Wrought Substrate Research Articles

Effect of hot-wire method on microstructure and mechanical properties of wire arc additive repaired superalloy

This study shows that the hot wire is an effective way to reduce the amount of undesirable Laves phase during the repair of 718Plus components, which are detrimental to the mechanical properties. The complex relationship between microstructure and hotwire was studied in detail. Five damaged components were repaired by depositing the melted 718Plus wire onto the wrought substrate using directed energy deposition-arc (DED-arc). A finite element model was used to provide clues for the thermal process analysis. The hot-wire method enhanced the cooling rate of the molten pool and suppressed the remelting behaviour of secondary dendritic arms (SDA) in the reheated zone. The resultant microstructure contained refined dendrites with more obvious SDA, which allows the production of tiny reticular Nb-rich liquid spots between dendrites during final solidification stage. These spots beyond a threshold of Nb could cause eutectic reaction, leading to the morphologic transformation from long-stripped to granular Laves phase and a lower volume fraction. Moreover, the hot-wire method hindered the dynamic precipitation of γ' phase due to the shortened precipitation time, which was responsible for the inferior mechanical properties. The heat-treatment re-optimized the precipitation of γ' phase and further dissolved Laves phase to release more Nb for γ' phase, which leads to the improvement of strength about 10 %.

Exploring mechanical behavior at interfaces of laser powder bed fusion (LPBF) deposits on wrought Inconel 718: an indentation-based approach

PurposeThis study used an indentation-based mechanical testing framework for the mechanical characterization of laser powder bed fusion (LPBF) processed Inconel 718 on a wrought Inconel 718 substrate. The purpose of the paper is to investigate the effectiveness of the indentation-based approach for localized mechanical evaluation.Design/methodology/approachThe LPBF-processed wrought substrate was sectioned into three sections for microstructural and mechanical characterization. A 3D heat source model was used for the thermal analysis of the interface region. The developed interface region is probed using the Knoop hardness indenter in different orientations to determine the textural anisotropy and mechanical behavior of the region.FindingsLPBF process develops a melted interface zone (MIZ) at the deposition-substrate interface. The MIZ exhibited a coarse grain structure region along with a larger primary dendritic arm spacing (PDAS), signifying a slower cooling rate. FE modeling of the LPBF process reveals heat accumulation in the substrate along with intrinsic heat treatment (IHT) induced due to layer-wise processing. The obtained yield locus shows strong anisotropy in the deposition region, whereas reduced anisotropy with a nearly uniform ellipse locus for the MIZ regions. This reduced anisotropy is attributable to IHT and heat accumulation in the substrate.Originality/valueAn alternative localized mechanical characterization tool has been investigated in this work. The approach proved sensitive to thermal variations during LPBF processing in an isolated region which extends its suitability to variable geometry parts. Moreover, the approach could serve as a screening tool for parts made from dissimilar metals.

Fatigue and delamination of 6061 aluminum cold spray on a similar wrought substrate

Fatigue crack growth and fracture of a thick 6061 aluminum cold spray coating on 6061-T6 aluminum substrate were studied through in-situ observation of fatigue crack growth through the coating to the interface in notched four-point bend samples. Mode I cracking was observed through the coating before delamination at the substrate. Crack tip strain fields during the delamination event were plotted with DIC. Interfacial steady-state strain energy release rates were measured using the bimaterial four-point bend solutions by Charalambides. The interfacial crack primarily spread cleanly along the coating/substrate interface, with a post-fracture surface morphology containing a wavy structure with an amplitude on the same order of magnitude as the cold spray particle diameters. The in-situ video of crack propagation and coating-substrate delamination provides lessons for improving the coating-substrate interfacial toughness and thus expands use cases for structural cold spray applications

Inconel 718 Hybrid Laser-Based Directed Energy Deposition and Wrought Component Characterization through Small Punch Tests

The combination of wrought materials and laser-based directed energy deposition (DED-LB) is being increasingly used for manufacturing new and repairing old or damaged components in several industries. Aerospace components made of Inconel 718 featuring small-thickness DED-LB buildups are a remarkable example of such a combination due to the high added value it brings. Despite that these are usually critical components, the miniature testing methods to assess the local mechanical properties in the buildup area are not fully developed. This work contributes to this miniature testing development with an improvement of the small punch testing (SPT) technique for measuring the mechanical properties of the weld line between the DED-LB and the wrought substrate. A new criterion for weld line positioning in the SPT specimens is proposed and applied on samples of hybrid wrought/DED-LB Inconel 718. The results of positioning the weld line at the necking site of the SPT specimen show that the proposed approach is valid for assessing the properties of the transition zone between the wrought and additive states. For the specific conditions tested and taking the wrought material as a reference, the strength of the Inconel 718 drops 10% in the weld line and 20% in the buildup.

