel matrix composite materials. The 316L matrix was mechanically alloyed by adding three different amounts (1 wt%, 2 wt%, and 3 wt%) of ZrO2 for 60 min. Mechanically alloyed powders were shaped through a uniaxial hydraulic press under 800 MPa pressure, and thus, green compacts in Ø12 × 6 mm dimensions were produced. The green compacts produced were sintered at 1300 °C in a vacuum environment of 10−6 mbar for 2 h. Sintered composites were characterized by hardness and density measurements and microstructure studies. The wear tests were carried out under ASTM G99-05 standards through a pin-on-disc wear test device, exerting three different loads (10 N, 20 N, and 30 N) and using four different sliding distances (500 m, 1000 m, 1500 m, and 2000 m). As a result of the studies, it was observed that the reinforcement material (ZrO2), added to the matrix, was positioned at the grain boundaries. As the amount of reinforcement within the matrix increased, the hardness of the composites increased while their densities decreased. In the wear test results, on the other hand, the increase in the amount of reinforcement decreased the weight loss. As for the wear surfaces, the abrasive wear mechanism was dominant.

Evaluation of the corrosion resistance of spark plasma sintered stainless steel 316L matrix composites with zirconium diboride in sulfuric acid

Evaluation of the corrosion resistance of spark plasma sintered stainless steel 316L matrix composites with zirconium diboride in sulfuric acid

Effect of nano TiC on microstructure and microhardness of composite additive manufacturing 316L stainless steel

The lower surface hardness limits the further application of 316 L stainless steel. In this study, selective laser melting (SLM)/laser metal deposition (LMD) composite additive manufacturing technology was used to prepare five kinds of 316L-nano-TiC cermet strengthening layers on the surface of 316L stainless steel, and to study the effect of nano-TiC particle content on the microstructure and the influence of microhardness. Use Laser microscope, scanning electron microscope (SEM), X-ray diffractometer (XRD) to analyze the structure, element distribution and phase composition of the strengthening layer. The hardness of the strengthened layer was analyzed using a Vickers micro-hardness tester. The study found that the composite SLM/LMD formed samples changed continuously from LMD forming to SLM forming, showing good metallurgical bonding. Diffusion of TiC particles was observed in the SLM strengthening layer, and TiC phase was detected in the strengthening layer. Compared with the 316L matrix, the microhardness of the strengthened layer is significantly improved. When 50 wt% TiC is added, the average hardness of the strengthened layer is 1.9 times that of the 316L matrix, and the highest is 408.9 HV. The results of this study show that the strengthening layer manufactured by composite additive materials can effectively improve the hardness of the 316L stainless steel matrix. As the content of nano-TiC in the preset powder increases, the microhardness of the strengthening layer first increases and then decreases, and the hardness of the 50wt% TiC strengthening layer is the highest. There are distributed nano-TiC particles in the structure of the strengthening layer, and the distribution of nano-TiC particles in the 50wt% TiC strengthening layer is more uniform than other samples. This research provides a new reference for the strengthening of 316L stainless steel through SLM/LMD composite additive manufacturing technology and the addition of nano-TiC particles.

Sintered 316L/Cu/h-BN composites

Sintered 316L/h-BN composites show high potential as self-lubricating materials, which can be applied as moving parts where lube oils and greases are not applicable and inaccessible for maintenance. The past production of such composites by sintering, faced two problems. Firstly - interaction between 316L matrix and h-BN resulting in loss of h-BN content and its lubricity. And secondly - poor 316L matrix integrity. This work employed two approaches to solve such problems. The first approach was the use of nitrogen-containing atmosphere for sintering, to retard 316L matrix and h-BN interaction. And the second approach, was copper addition to promote sintering of 316L powder particles. Sintered self-lubricating 316L/Cu/h-BN composites were produced from mixtures of 3 different 316L/Cu matrices (made by additions of 2.0, 4.0 and 6.0 wt.% copper powder to 316L powder) and 15 vol.% of h-BN powder. Green compacts of powder mixtures were sintered under cracked ammonia (75 vol.% hydrogen + 25 vol. % nitrogen) at 1300°C for 60 minutes. The sintered composites were cooled in a Linn high temperature sintering furnace. It was found that copper additions led to the decrease of densities of sintered 316L/Cu/h-BN composites, compared to that of sintered 316L/h-BN composite, due to porosity left behind by copper powder melting and dissolution. Tensile strengths of sintered 316L/Cu/h-BN composites were improved when copper contents were 4 and 6 wt.%. There was no intergranular phase, the evidence of 316L matrix and h-BN interaction in all experimental sintered composites. Microstructural observation by scanning electron microscopy (SEM) also revealed that h-BN flakes still existed in pores of sintered composites. The unreacted h-BN flakes are expected to provide lubricity of sintered composites.

