Direct Laser Deposition Research Articles

On the Influence of Microstructure and Properties of Direct Laser Deposited 50Cr6Ni2Y Coatings with Different TiC Contents

Three 50Cr6Ni2Y + x wt.% TiC (x = 1.5, 3.0, 4.5) alloy steel coatings were prepared using direct laser deposition (DLD) technology. The microstructure, microhardness, and wear resistance of DLD samples were studied. The results indicate that DLD coatings were composed of α-Fe (Fe-Cr-Ti), γ-Fe (Fe-Ni), and TiC. When the added TiC content was 3.0 wt.%, the DLD coating without cracks was fabricated, and TiC particles were well embedded in the sample. In addition, the coating demonstrated the best performance, with a microhardness of 758 ± 23.3 HV0.2, an average friction coefficient of 0.58, and a wear rate of 0.37 %. The addition of an appropriate amount of TiC as a reinforcing phase, on the one hand, had played a role in the second phase strengthening. On the other hand, the diffusion interfaces formed between TiC particles and the matrix allowed some Ti elements to melt into the matrix and formed a solid solution, playing a role in solid solution strengthening. The results could provide a reference for the preparation and repair of laser additive manufacturing high-performance wear-resistant parts.

Effect of ultrasonic vibrations on mass efficiency and microstructure of laser direct deposition Inconel 718 superalloy

Laser direct deposition (LDD) is widely used to repair and manufacture high-value industrial components. However, it faces various defects, such as porosity, cracks, non-uniform microstructure, lack of fusion, keyhole phenomenon, element segregation, and undesirable secondary phases. A method to manage these defects is to concurrently apply ultrasonic vibrations (USV) during the LDD process. This study investigates the effect of USV on the mass efficiency and microstructure of LDD Inconel 718 superalloy to understand how incorporating USV can change the performance and structural integrity of single passes produced using the LDD process. For this purpose, USV is applied to a substrate during the LDD process. The resulting samples are characterized and analyzed using optical microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results indicate that applying USV below a threshold power value increases mass deposition by over 25%, while exceeding this threshold reduces it. Attention to this threshold power value is crucial for determining the process parameters, including laser power and speed. Additionally, USV transforms the microstructure from columnar to equiaxed and increases subgrain formation. This implementation also enhances the cooling rate, significantly decreasing the Laves phase by over 30% in all process parameters.

Correction: Investigation of Ti2AlNb Added TiAl Composite Prepared by Direct Laser Deposition

Correction: Investigation of Ti2AlNb Added TiAl Composite Prepared by Direct Laser Deposition

Alumina ceramic insulation layer for strain sensor fabricated by direct laser deposition

ABSTRACT Strain sensors are often used to monitor the use of critical components. The bond strength between the strain sensor and the gear teeth is particularly critical. There is a problem of insufficient bond strength between separated strain sensors and parts. The strain sensor is prone to loosening and flaking in the working environment. Therefore, a method of preparing the ceramic insulation layer of the strain sensor by direct laser deposition (DLD) is proposed. The effects of laser scanning trajectories, laser power, and scanning speed on forming quality were investigated experimentally. In addition, the phase analysis, microstructure characterization, and insulation properties of the insulating layers prepared at different overlap rates were researched. The research shows that the ceramic insulation layer has good insulation properties and hardness. The maximum hardness can reach 2405.74MPa, and the insulation resistance increases with the number of layers. The surface of the ceramic insulation layer is dense and has no cracks.

Synthesis of (Ti, Cr)xCy Carbides in VT6 Alloy by Direct Laser Deposition

Synthesis of (Ti, Cr)xCy Carbides in VT6 Alloy by Direct Laser Deposition

Microstructures and mechanical behaviors of a directional lamellar Ti-48Al-2Cr-2Nb alloy produced by laser additive manufacturing

Extremely large thermal gradient is considered as a unique characteristic of additive manufacturing, which can be utilized to fabricate directionally solidified alloys. In this study, we successfully fabricated a bulk Ti-48Al-2Cr-2Nb alloy with directional solidified features by the approach of direct laser deposition. The microstructural characterizations revealed that our additively manufactured (AMed) alloy was dominantly featured by a directional α2/γ lamellar microstructure. Moreover, there occurs an intriguing phenomenon that the orientation relationship between α2 and γ lamellae appears a slight deviation from the well-known Blackburn relationship, which was seldom observed in previous reports. Additionally, some amounts of βo and C14-type laves phases also formed and dispersed in the lamellar microstructure. Mechanical investigations indicate that the AMed alloy achieved an improvement in yield strength at room temperature. Moreover, its yield strength can remain 630 MPa at 800 °C, comparable to the value at room temperature, and only a slight decrease occurred when the temperature was increased to 900 °C, which is superior to that of the cast one. Then, the related strengthening mechanisms were discussed based on the directional lamellar features and the particularity in orientation relationship.