Microstructure and fracture toughness of laser wire deposited Ti-6Al-4V

In this paper, the microstructure, and mechanical properties of Ti-6Al-4V fabricated through Laser Directed Energy Deposition (L-DED) process are investigated and discussed. Deposited coupons were produced on Ti-6Al-4V wrought substrate using Ti-6Al-4V ELI grade wire with the laser wire deposition (LWD) process. Characterization efforts led to the evaluation of the microstructure, hardness, tensile behavior, and fatigue crack growth resistance of the build-up alloy. Microstructure of the deposit consists of columnar prior β grains and basket-weave α/β phase mixture. The size of the alpha laths is measured as 1.2 ± 0.3 µm and 0.8 ± 0.2 µm in the banded zone and band-free zone, respectively. Hardness of the deposited block is found to be uniform and ranging between 321 and 323 Hv. Tensile and fatigue crack growth properties of the deposited block were evaluated in various orientations. Tensile specimens loaded in the deposition direction exhibited 824 MPa and 930 MPa for yield and ultimate tensile strength, respectively. Tensile specimens loaded in the build direction exhibited 782 MPa and 907 MPa for yield and ultimate tensile strength, respectively. The analysis reveal that the tensile properties of the deposited material match the strength requirements for ASTM F1108 Cast Ti-6Al-4V. However, they fell just below the AMS 4911P Wrought Ti-6Al-4V standard. Fatigue Crack Growth Rate tests were conducted for three directions: parallel to the deposition direction, parallel to the build direction and at 45° of the deposition direction. No significant differences in crack growth properties were observed between the different orientations with average crack initiation near threshold (ΔKth) and the fracture toughness (Kc) value of 3.6 MPa√m and 69 MPa√m, respectively. The crack propagation properties are similar to cast & wrought materials.

Anisotropic dynamic compression response of an ultra-high strength steel fabricated by laser hybrid additive manufacturing

Directed energy deposition (DED) is a technological innovation revolutionizing in-situ repair, hybrid manufacturing, and multi-material integration manufacturing, characterized by microstructural heterogeneity on a macro-scale. However, the overall performance of these DED-fabricated components under dynamic loading, particularly along different directions, remains uncharted. This work explores the anisotropic dynamic compression response of an ultra-high strength steel, namely 35CrMnSiA steel, fabricated using DED on a wrought substrate. The laser hybrid additive manufactured samples were subjected to split Hopkinson pressure bar testing along different directions. The results show the following: 1) hybrid manufactured 35CrMnSiA steel has an anisotropic dynamic compression response due to the mismatched properties of each subzone induced by microstructural heterogeneity, 2) low-strength DED part shows higher strain under compression along the build direction but behaves similarly to the wrought material when compressed along the transverse direction, 3) intergranular void/crack is the primary damage mechanism, cracks preferred formed in wrought substrate due to the martensite with poor plastic dissipation ability, 4) when the interface is subjected to parallel directional impact loads, the strain mismatch between the two side subzones leads to interface separation. This study provides comprehensive understanding of the dynamic behavior of DED-fabricated components with heterogenous microstructure, and new insight into demanding tailored strategies to ensure consistent and predictable behavior under various loading conditions.

Exploring How LPBF process parameters impact the interface characteristics of LPBF Inconel 718 deposited on Inconel 718 wrought substrates

This work investigates the interface properties of LPBF Inconel 718 deposited on Inconel 718 wrought substrates fabricated using the laser powder bed fusion (LPBF) technique. The as-printed (S1, S2, S3, and S4) samples were characterized using optical microscopy (OM),scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and micro-hardness techniques.The samples showed the development of a melted interface zone (MIZ) at the wrought substrate-deposition interface for all processing conditions. The developed interface showed a dendritic grain structure, signifying the remelting of the wrought substrate followed by rapid solidification. The MIZ thickness increased with an increase in laser power and scan speed (28.5 % increase in the MIZ thickness with a ∼ 12 % increase in normalized enthalpy). The assessment of the MIZ showed a high-quality interface. However, with an increase in scanning speed, the density of the MIZ decreases owing to increased porosity and lack-of-fusion (LOF) defects. The S1 condition (250 W and 850 mm/s) resulted in a highly dense part with no visible porosity, LOF defects, and a high relative density (∼99.9 %) in the MIZ region. The S4 condition showed the presence of large porosities and LOF defects at the deposition-MIZ interface, signifying an inferior bond between the deposition and substrate. The microstructural characterization of the LPBF-processed and MIZ region showed an increase in the primary dendritic arm spacing (PDAS) with increasing laser power due to a reduced cooling rate. The micro-hardness characterization of the sample shows a decrease in the hardness of the MIZ attributed to the dissolution of strengthening phases due to remelting. The present work outcome demonstrates the effectiveness of the proposed methodology for manufacturing high-quality parts using LPBF technology.

