Direct Metal Deposition Research Articles

A comparative study on corrosion and mechanical properties of laser-cladded X2CrNiMoN22-5-3 duplex stainless steel on 42CrMo4 steel substrate

Duplex stainless steel is an alloy that combines the advantages of austenitic stainless steel and ferritic stainless steel. It has excellent corrosion resistance, high strength, and good weldability. One of the main problems in marine shafts using X2CrNiMoN22-5-3 Duplex Stainless Steel (2205) is bending and warping over time. In this study, 42CrMO4 (MO40) steel was clad with 2205 dual-phase steel using direct metal deposition with wire to simultaneously utilize the mechanical properties, and corrosion resistance. Perform metallographic imaging, corrosion test, and tensile test, to maintain the quality of the cladding. The results show that the corrosion potential of 2205 cladding layer is −0.65 (including semi-passive zone), while the control sample of 2205 had a corrosion potential of −0.26, and the MO40 substrate had a corrosion potential of −0.1 (highlighting the advantage of the cladding in thermodynamics term). EIS results showed that the REISMO40=2325Ω, REIS2205=24315Ω, and REIS2205cladded=216133Ω. The corrosion rate for the substrate, control sample, and laser-clad sample were 0.33, 0.15, and 0.00095 mm/year, respectively, without significant loss in tensile properties. The final strength for MO40(with 2205 clad) reaches 672 MPa with a 14 % decrease from 788 for MO40. In this case, we still have a 36 % increase in strength compared to the 2205 sample. It seems that the bent problem of the pure 2205 marine shaft can be solved completely in this case and continues to be solved in our ongoing work.

Evaluation of hydrogen embrittlement susceptibility of underwater laser direct metal deposited 316L stainless steel

Underwater laser direct metal deposition (UDMD) shows great application potential in underwater high-performance repair. The susceptibility of underwater repaired components to hydrogen embrittlement (HE) is not extensively researched yet. In this study, HE in 316L stainless steel repaired by UDMD is systematically investigated and compared with in-air direct metal deposited (DMD) 316L and conventionally manufactured (CM) 316L. The experimental results show that the high cooling rates involved in UDMD contribute to a “austenite-ferrite” solidification mode. The cellular structure with a high-density of dislocations increases the tensile strength of as-built UDMD 316L. Thermal desorption spectroscopy analysis reveals that the hydrogen concentrations are similar for 316L manufactured by three processing methods, suggesting that the complex microstructural features by UDMD and DMD do not provide additional H-trapping sites. SSRT results show that the HE susceptibility is in the sequence: CM 316L (30.7%) > UDMD 316L (15.1%) > DMD 316L (9.6%). Compared with CM 316L, the stable cellular structure and higher stability towards martensitic transformation of as-built 316L are beneficial for the HE resistance. In the hydrogen-charged UDMD 316L, the hydrogen-assisted dislocation movement and mechanical twinning formation enhance the localized plasticity and induce cracking. The micron-sized oxide particles and micro-pores further contribute to the fast decohesion of interfaces in the presence of hydrogen. Those combined effects lead to the reductions in tensile strength and elongation of the hydrogen-charged UDMD 316L.

Combination effects of laser heating and water cooling on the repair performance of Hastelloy C-276 by underwater laser direct metal deposition

The Ni-based Hastelloy C-276 was repaired by in-air and underwater laser direct metal deposition (in-air DMD and UDMD) with four gradient cooling rates (in-air DMD, in-air DMD with interlayer cooling, UDMD and UDMD with each layer re-covered by water). The microstructure and mechanical properties of repaired samples were systematically characterized with respect to the cooling rates. All samples presented good metallurgical bonding and columnar dendrites with epitaxial growth. The underwater environment had a more pronounced acceleration effect on the cooling rate compared to interlayer cooling. The rapid cooling induced intense thermal cycling, resulting in increased dislocation density and grain refinement with primary dendrite arm spacing (PDAS) diminishing from 5.30 to 3.21 μm. Accelerated cooling rate contributed to precipitation of massive M6C carbides. Carbides coarsened (sizes from 257 to 354 nm) and exhibited a reduced content as cooling rate slowed down due to intrinsic heat treatment (IHT). The residual water film in UDMD repair promoted oxide formation. Samples with increased cooling rates exhibited superior mechanical performance. The improved microhardness, tensile and impact properties were primarily attributed to the enhanced fine grain strengthening and Orowan strengthening facilitated via reduced grain size, increased dislocation density and carbide content. Quantities of large-size carbides were detrimental to tensile and impact properties as displayed in the in-air DMD sample with interlayer cooling (carbide size of 341 μm). The study could serve as a reference for in-situ restoration in deep-water environments.