Direct Laser‐Deposited Ni36.5Co36.5Cr18Al4.5Ti4.5 Multiprincipal Component Alloy

Multiprincipal component alloys (MPCAs) have been extensively investigated and shown promising properties. The MPCAs also provide a new class of metallic alloys for additive manufacturing. Herein, a precipitation‐strengthened Ni36.5Co36.5Cr18Al4.5Ti4.5 MPCA is fabricated by direct laser deposition (DLD). The overall formability of the bulk is very good, only a few cracks exist near the bottom of the substrate. The as‐deposited samples feature a unidirectional epitaxial columnar grain microstructure with a high volume fraction (about 44%) of dispersed nanoscale γ′ phases and demonstrate a <100>//build direction texture. The as‐deposited samples exhibit a high yield strength about 896 MPa, an ultimate tensile strength about 1173 MPa, and an elongation about 17% along the build direction. These results demonstrate the feasibility of DLD for producing high‐volume fraction precipitation‐strengthened MPCAs without defects.

Investigation of Ti2AlNb-Added TiAl Composite Prepared by Direct Laser Deposition

Investigation of Ti2AlNb-Added TiAl Composite Prepared by Direct Laser Deposition

Analysis of thermal behavior and mass transport for manufacturing deep-small hole by ultra-high frequency induction-assisted laser wire deposition

Synchronous ultra-high frequency (UHF) induction-assisted laser deposition is an effective approach to tackle the extreme heat input and common defects that originate from laser direct deposition. The added auxiliary induction heat source can reduce the energy input of the laser heat source which guarantees the geometric integrity of the embedded tube and decreases temperature gradient. Meanwhile, the effective preheating of the induction heat source assures the metallurgical bonding among the substrate, deposited track and embedded tube. Experiments showed that the effective bonding can be formed among substrate-deposited track and deposited track-embedded tube under suitable combination parameters of the laser heat and induction heat. To gain insight into the hybrid deposition, a 3D numerical model coupled with multi-physical fields was established to explore the thermal process and flow behavior with assistance of induction heat. Results indicated that the electromagnetic force produced by induction coil promotes the flow velocity, which increases heat convection. Investigation on the induction heat parameter demonstrated that raising current intensity can accelerate the flow velocity from 0.07 m s-1 to 0.09 m s-1 while the maximum temperature of the molten pool declined from 2610 K to 2440 K owing to the reinforced heat convection. The experimental cross-section of the deposited tracks and the detected element distribution in transition areas are well tested against the numerical simulation results. The grain size in the top region of the deposited track is refined with increasing current intensity, which is experimentally and numerically verified by observed microstructure and G*R value. Meanwhile, the fabricated deposited track with average friction coefficient of 0.445 can be obtained when the laser and induction parameters are 1000 W and 400A, respectively.

Effect of scanning speeds on microstructure evolution and properties of 70Cr8Ni2Y coatings by direct laser deposition

Abstract The 70Cr8Ni2Y coatings were prepared by direct laser deposition (DLD) with different scanning speeds. The microstructure evolution and the relationship between microstructure and properties of the coatings were studied. The results demonstrated that the microstructure of DLD 70Cr8Ni2Y coatings was martensite, and the phases were α′ (Fe-Cr) and γ-Fe (Fe-Ni). With the increased of scanning speed, the martensite size decreased from 5.42 ± 0.04 μm to 4.42 ± 0.01 μm and 3.20 ± 0.02 μm. When the scanning speed was 20 mm s−1, the fabricated coating displayed the highest average microhardness (883 ± 37 HV) and the lowest mass wear rate (0.061 mg mm−1) without pores. The combined strengthening effect of fine grain strengthening and solid solution strengthening, as well as good formability, were the fundamental reasons for the high hardness and wear resistance of the coating. The results of this study can provide an experimental basis for the DLD alloy coatings with high hardness and wear resistance.

