Inconel-718 has received an extensive using in mold industry. The selective laser melting (SLM) is providing an ideal means for manufacturing mold insert with complex geometrical features and ...internal architecture. During the manufacturing of high quality mold inserts with conformal cooling channel, the parameters play a vital role in the SLM process. In the study, the Inconel-718 alloys were manufactured by SLM with 2×2mm2, 3×3mm2, 5×5mm2, and 7×7mm2 island scanning strategies. The microstructure, mechanical property, and residual stress were investigated by optical microscope, tensile test and Vickers micro-indentation, respectively. It can be found that the relative density increased with enlarging the island size; the results on the microstructure indicated that the cracks and more pores were detected in the 22-specimen; whilst the microstructures of all specimens were composed of fine dendritic grains, cellular, and columnar structures; the tensile testing suggested that the ultimate tensile strength and yield strength of all samples was similar; while the outcome of the residual stress showed that the value of residual stress was ranked in the following sequence: 22-specimen<55-specimen<77-specimen<33-specimen. Although the 22-specimen had lower residual stress compared with the other groups, the occurrence of cracks limited its processing application in SLM. Through integrated into account, the 55-scanning strategy is a promising candidate for manufacturing of mold inserts.
•Laser scanning strategies in selective laser melted Inconel-718 were studied.•The analysis of mechanical property and residual stress were proposed.•The island scanning strategy affected the formation of pores and cracks.
Selective Laser Melting (SLM) technology is effective for fabricating complex shape parts with superior strength and ductility. However, the high-temperature gradient and rapid solidification rate in ...the SLM process led to unstable material microstructure, which indicated an excellent strength and poor elongation of the SLM specimen. In order to achieve outstanding strength-plasticity matching, the influences of different solution temperatures (1000 °C, 1100 °C, and 1200 °C) on the evolution of phase and microstructure of Fe–22Cr–5Ni-0.26 N duplex stainless steel (DSS) fabricated by SLM were investigated. The results were then used to clarify the corresponding variations in mechanical properties of the specimens under tensile loading. The results revealed that the AS-SLM specimen showed high yield strength and poor elongation which was 1162.52 MPa and 4.97%. Solution treatment at 1000 °C can increase the elongation from 4.97% to 29.21% due to the two-phase structures recovered, grains refined, as well as eliminate dislocation and residual stress through recrystallization. As the temperature rose, the yield strength declined, while elongation remained almost unchanged. Except for elongation, the tensile strength, yield strength, and hardness were all higher than those of forged specimens. Therefore, solution treatment is an efficient strategy to improve the mechanical properties of the SLMFe-22Cr–5Ni-0.26 N DSS with excellent yield strength and plasticity.
In the study, the microstructure, mechanical property and metal release behavior of selective laser melted CoCrW alloys under different solution treatment conditions were systemically investigated to ...assess their potential use in orthopedic implants. The effects of the solution treatment on the microstructure, mechanical properties and metal release were systematically studied by OM, SEM, XRD, tensile test, and ICP-AES, respectively. The XRD indicated that during the solution treatment the alloy underwent the transformation of γ-fcc to ε-hcp phase; the ε-hcp phase nearly dominated in the alloy when treated at 1200°C following the water quenching; the results from OM, SEM showed that the microstructural change was occurred under different solution treatments; solution at 1150°C with furnace cooling contributed to the formation of larger precipitates at the grain boundary regions, while the size and number of the precipitates was decreased as heated above 1100°C with the water quenching; moreover, the diamond-like structure was invisible at higher solution temperature over 1150°C following water quenching; compared with the furnace cooling, the alloy quenched by water showed excellent mechanical properties and low amount of metal release; as the alloy heated at 1200°C, the mechanical properties of the alloy reached their optimum combination at UTS=1113.6MPa, 0.2%YS=639.5MPa, and E%=20.1%, whilst showed the lower total quantity of metal release. It is suggested that a proper solution treatment is an efficient strategy for improving the mechanical properties and corrosion resistance of As-SLM CoCrW alloy that show acceptable tensile ductility.