Influence of Surface Chemistry on Metal Deposition Outcomes in Copper Selenide-Based Nanoheterostructure Synthesis.

The use of nanoparticle surface chemistry to direct metal deposition has been well-studied in the modification of metal nanoparticle substrates but is not yet well-established for metal chalcogenide particle substrates, although integration of these particles into nanoheterostructures is of high interest. In this report, we investigate the effect of Cu2-xSe surface chemistry on the morphology of metal deposition on these plasmonic semiconductor nanoparticles. Specifically, we functionalize Cu2-xSe nanoparticles with a suite of 12 different ligands and investigate how different aspects of the ligand structure do or do not impact the morphology and extent of subsequent metal deposition on the Cu2-xSe surface. Surprisingly, our results indicate that the morphology of the resulting metal deposits and the extent of metal deposition onto the existing Cu2-xSe particle substrate are indistinguishable for the majority of ligands tested. An exception to these findings is observed for particles functionalized by quaternary alkylammonium bromides, which exhibit statistically distinct metal deposition patterns compared to all other ligands tested. We hypothesize that this unique behavior is due to a cooperative binding mechanism of the quaternary alkylammonium bromides to the surface of copper selenide. Taken together, these results yield both new strategies for controlling postsynthetic modification of copper selenide nanoparticles and also reveal limitations of surface chemistry-based approaches for this system.

Integrating data-driven system to predict temperature and distortion in multi-layer direct metal deposition processes

This study proposed a framework to train an artificial neural network (ANN) by a data-driven system to predict the temperature and distortion in multi-layer direct metal deposition (DMD) of SS 304. By integrating thermomechanical variables, the research ensures the fidelity of finite element (FE) simulations, which are validated against existing data. Notably, the study achieves enhanced precision over prior work by varying the heat input sources and heat transfer equations. A novel aspect of this research is the use verified FE simulation to add data to data-driven system to train an efficient ANN for predicting temperature and distortion based on key parameters such as laser power and scanning speed. The iterative process involved multiple FE simulations with varying laser parameters to refine the ANN’s predictive capabilities. This methodology enabled the identification of relationships between manufacturing parameters, temperature, and distortion. The iterative training continued until the ANN’s predictions and subsequent FE simulation results converged within an acceptable margin. The findings confirm that the trained ANN can predict temperature and distortion both accurately and expediently, marking a significant advancement in the control of the DMD process.Graphical

Quantifying the effects of inlet gas and collision models in direct metal deposition using a CFD-DEM approach

Simulations of the powder jet in direct metal deposition (DMD) are often made with significant simplifications such as being incompressible, steady-state, or single-component, and do not provide explanation for the choice of parameters in the collision model. This work presents a coupled Computational Fluid Dynamics–Discrete Element Method model for the powder jet in DMD that considers all of the following features: compressibility effects, particle–wall and particle–particle collisions, turbulence, gas mixing, and melt pool boundaries. The goal of the simulation is to optimize the operating conditions and to predict the outcomes of experiments. After effective validation against experimental results, the effects of inlet gas, collision models and different boundary conditions in DMD have been comprehensively studied. It is demonstrated that gases with higher diffusivities, such as helium, are less effective shielding gases than those with lower diffusivities, such as argon. The increased wall temperature arising from the melt pool and track has little influence on the particle distribution.

Effect of the Cooling Liquid on the Milled Interface in the Combined Process of Milling and Direct Metal Deposition.