Investigation on microstructure evolution of hybrid manufactured TC17 titanium alloy during cyclic deformation

In this work, laser direct energy deposition technology was used to produce hybrid manufactured TC17 titanium alloy with wrought substrate. The cyclic deformation behavior in the total strain range of 1.5%, 2.0%, 2.5%, and 3.0% at ambient temperature and dislocation morphology was investigated. The experimental results show that the three specimens represent cyclic softening when the total strain range is large than 1.5%. All the hybrid manufactured specimens are fractured in the deposition zone and the size of the deformated α phase decreases with increased strain. Slip transfer between α phase and β matrix and a small amount of dislocation tanglement in β matrix was observed in the specimen with strain of 1.5% and cyclic hardening. The dislocation density in β phase increased abruptly when the strain range is 2.5%, which promotes cyclic softening. The heterogeneous deformation between the high and low density dislocation zones formed in the α phase of the cyclic softening samples is the cause of the deformation and fracture of the α phase. The tension-compression asymmetry under forward and reverse loading revealed the Bauschinger effect in specimens with total strain exceeding 1.5%. Dislocation tanglement promoted cyclic softening by increasing the local back stress, at the same time, the back stress helped easier dislocation movement during reverse loading. Meanwhile, dislocation rearrangement and annihilation reduced the friction stress and further accelerate cyclic softening.

Effect of Initial Grain Size on Microstructure and Mechanical Properties of In Situ Hybrid Aluminium Nanocomposites Fabricated by Friction Stir Processing

Friction stir processing (FSP) offers a unique opportunity to tailor the microstructure and improve the mechanical properties due to the combination of extensive strains, high temperatures, and high-strain rates inherent to the process. Reactive friction stir processing was carried out in order to produce in situ Al/(Al13Fe4 + Al2O3) hybrid nanocomposites on wrought/as-annealed (673 K) AA1050 substrate. The active mixture of pre-ball milled Fe2O3 + Al powder was introduced into the stir zone by pre-placing it on the substrate. Microstructural characterisation showed that the Al13Fe4 and Al2O3 formed as the reaction products in a matrix of the dynamically restored aluminium matrix. The aluminium matrix means grain size was found to decrease markedly to 3.4 and 2 μm from ~55 μm and 40–50 μm after FSP using wrought and as-annealed substrates employing electron backscattered diffraction detectors, respectively. In addition, tensile testing results were indicative that the fabricated surface nanocomposite on the as-annealed substrate offered a greater ultimate tensile strength (~160 MPa) and hardness (73 HV) than those (146 MPa, and 60 HV) of the nanocomposite formed on the wrought substrate.

Additive manufacturing-based repair of IN718 superalloy and high-cycle fatigue assessment of the joint

Room-temperature high-cycle fatigue (HCF) of IN718 repaired joint via laser direct energy deposition (DED) were studied with the fatigue axis perpendicular to the joint interface. Solution treated and aged (STA) were compared with directly aged (DA) conditions. The wrought IN718 substrate showed equiaxed grains with a size of ~90 μm and a high fraction of annealing twins, whereas the DED deposit revealed a mixture of equiaxed and columnar grains with an average size of ~20 μm. There was little difference between the STA and DA conditions in the grain length-scale. Micro-hardness results highlighted the need for the heat treatment as it can remove the heat-affected zone and hardness dip, creating a uniform hardness profile across the joint. Although the monolithic DED deposit had a similar tensile strength to the wrought substrate, the DED joint exhibited an overall decreased HCF performance, regardless of the heat treatment conditions. When the fatigue stress was low, the STA condition had a better HCF performance than the DA, however, the opposite trend appeared for the high stress, resulting in a cross-over point on the stress-life S - N plot. Interrupted fatigue tests, combined with microscopy and fractography, revealed that the fatigue failure occurred in the substrate for the DED joint in the DA condition, whilst in the deposit zone for the STA condition due to the distribution and fracture of the Laves and δ phases. Grain boundary cracking in the substrate near the substrate-to-deposit interface can occur in both cases, probably due to the Nb-rich liquid films. • High-cycle fatigue of AM IN718 repaired joints with loading perpendicular to the interface • Post heat treatment can effectively eliminate the heat affected zone • Directly aged joint outperforms the solution treated and aged joint under high fatigue stress • Whereas the solution treated one performs better under low fatigue stress • Such an unexpected phenomenon is reconciled using single-specimen interrupted tests