The electrochemical corrosion behaviors of as-SLMed CoCrW alloy after different heat treatments were investigated in 0.9% NaCl solution with and without the fluoride ions by open circuit potential ...(OCP), potentiodynamic polarization, electrochemical impedance measurements (EIS). The results showed that the SLMed CoCrW with a homogeneous structure experienced heat treated at 1150 °C followed by water quenching exhibited the better corrosion resistance to the electrolyte, whereas the alloy heat treated at 1150 °C followed by furnace cooling with a large amount of continuous blocky precipitates was susceptible to the corrosion. The XPS results indicated that the fluoride ions addition promoted the absorption of F−, Cl− and Na+ on the passive film. The fluoride ions slightly accelerated the corrosion of the SLMed CoCrW alloy by changing the composition of the passive film, thereby reducing the protectiveness of the film. Accordingly, a corrosion mechanism associated with the fluoride ion to the as-SLMed CoCrW alloy was proposed herein.
•The corrosion behaviors of SLMed CoCrW alloy with different heat treatments were studied.•A fine microstructure of SLMed CoCrW alloy exhibits good corrosion resistance.•The F− leads to formation of Cr(OH)3 and Cr-F or Cr-Cl complex in the passive film.
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•Adding the Cu led to the formation of Cr-enriched precipitates in the matrix.•The Cr7C3 precipitate in the CoCrMo-4Cu was partially coherent with Cu nanoparticle.•The Cr-enriched ...precipitates were the critical contributor to enhancing the tribology property.•The corrosion resistance of CoCrMo alloy was enhanced as the 2 and 3 wt% Cu added into CoCrMo alloy.
In this study, the cobalt-chromium-molybdenum (CoCrMo) alloys containing varying Cu contents (CCM-xCu, x = 0, 2, 3, 4 wt%) were fabricated via the selected laser melting (SLM) method. The influences of Cu content on tribological performance and corrosion resistance were investigated. The 2 and 3 wt% Cu contributed to inhibiting the generation of the HCP phase, whereas the inhibitory effect was quite limited at 4 wt% Cu. Notably, 4 wt% Cu led to the formation of Cr-enrich precipitates in the matrix, which was partially coherent with the Cu nanoparticle. The corrosion resistance of the CCM alloy was enhanced as the 2 and 3 wt% Cu added into the CCM alloy, contrarily, which deteriorated when Cu content reached 4 wt%. For the CCM-2Cu and CCM-3Cu, Cr-precipitates played a major role in enhancing the wear resistance, while the Cu lubrication effect working in coordination with Cr-precipitates determined that for the CCM-4Cu. This study was expected to achieve better tribology and corrosion properties of SLM-produced CCM alloys by tailoring microstructure through the Cu element.
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•The early bone ingrowth into the novel Co29Cr9W3Cu scaffold was investigated.•All scaffolds with different unit structures could favor the osteogenesis and angiogenesis in vtro.•A ...proper mismatch of elastic modulus between scaffold and bone may favor early bone ingrowth in time.
In this study, the Co29Cr9W3Cu porous scaffolds with different unit cell types including octahedron (OCT), face-centered cubic (FCC), and hexahedron (HCP) were fabricated by selective laser melting, aiming to reduce the stress shielding effect and promote the early bone ingrowth. The effect of pore size and unit cell types on the compressive stress and elastic modulus were investigated, and regulating pore size led to the compressive stress and elastic modulus ranging from 3.7 to 467 MPa and from 2.6 to 36.3 GPa, respectively. The in vitro results demonstrated that the ability to support the osteogenesis and angiogenesis was for the most part similar between the FCC-65, OCT-65, and HCP-65 scaffolds (porosity of 65%). After implantation in goats for 12 weeks, the FCC-65, OCT-65, and HCP-65 scaffolds showed sufficient results for guiding bone ingrowth, indicating good biocompatibility and osteointegration; interestingly, the scaffold with OCT unit cell structure offered the strongest ability to accelerate bone mineralization compared with the FCC-65, HCP-65 scaffold, possibly due to mechanical-adapted properties. The study was expected to offer the possibility of the SLM-produced Co29Cr9W3Cu scaffold to achieve osseointegration by guiding early bone ingrowth into the bone contact porous surface of the ankle joint.