The combination of Direct Metal Deposition (DMD) with milling offers numerous advantages for the manufacturing of complex geometry parts demanding high dimensional accuracy and surface quality. To reach this, a process strategy alternation between both processes is often required, leaving the milled surface with a layer of cooling fluid before adding material by DMD. This paper investigates the effect of cooling liquid on the milled interface in the combined process of milling and DMD. Five different interface conditions were examined, employing four distinct cleaning techniques to assess their impact on the quality of the interface. Key metrics analysed included hydrogen content, carbon content, and porosity levels at the interface. Cleaning techniques were evaluated to determine their necessity in enhancing the interface quality in the combined DMD and milling production process. Results from this study provide essential insights into the optimal cleaning requirements for improving the interface integrity in hybrid manufacturing processes, which could lead to more reliable and efficient production methods in industrial applications.

Влияние технологических параметров процесса прямого лазерного выращивания на качество формируемого объекта из титанового сплава ВТ23

Introduction. Laser engineered net shaping (LENS) or Direct metal deposition (DMD) is considered as a promising method for manufacturing products of complex configurations from titanium-based alloys, as it allows minimizing the use of machining and loss of material to waste. Currently, neither the LENS technological process of titanium alloy VT23 has not been developed, nor the structural features of the alloy after LENS have not been studied, which will make it possible to determine the scope of application of the material after LENS. The purpose of this study is to determine optimal modes of the LENS process for manufacturing of quality parts from titanium alloy VT23. Methodology. The alloy specimens obtained with laser power 700÷1300 W in increments of 100 W and scanning speed 600÷1,000 mm/min in increments of 200 mm/min and distance between adjacent laser tracks 0.5–0.9L (L — track width) in increments of 0.2L were analyzed in the study. The elemental composition of the powder material was studied by X-ray fluorescence analysis and reducing combustion in a gas analyzer, the structure of the objects obtained by LENS was analyzed by metallographic and X-ray phase analysis methods as well as microhardness was determined. Results and discussion. It is established that high-quality objects without cracks, with low porosity can be synthesized from VT23 alloy by LENS method using the following modes: laser power 700÷1100 W, scanning speed 800–1,000 mm/min, track spacing 0.5–0.7 of the individual track width L. It is shown that after all investigated LENS modes, the VT23 alloy had a dispersed (α+β) structure of the “basket weave” type. It is revealed that regardless of LENS mode the amount of β-phase in the alloy structure is about 30 %. It is shown that the microhardness of the deposited material does not depend on LENS modes and is 460 HV.

Reducing Oxidation during Direct Metal Deposition Process: Effects on Ti6Al4V Microstructure and Mechanical Properties

The production of materials with a high affinity for oxidation using the direct metal deposition (DMD) process requires an extended process examination that goes beyond the usual, purely energetic consideration, with the aim of providing sufficient energy to melt the substrate and the powder material supplied. This is because the DMD process does not allow any conclusions to be drawn as to whether it and its respective selected parameters result in an oxidation critical process. To assess this, a superposition of the temperature field with the existing spatial oxygen concentration is required. This work uses this approach to develop an oxidation model that reduces oxidation during the DMD process. In addition to the numerical model, an analytical model is derived, with which the temperature of a material element can be calculated analytically and the resulting boundary oxygen concentration calculated using Fick’s 2nd law. The model also takes into account two-stage oxidation kinetics for Ti alloys. The effect of too high a travel speed (with the same specific energy of the other experiments) is shown visually in the numerical calculation of the temperature field. However, if the process model is taken into account, the components do fulfil the specified requirements. Finally, the effect of oxidation on the microstructure, microhardness, ultimate strength, yield strength and elongation at failure of Ti6Al4V structures produced using DMD is also investigated, and further supports our conclusions regarding the effectiveness of the proposed model.

Comprehensive Distortion Analysis of a Laser Direct Metal Deposition (DMD)-Manufactured Large Prototype Made of Soft Martensitic Steel 1.4313

Additive manufacturing (AM) by using direct metal deposition (DMD) often causes erratic distortion patterns, especially on large parts. This study presents a systematic distortion analysis by employing numerical approaches using transient–thermal and structural simulations, experimental approaches using tomography, X-ray diffraction (XRD), and an analytical approach calculating the buckling distortion of a piston. The most essential geometrical features are thin walls situated between massive rings. An eigenvalue buckling analysis, a DMD process, and heat treatment simulation are presented. The eigenvalue buckling simulation shows that it is highly dependent on the mesh size. The computational effort of the DMD and heat treatment simulation was reduced through simplifications. Moreover, artificial imperfections were imposed in the heat treatment simulation, which moved the part into the buckling state inspired by the experiment. Although the numerical results of both simulations are successful, the eigenvalue and DMD simulation cannot be validated through tomography and XRD. This is because tomography is unable to measure small elastic strain fields, the simulated residual stresses were overestimated, and the part removal disturbed the residual stress equilibrium. Nevertheless, the heat treatment simulation can predict the distortion pattern caused by an inhomogeneous temperature field during ambient cooling in an oven. The massive piston skirt cools down and shrinks faster than the massive core. The reduced yield strength at elevated temperatures and critical buckling load leads to plastic deformation of the thin walls.