Interface Joint Strength between SS316L Wrought Substrate and Powder Bed Fusion Built Parts.

Metal powder bed fusion (PBF) additive manufacturing (AM) builds metal parts layer by layer upon a substrate material. The strength of this interface between the substrate and the printed material is important to characterize, especially in applications where the substrate is retained and included in the finished part. Ensuring that this interface between the original and the printed material has adequate material properties enables the use of this PBF AM process to repair existing structures and create new parts using both AM and conventional manufacturing. This paper studies the tensile and torsional shear strengths of wrought and PBF-built SS316L specimens and compares them to specimens that are composed of half wrought material and half PBF material. These specimens were created by building new material via PBF onto existing wrought SS316L blocks, then cutting the specimens to include both materials. The specimens are also examined using optical microscopy and electron backscatter diffraction (EBSD). The PBF specimens consistently exhibited higher strength and lower ductility than the wrought specimens. The hybrid PBF/wrought specimens performed similarly to the wrought material. In none of the specimens did any failure appear to occur at or near the interface between the wrought substrate and the PBF material. In addition, most of the deformation in the PBF/wrought specimens appeared to be limited to the wrought portion of the specimens. These results are consistent with optical microscopy and EBSD showing smaller grain size in the PBF material, which correlates to increased strength in SS316L due to the Hall–Petch relationship. With the strength at the interface meeting or exceeding the strength of the original wrought material, this process shows great promise as a method for adding additional features or repairing existing structures using metal PBF AM.

Microstructure and mechanical properties of forging-additive hybrid manufactured Ti–6Al–4V alloys

The forging-additive hybrid manufacturing technology has combined the advantages of traditional manufacturing in efficiency and cost with those of additive manufacturing in flexibility and rapid prototyping, thus can provide an effective solution for the efficient forming of large and complex components. In this kind of manufacturing technology, the heat affected zone (HAZ, also called as bonding zone) between the wrought substrate zone (WSZ) and the laser deposition zone (LDZ) is the key to the properties of final components. In this study, the powder-feeding laser additive manufacturing technology was employed to deposit bulk samples on a wrought Ti–6Al–4V substrate containing bimodal microstructures. The microstructures and mechanical properties of hybrid manufactured Ti–6Al–4V alloys were studied with emphasis on the HAZ. The results show that, due to the different history of thermal, a graded microstructure was formed from the bottom to the top of HAZ. The bimodal microstructure at the bottom-HAZ gradually transformed to a mixed structure contained equiaxed α, lamellar α, and a large number of secondary α in the middle-HAZ, while the top-HAZ exhibits Widmanstätten structures consisting lamellar α and the so-called ghost structures due to the insufficient diffusion of alloying elements. The measurement of mechanical properties shows that, the sample with bonding zones presents higher tensile strength and yield strength, but lower elongation than those without bonding zones (WSZ or LDZ). The fracture positions of all samples with bonding zones are in WSZ and far away from HAZ, indicating a better strength of bonding zone than that of the wrought substrate and the laser deposition part due to the formation of secondary α and fine lamellar α in HAZ.

Compatibility research of laser additive repairing TA15 forgings with Ti6Al4V-xTA15 alloy

The application of mixed powders with different mass fraction on laser additive repairing (LAR) can be an effective way to guarantee the performance and functionality of repaired part in time. A convenient and feasible approach is presented to repair TA15 forgings by employing Ti6Al4V-xTA15 mixed powders in this paper. The performance compatibility of Ti6Al4V-xTA15 powders from the aspects of microhardness, tensile property, heat capacity, thermal expansion coefficient and corrosion resistance with the TA15 forgings was fully investigated. The primary α laths were refined and the volume fraction of the secondary α phase was increased by increasing the mass fraction of TA15 in the mixed Ti6Al4V-xTA15 powders, leading to varied performances. In conclusion, the mixed Ti6Al4V-70%TA15 (x=70%) powders is the most suitable candidate and is recommended as the raw material for LAR of TA15 forgings based on overall consideration of the compatibility calculations of the laser repaired zone with the wrought substrate zone.