Recently, selective laser melting (SLM) technology has been broadly used in medical application because it is suitable for the fabrication of personalized implants. However, it is well accepted that ...the parts produced by SLM with unique microstructure would affect the corrosion resistance, which may result in the release of metal ions and further induce peri-implantitis. In this work, self-developed Ti6Al4V3Cu gas-atomized powders with antibacterial property were fabricated for SLM technology. The differing heat treatments were applied to SLM-produced Ti6Al4V3Cu alloys to address the microstructure to improve the corrosion resistance. The microstructure of the Ti6Al4V3Cu alloys with heat treatment was investigated to insight into the relationship between evolved microstructure and their corrosion behavior. The corrosion behavior of the Ti6Al4V3Cu alloys was studied in terms of the electrochemical and static immersion test. The microstructural characterization depicted that the formation of the equilibrium structure with increasing the grain size and releasing residual stress was observed when elevated heat temperature. The corrosion test suggested that the Ti6Al4V3Cu alloys heated at 760 °C for 2 h ameliorated the corrosion resistance. The results indicated that a proper heat treatment is an efficient strategy for improving the corrosion resistance of Ti6Al4V3Cu alloys.
Metallic elemental powder mixture and pre-alloyed metallic powder are both frequently used powder feedstock in the additive manufacturing process. However, little research has been conducted to ...compare the corrosion behavior of selective laser melting (SLM) alloys, fabricated by pre-alloyed metallic powder and mixed metallic powder. Hence, it is important to investigate the corrosion behavior of SLMed alloys, as well as the corresponding cast ingot, with the aim to better understand the feasibility of designing new materials. In this work, the SLM-produced Ti6Al4V3Cu alloys were manufactured using a metallic elemental powder mixture and pre-alloyed metallic powder, respectively. The corrosion behavior of the different Ti6Al4V3Cu alloys was investigated in following electrochemical tests and ion release measurements. The results showed that the Ti6Al4V3Cu alloy prepared by pre-alloyed metallic powder showed better corrosion resistance than that produced from mixed metallic powder. Moreover, the SLM-produced Ti6Al4V3Cu alloys performed significantly better in corrosion resistance than the cast Ti6Al4V3Cu. The results are expected to achieve a better understanding of the feasibility of designing new materials using mixed powders, contributing to reducing development costs and cycles.
Microstructure, tribological property and corrosion resistance of orthopedic implant materials CoCrW-3 wt.% Cu fabricated by selective laser melting (SLM) process were systematically investigated ...with CoCrW as control. Equaxied γ-phase together with the inside {111} < 112 > type twin and platelet ε-phase was found in both the Cu-bearing and Cu-free alloys. Compared to the Cu-free alloy, the introduction of 3 wt.% Cu significantly increased the volume fraction of the ε-phase. In both alloys, the hardness of ε-phase zone was rather higher (~4 times) than that of γ-phase zone. The wear factor of 3 wt.% Cu-bearing alloy possessed smaller wear factor, although it had higher friction coefficient compared with Cu-free alloys. The ε-phase in the CoCr alloy would account for reducing both abrasive and fatigue wear. Moreover, the Cu-bearing alloy presented relatively higher corrosion potential E
corr
and lower corrosion current density I
corr
compared to the Cu-free alloy. Accordingly, 3 wt.% Cu addition plays a key role in enhancing the wear resistance and corrosion resistance of CoCrW alloys, which indicates that the SLM CoCrW-3Cu alloy is a promising personalized alternative for traditional biomedical implant materials.
Purpose
The aim of the study is to obtain dense Ni-free CoCrW parts fabricated by selective laser melting (SLM) technique for dental application.
Design/methodology/approach
The optimum of processing ...CoCrW powders was investigated by the varying laser scanning speeds between 200 and 1,500 mm/s with the other parameters fixed as constants. The investigations of density, phase, mechanical property and corrosion resistance were conducted.
Findings
It was found that a maximum relative density of 99.4 per cent was obtained with the preferable laser scanning speed of 700 mm/s; the outcome from the tensile test suggested that the 0.2 per cent yield strength of the specimen fabricated at 700 mm/s satisfied the type 5 criteria in ISO22764 for dental application, whereas the electrochemical test indicated that the specimens fabricated at 700 mm/s existed excellent corrosion resistance. The high precision dental denture could be fabricated by SLM.
Originality/value
In the study, the Ni-free CoCrW parts fabricated by SLM was investigated by the tensile and electrochemical tests. The yield strength, corrosion resistance and margin fit accuracy met requirements for dental application. It was considered that the speed of 700 mm/s with the laser powers of 95 W, the track width of 0.11 mm and the layer thickness of 25 μm are promising candidates for fabricating the CoCrW parts.
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