Design, fabrication and comprehensive properties of the novel thermal neutron shielding Gd/316L composites

The constitutive equation of the 155/157Gd areal density and thermal neutron shielding rate was established by Monte Carlo N Particle Transport Code (MCNP) and used to design the novel Gd/316L stainless steel thermal neutron shielding materials. When the 155/157Gd areal density is greater than 0.01 g/cm2, the thermal neutron absorption rate of the Gd/316L composite reaches approximately 99%. The novel thermal neutron shielding materials with different Gd (1 wt.%, - 5 wt.%,) contents were prepared at 950 °C by spark plasma sintering. The transition layer composed of FeNi3, GdNi, and Gd3Ni can be formed during the sintering process. Meanwhile, the mechanical properties of Gd/316L composites decrease with the increase of the Gd content. In H3BO3 solution, pitting corrosion and galvanic corrosion occur at the interface between Gd and 316L matrix.

Additively manufactured SiC-reinforced stainless steel with excellent strength and wear resistance

Abstract Additive manufacturing enables in-situ alloying of multi-component materials for the development of novel and high-performance materials. Here laser powder bed fusion (LPBF) of SiC-reinforced 316L stainless steels metallic matrix composites (MMCs) for improved strength and wear resistance were investigated. The densification behaviour, microstructural evolution, crystallographic orientation and properties of the LPBF-processed MMCs with different SiC contents were systematically investigated. The formation mechanisms of pores and cracks are discussed. Microstructural observations reveal that the microstructure changes from equiaxed to dendritic with increasing SiC are related to the different temperature gradient and solidification rates. The SiC addition affects crystallographic orientation and causes grain refinement to 316L. In addition, micron SiC particles are refined to nano-scale after laser processing, which induces massive dislocations in the 316L matrix. The strength and tribological properties of 316L are significantly improved by SiC addition, in which the 9 vol% SiC reinforced MMC reaches a high tensile strength of about 1.3 GPa, together with a low wear rate of 0.77 × 10−5 mm3/Nm. The achieved strength and wear resistance are at the highest level among literature, and the underlying strengthening mechanisms are elucidated.

Selective laser melting of dispersed TiC particles strengthened 316L stainless steel

316L austenitic stainless steel has a wide range of industrial applications. However, one of the major drawbacks is its low yield strength (170–300 MPa in annealed state). We report a method to strengthen 316L by adding 1 wt% and 3 wt% micron-sized TiC particles using low energy ball milling for the powder feedstock preparation followed by selective laser melting (SLM). The TiC particles were observed to be uniformly dispersed and well bonded to the 316L matrix after SLM. The 316L-TiC composites obtained were close to full density and the austenite grains were significantly refined with the addition of TiC particles. Tensile tests show that adding 1 wt% and 3 wt% TiC particles leads to a significantly increased yield strength (660 MPa and 832 MPa) and UTS (856 MPa and 1032 MPa) and maintains the good ductility (55% and 29% elongation). These findings offer a new perspective on the strengthening of 316L stainless steel

Dry-sliding wear of the 316L/h-BN composites produced under crack ammonia atmosphere

Wear is one of different problems in mechanical failures of moving components. When a component encounters friction force on its surface, crack initiation tends to occur and wear follows crack propagation. Thus, the moving parts of automobiles should have proper wear resistance for long-time services, in addition to having high strength and hardness for heavy load operation. A self-lubricating material with compromised tribological and mechanical properties is important for some moving components. In this work, self-lubricating composites, metal matrix composites embedded with a solid lubricant, made from 316L stainless steel powder mixed with different hexagonal boron nitride (h-BN) contents of 10%, 15% and 20% by volume. The mixed powders were compacted into green parts (according with MPIF Standard 42) with density of 6.5 g·cm-3. Then, the green parts were sintered at 1100, 1150, 1200, 1250 and 1300°C under cracked ammonia (75% H2+25% N2) atmosphere for 60 min. The experimental results revealed that increases of hardness and strength sintered 316L matrix by reduction of pore amount and size were due to the increase of sintering temperature. However, the increase of h-BN content resulted in increase of pore amount and size. Additions of h-BN content up to 20 vol. % reduced friction coefficient of the sintered composites. At sintering temperatures of equal to and higher than 1200°C, h-BN did not react with 316L stainless steel powders to form intergranular boride phase. The sintered composites produced under the maximum experimental sintering temperature of 1300°C showed low specific wear rate.

155/157Gd areal density: A model for design and fabrication of Gd2O3/316L novel neutron shielding composites

The Monte Carlo N-Particle Code were used to design a novel Gd2O3/316L stainless steel neutron shielding composites (Gd2O3/316L NSCs). And the constitutive equation between the 155/157Gd areal density and the neutron shielding rate was established by MCNP. When the areal density of 155/157Gd is larger than 0.01 g/cm2, the thermal neutron shielding rate of the composites reaches 99%. The NSCs with three weight fractions (1.5 wt%, 2.5 wt%, and 4.5 wt% Gd2O3) were successfully fabricated by spark plasma sintering. And Gd2O3 particles evenly distributed in 316L matrix. The main phases of the composite are austenite (γ-Fe) and Gd2O3, and in addition Fe2Gd and Gd2Ni17 are present at the interface of Gd2O3 and 316L matrix particles. The debonding of the Gd2O3 particles is the main cause of material fracture.