The Interface Microstructures and Mechanical Properties of Laser Additive Repaired Inconel 625 Alloy.

The microstructure and micro-mechanics around the repaired interface, and the tensile properties of laser additive repaired (LARed) Inconel 625 alloy were investigated. The results showed that the microstructure around the repaired interface was divided into three zones: the substrate zone (SZ), the heat-affected zone (HAZ), and the repaired zone (RZ). The microstructure of the SZ had a typical equiaxed crystal structure, displaying simultaneously precipitated block-shaped MC-type carbides (NbC, TiC), with bimodal sizes of approximately 10 μm and 0.5 μm and an irregularly shaped flocculent Laves phase. Recrystallization occurred in the HAZ, and led to significant grain growth; a portion of the second phase dissolved in the original grain boundaries. In the RZ, there was a columnar crystal structure, and the size increased with increasing deposition thickness. Moreover, the microstructure between the layer interface and layer interior was quite different, presenting an overlapping transition zone (OTZ), in which the dendritic structure coarsened and more Laves phase were precipitated, compared to in the layer interior. The hardness and tensile properties of the LARed samples were equivalent to those of the wrought substrate, which indicates that laser additive repairing (LAR) is a reliable repair solution for damaged and mis-machined components comprising Inconel 625 alloy.

Machining of directed energy deposited Ti6Al4V using adaptive control

Additively manufactured (AM) components possess microstructures different from conventional forms in the same material and as a consequence, the mechanical properties and machinability of components produced using these technologies differ. Also, the microstructures from these processes are often anisotropic and as such different regions possess varying properties and hence varying response during post process machining. An adaptive control (AC) machining system for addressing this variation in microstructures during post process machining is developed here and its use demonstrated in this paper.The adaptive control system is used in milling and drilling trials for machining components manufactured by Directed Energy Deposition (DED). Surface roughness and residual stress analysis in the ‘as built’ state and after post process machining with the prevailing cutting forces are also presented here. Microstructures of the deposited material and the subsurface effects at the machined region due to the action of the cutting tool is also analysed.Milling trials are investigated from the standpoint of the use of adaptive machining for the removal of the outermost layer of DED produced Ti6Al4V and in the machining of bulk regions after preliminary machining of the undulating layer. Drilling experiments are carried out for investigating the effects of the machining process on the resulting surface condition, comparing the process with and without adaptive control. The effects of variation in cutting forces during drilling through the different material systems comprising of the DED region and the wrought substrate is also discussed. The effect of periodic changes in cutting forces during machining due to the variation in microstructure along the build direction is analysed and discussed. The use of adaptive control machining for post processing is shown to improve surface finish as it reduces the initiation and generation of chatter marks on the machined surface resulting from material anisotropicity.

Cracks Repairing by Using Laser Additive and Subtractive Hybrid Manufacturing Technology

Abstract A laser additive and subtractive hybrid manufacturing technology was proposed to repair Inconel 718 cracks in this paper. Microstructures and the mechanical properties such as the micro-hardness, the tensile strength, and the friction-wear of the repair zone were investigated in detail. The microstructure analysis showed that a metallurgical bonding could be achieved between the repair zone and the matrix. The typically columnar and dendrite crystal appeared in the repaired zone, and the crystal epitaxial grew along the deposition direction, and the heat-affected zone in the groove boundary was coarse equiaxial crystal. The mechanical test result showed that the micro-hardness and tensile strength of the repaired tissue was about 87% and 89% of the original Inconel 718 wrought substrate. And, the wear resistance of the repaired zone was similar to that of the substrate. It was found that the surface quality of the repair zone for laser polishing is better than that for mechanical milling.

Microstructure and Tribological Properties of Laser Forming Repaired 34CrNiMo6 Steel.