Effects of TiC addition on the interface stability, microstructure, and mechanical properties of IN718 fabricated by laser direct metal deposition: A combined experimental, DFT and MD study

In this study, we reveal the impact of the addition of TiC in the IN718 superalloys at both atomic and micron scales through density functional theory (DFT), molecular dynamics (MD), and experimental analysis. From the micro scales, the addition of TiC can effectively mitigate the segregation behavior of Nb and Mo atoms, promote heterogeneous nucleation, reduce grain size, and thus improve mechanical properties. From the atomic scales, the effect of alloying elements (Fe, Cr, Mo, Nb, Co) on the stability of the TiC/γ-Ni interface was investigated through first principles. Co-doping interface was more stable than other interfaces by MD calculations, followed by Cr and Fe-doping models. The heat of segregation results inferred that TiC can effectively mitigate the segregation behavior of Nb and Mo atoms in the TiC/γ-Ni interface, it is mutually verified with the experimental results. Furthermore, the interface energy values theoretically illustrated that TiC particles could promote the heterogeneous nucleation of γ-Ni, this behavior of TiC particles was verified by experiment results. This investigation results provide reference information in the study of ceramic particle reinforced alloys at atomic and micron scales.

Experimental study of SS316L, Inconel 625, and SS316L-IN625 functionally graded material produced by direct laser metal deposition process

Three types of walls were produced by the direct laser metal deposition (DLMD) process; SS316L, Inconel 625 (IN625), and SS316L-Inconel 625 FGM. The thin walls were deposited on an AISI 4130 austenitic steel substrate in five layers with a length of 2 cm. The solidification behavior, secondary dendrite arm spacing (SADS) value, chemical composition, and hardness of samples were studied. Microstructures were evaluated using optical microscopy (OM) images, scanning electron microscopy (SEM), EDS Line, EDAX, and Map analyses. OM and SEM images showed an acceptable bonding between the layers in all samples. The main solidification was equiaxed dendritic and columnar dendritic in most parts. The growth of dendrites was perpendicular to the substrate. Some dendrites grew epitaxially at the interface of two sequential layers. The standard deviation of SDAS value for SS316L, IN625, and SS316L-IN625 FGM was 0.63, 0.71, and 0.73, respectively. The lowest value of SDAS was obtained in layer one, while the highest value was obtained in layer five of the thin walls. The average SDAS values for SS316L, IN625, and SS316L-IN625 FGM were 4.40, 4.53, and 4.76 µm, respectively. Therefore, the difference between the SDAS values was not significant. EDAX and Map analyses showed that the segregation of Nb and Mo to the dendritic boundary and the formation of eutectic, secondary phases, and brittle Laves phases have occurred. Additionally, the segregation of Nb and Mo to the dendritic boundary in the SS316L-IN625 FGM sample was higher than SS316L and IN625 samples. The microhardness values oscillated significantly and decreased by moving away from the substrate (in the build direction). The microhardness values of different points of the SS316L-IN625 FGM walls were in the range of 218–278 HV. EDS line scan, microstructure, and microhardness analyses indicated the successful fabrication of the SS316L-IN625 FGM by the DLMD process.