Laser forming repair (LFR) technology has considerable potential in high strength steel structure repair. 34CrNiMo6 steel has been widely used in high-value components, and it is imperative to repair these damaged components. In this study, two different thicknesses of repaired layers are deposited on the 34CrNiMo6 wrought substrate with five layers and 20 layers via LFR technology. The microstructure, phases, microhardness, and tribological properties are analyzed using optical microscopy, scanning electron microscopy, X-ray diffraction, Vickers hardness testing, and dry sliding wear testing. These results show that the 34CrNiMo6 repaired layers were successfully deposited on the substrate. The microstructure of the laser-repaired layers in the five-layer sample included bainite and retained austenite. For the 20-layer sample, the microstructure in the top of the repaired layers was still bainite and retained austenite, whereas that in the bottom of the repaired layers was transformed into ferrite and cementite. The average coefficients of friction of repaired layers is not significantly different from the substrate. The wear rate of the five LFR layers, 20-layer LFR, and substrate samples were 12.89 × 10−6, 15 × 10−6, and 23.87 × 10−6 mm3/N·m, respectively. The laser forming repaired samples had better wear resistance compared to the substrate. The wear mechanism of laser forming repaired samples is abrasive wear; whereas that of the substrate is abrasive wear and fatigue wear.

Characterization and mechanical properties of cladded stainless steel 316L with nuclear applications fabricated using electron beam melting

The ability to fabricate or join components of 316 L austenitic stainless steel using additive manufacturing (AM) processes such as laser and electron beam melting (EBM®) offers several advantages including enhanced part complexity, narrow or absent heat affected zones, increased part precision, avoidance of filler materials (such as traditional welds), and the ability to create metallurgically sound bonds. These attributes can contribute to improved mechanical properties of the fabricated components and component repair in nuclear, aerospace, and chemical industries. In the present work, we report that austenitic 316 L stainless steel additively manufactured by EBM exhibits a 76% increase in the yield strength and a corresponding increase of 29% in the ultimate tensile strength in contrast to the wrought substrate and commercial forged 316 L stainless steel. The EBM clad 316 L stainless steel elongation was 36%. The wrought substrate equiaxed grain size was ∼30 μm in contrast to elongated, columnar grains ∼0.1 mm wide and >1 mm in length for the EBM cladding. Transmission Electron Microscopy (TEM) analysis revealed that these columnar grains, which exhibited very straight, and presumably special grain boundaries having a very high (100) texture, contained a variety of sub-grain microstructures consisting of low-angle sub-grain boundaries containing dislocation tangles and stacking-fault arrays, and homogeneously distributed Cr23C6 carbide precipitates, with no preferential carbide precipitation on either the straight, special columnar grain boundaries, or the very low-angle sub-grain boundaries. This observation and the formation of hierarchical microstructures which produce high strength and possibly corrosion resistance as a consequence of the absence of grain boundary carbide precipitation, illustrate the prospects for AM as a novel concept for achieving grain boundary engineering to promote high-strength and corrosion resistant alloys for high-temperature, corrosive environments, including elevated temperature nuclear reactor applications.

Microstructure and mechanical properties of laser additive repaired Ti17 titanium alloy

Abstract Laser additive manufacturing technology with powder feeding was employed to repair wrought Ti17 titanium alloy with small surface defects. The microstructure, micro-hardness and room temperature tensile properties of laser additive repaired (LARed) specimen were investigated. The results show that, cellular substructures are observed in the laser deposited zone (LDZ), rather than the typical α laths morphology due to lack of enough subsequent thermal cycles. The cellular substructures lead to lower micro-hardness in the LDZ compared with the wrought substrate zone which consists of duplex microstructure. The tensile test results indicate that the tensile deformation process of the LARed specimen exhibits a characteristic of dramatic plastic strain heterogeneity and fracture in the laser repaired zone with a mixed dimple and cleavage mode. The tensile strength of the LARed specimen is slightly higher than that of the wrought specimen and the elongation of 11.7% is lower.

Tensile Fracture Behavior and Failure Mechanism of Additively-Manufactured AISI 4140 Low Alloy Steel by Laser Engineered Net Shaping.

AISI 4140 powder was directly deposited on AISI 4140 wrought substrate using laser engineered net shaping (LENS) to investigate the compatibility of a LENS-deposited part with the substrate. Tensile testing at room temperature was performed to evaluate the interface bond performance and fracture behavior of the test specimens. All the samples failed within the as-deposited zone, indicating that the interfacial bond is stronger than the interlayer bond inside the deposit. The fracture surfaces were analyzed using scanning electron microscopy (SEM) and energy disperse X-ray spectrometry (EDS). Results show that the tensile fracture failure of the as-deposited part is primarily affected by lack-of-fusion defects, carbide precipitation, and oxide particles inclusions, which causes premature failure of the deposit by deteriorating the mechanical properties and structural integrity.