Tailoring of the Microstructure and Mechanical Properties of High Nitrogen Steel Repaired by Underwater Laser Direct Metal Deposition

Tailoring of the Microstructure and Mechanical Properties of High Nitrogen Steel Repaired by Underwater Laser Direct Metal Deposition

A review of energy efficiency and Machine learning analysis for additive manufacturing of direct laser metal deposition

Additive Manufacturing (AM) is an innovative industrial process that utilizes layering of materials to create unique products with an unprecedented level of flexibility. To maximize the benefits of AM, it is crucial to understand the precise utilization of laser energy. This review provides a concise overview of the Directed Laser Metal Deposition (DLMD) process, which includes an analysis of input parameters and the effective use of laser power, along with the impact of laser synchronous preheating processes. Various input parameters such as travel speed, hatch spacing, powder feed rate, and the standard of distance influence the calculation of volumetric energy density (VED). VED is important for Clad bed geometry, including dilution (D), height (H), width (W) of AM wall, and clad bead stability (ΔH). In the field of manufacturing, Machine Learning (ML) is a commonly used subset of Artificial Intelligence (AI) to improve the quality of processes, expedite production, and reduce costs. Specifically, in Metal Additive Manufacturing (MAM), ML techniques are leveraged to optimize various process parameters, resulting in the production of high-quality, defect-free products. This review provides a detailed explanation of the step-by-step implementation process of ML and its classification within a fundamental structure.

Research on gas pore formation and inhibition mechanism of high nitrogen steel during laser direct metal deposition

Nitrogen pore formation is an inherently tricky problem that limits the application of high nitrogen steel (HNS) in various fields. In the present study, a CA-LBM coupling model was proposed to understand the nitrogen pore formation mechanism during laser direct metal deposition (DMD) of HNS. Based on the proposed model and theoretical analysis, the effects of pulse frequency and shielding gas nitrogen content on the porosity were clarified systematically. Results showed that after the onset of solidification, the ferrite phase with extremely low nitrogen solubility precipitated first, inducing the continuous enrichment of nitrogen in the residual liquid phase, which in turn provided the prerequisite for nitrogen pore nucleation. The application of quasi-continuous-wave (QCW) laser mode accelerated the molten pool solidification, and shortened the nitrogen supersaturated region, allowing more nitrogen to be solid dissolved in the matrix. On this basis, the porosity was inhibited to a certain extent. Compared with the high-frequency pulse, the low-frequency pulse showed better porosity inhibition. In addition, following the classic nucleation theory, nitrogen segregation and nitrogen solubility synergistically dominated nitrogen pore formation. The nitrogen partial pressure, determined by the shielding gas nitrogen content, played a dual role in porosity defects. Elevated nitrogen partial pressure served to increase nitrogen solubility while promoting the nitrogen absorption process to intensify nitrogen segregation. However, due to the short duration of the molten pool, the nitrogen absorption process could not be fully processed. Nitrogen solubility enhancement was the key factor in inhibiting porosity during the DMD process.

The dynamic carbon footprint modeling for laser direct metal deposition based on processing states

The Laser Direct Metal Deposition (LDMD) process offers notable advantages and obtains wide application in aerospace, defence equipment and other industrial sectors. However, the characteristics of multiple-inputs and low-efficiency in the process will bring about high carbon footprint. Additionally, the carbon footprint fluctuates with processing states and equipment systems owing to the discontinuous process in LDMD involving the layer-by-layer deposition and the laser-powder coupling. This paper investigated dynamic carbon footprint based on the resource and energy consumption from the process-oriented standpoint in LDMD process, which quantified the processing time, power distribution and material consumption of each processing state for every sub-system. In this research, the discontinuous process was divided into effective processing state, rapid moving state and transformed delay state and the processing time of each state were estimated with process parameters. Besides, the operating state time and power distribution of five sub-systems were estimated combining the equipment triggering mechanism and the processing state time. The orthogonal experiment was carried out to deposit the 316L stainless steel powder into parts with the size of 15 mm*15 mm*10 mm under the given process parameter conditions (Vf ∈ [8,12] g/min, P ∈ [600,1000] w, Vs ∈ [500,900] mm/min). The results show that carbon footprint of deposited parts fluctuates in the range of 3624.68–15759.08 g under parameter combinations and the low carbon footprint parameter-interval is obtained. The average carbon footprint of effective processing state, the transformed delay state and the rapid moving state account for 55%, 40% and 5% respectively, while the carbon footprint of powder supply sub-system contributes to 68% among the five sub-systems. This research revealed and qualified the dynamicity of carbon footprint at the levels of processing states, process parameters and sub-systems, offering potential for carbon footprint reduction in advanced manufacturing processes.

Residual stress computation in direct metal deposition using integrated artificial neural networks and finite element analysis

Direct Metal Deposition (DMD) as a part of additive manufacturing processes, utilizes a laser heat source to deposit metallic material to construct components layer by layer, allowing for controlled manufacturing. DMD processes inherently induce residual stresses and distortions in the build part. While finite element (FE) analysis is one of the approaches to predict the residual stress, the high computational time required for the FE analysis makes it undesirable for the early stages of product development. This study extends a previously developed approach to more complex structures to evaluate the accuracy and computational efficiency of predicting residual stresses. For the present study, six different metallic structures with various complex shapes made from AISI 304 L were considered. Comparing the residual stress fields predicted by the integrated ANN-FE with thermomechanical FE analysis, the results demonstrated consistent distributions for all stress components across structures. Although localized regions exhibited higher errors, these areas coincided with low-stress zones, posing no critical concerns. Despite higher errors in some areas, most structures displayed prediction errors below 15%. Moreover, the analysis achieved a substantial computational efficiency enhancement of approximately 6 times for all structures analyzed.

Electrochemical passivation behavior and surface chemistry of 316 L stainless steel coatings on NV E690 steel fabricated by underwater laser direct metal deposition

The underwater direct metal deposition (UDMD) was employed to deposit 316 L stainless steel (SS316L) coatings on NV E690 steel. The chemical composition gradient from monolayer to trilayer SS316L induces an in-situ phase transformation, thereby enhancing the corrosion resistance. The steady-state passive film grew linearly with the applied potential and exhibited a bilayer structure: a high resistivity barrier layer and a low resistivity outer layer. The growth kinetics of the UDMD fabricated SS316L coatings align with the point defect model. Passive film is enriched in Cr while depleted in Fe and Ni, whereas the altered zone is enriched in Ni.

Oxygen Uptake of Ti6Al4V during Direct Metal Deposition Process

The efficient fabrication of titanium components using laser direct metal deposition (DMD) is gaining significant importance in the aerospace and medical sectors. The DMD process must be appropriately designed to address the issue of oxidation, as titanium exhibits a high affinity for oxygen. The carrier gas flow and shield gas flow, which have been considered secondary factors so far, are shown to exert a substantial influence on the gas dynamics of the DMD process. By varying these parameters, it is possible to identify the influence of the gas volume flows on the oxidation behavior exhibited during the DMD process. To quantify the oxygen uptake in titanium structures during buildup, hot carrier gas extraction is employed. Experiments are conducted using both a three-jet and a coaxial nozzle to assess the influence of nozzle geometry. Additionally, the experiments are conducted within a shielding gas chamber to demonstrate the benefits of such a chamber in mitigating oxidation. Finally, the study reveals that by appropriately combining the parameters of carrier gas volume flow, shield gas volume, and travel speed, it is possible to fabricate titanium components, which fulfill the requirements regarding oxygen content of aerospace and medical applications even without the utilization of a shielding gas chamber.

Effect of different feedstocks on the microstructure and mechanical properties of HSLA steel repaired by underwater laser direct metal deposition

Underwater laser direct metal deposition (UDMD) technique shows great potential for the on-site repair of damaged structures in the ocean. In this study, aiming at the possibility of flexible feedstock substitution, two powders with different properties are employed to repair the preprepared HSLA steel plates using UDMD. The combined effects of alloy compositions and UDMD processing on the repair performance including microstructure, mechanical properties and corrosion behavior, are systematically studied. The results show that the localized laser melting/solidification and rapid underwater cooling effect significantly increase the cooling rates, and thus lead to the formation of fine-grained lath martensite and acicular ferrite. The high Ni content in the sample repaired with ultra-high strength (UHS) powder contributes to the interlath austenite. Compared with that of the sample repaired with high strength (HS) powder, the microhardness of the sample repaired with UHS powder is high due to the solid solution strengthening and grain boundary strengthening. In addition, the tensile properties of the UDMD samples exceed the marine steel requirement (yield strength ≥690 MPa). The acceptable impact toughness of the UDMD samples is due to the existence of acicular structures and high fraction HAGBs. Furthermore, the UDMD samples present a better corrosion resistance in comparison with the substrate. The experimental findings demonstrate the employment feasibility of powder substitution on the UDMD repair of complex steel structures in the ocean.