Additive manufacturing of functionally graded stellite6/17-4 PH fabricated via direct laser deposition

Multi-material structures with variable functionalities can lead to unique solutions for engineering problems compared to single-material structures. Additive manufacturing of Functionally Graded Materials (FGMs) using Direct Laser Deposition for the multi-material deposition of Stellite6 and 17–4 PH stainless steel has been investigated in this study. Process parameter design was successfully applied to achieve FGM structures with expected composition ratio and defect free. Results revealed that clads with insufficient laser power had unmelted 17-4 PH powders, while those with excessive power resulted in micro-cracks and disrupting the expected composition for the previous layer. Energy Dispersive Spectroscopy analysis results showed that the composition was almost as expected, with less than 10% deviation. The Stellite6 composition in FGM exhibits a minimum ratio near the substrate due to the penetration of 17-4 PH elements. Meanwhile, in multi-track clads, the Stellite6% decreases along the transverse direction due to increased heat input, multiple cladding tracks, higher dilution, and slower solidification rate. The results of the micro-hardness tests illustrated the gradual evolution of micro-hardness along the build direction starting from the base metal, which had a hardness of approximately 300 HV for 17-4 PH and for the compositions of 25%, 50%, 75%, and 100% Stellite6 showed increases of 10%, 39%, 43%, and 63% respectively, reaching up to 490 HV for fully Stellite6 at the top of the specimen.

Online Measurement of Melt-Pool Width in Direct Laser Deposition Process Based on Binocular Vision and Perspective Transformation.

Direct laser deposition (DLD) requires high-energy input and causes poor stability and portability. To improve the deposited layer quality, conducting online measurements and feedback control of the dimensions, temperature, and other melt-pool parameters during deposition is essential. Currently, melt-pool dimension measurement is mainly based on machine vision methods, which can mostly detect only the deposition direction of a single melt pool, limiting their measurement range and applicability. We propose a binocular-vision-based online measurement method to detect the melt-pool width during DLD. The method uses a perspective transformation algorithm to align multicamera measurements into a single-coordinate system and a fuzzy entropy threshold segmentation algorithm to extract the melt-pool true contour. This effectively captures melt-pool width information in various deposition directions. A DLD measurement system was constructed, establishing an online model that maps the melt-pool width to the offline deposited layer width, validating the accuracy of the binocular vision system in measuring melt-pool width at different deposition angles. The method achieved high accuracy for melt-pool measurements within certain deposition angle ranges. Within the 30°-60° measurement range, the average error is 0.056 mm, with <3% error. The proposed method enhances the detectable range of melt-pool widths, improving cladding layers and parts.

Assessment of structural defects and mechanical characteristics of IN718/St6 functionally graded material produced by direct laser deposition

Functionally graded materials (FGM) do not show special processing in the composite structure due to the combination of mechanical, thermal, magnetic and stress gradient properties. The aim of this study is to produce IN718/St6 FGM samples by direct laser deposition method. The product of this model should enable the development of mechanical products. Best of all, this can be done without significant reduction in texture and case to residual stress that are a consequence of rapid changes in mechanical and thermal properties in non-FGM samples. To fabricate part, direct laser deposition system equipped with a 1 kW continuous fiber laser is used, SEM/EDS analysis and microhardness testing to measure porosity, chemical composition, and quantify gradient mechanical properties is used. In this study, the cladding composition is selected from 100% IN718 to 100% St6 with a 25% change in St6 composition. To prevent the formation of defects, both single-parameter modes and individual layering are examined, considering the diverse nature of the combination. The result shows that using an individual layering structure, reduces 100% Lack of fusion defects in the IN718/St6 structure. EDS analysis confirmed that the St6 content gradually increased from the first to the fifth layer. The substrate hardness gradually increases from 200 Vickers hardness to 550 Vickers hardness, showing an almost linear trend. Moreover, by using individual layering, the coaxial structure is reduced by 55% and the relative orientation of the vertical line is reduced by 18° compared to using the St6 directly (non-FGM).

Analysis of structure and strength properties of heat‑resistant iron‑chromium‑nickel (Inconel 718) alloy obtained using secondary metal powder composition in direct laser deposition

This work presents investigations on the structure, chemical analysis, and strength properties of deposited metal using two types of metal powder compositions, namely the primary powder and the residuals (secondary) of the heat‑resistant ironchromium‑nickel alloy Inconel 718.Based on the obtained results, the causes of the formation of a fine‑cellular‑dendritic directional structure with needle and dendritic morphology were determined, as well as the decrease in heat resistance of the deposited material from the secondary powder of the heat‑resistant iron‑chromium‑nickel alloy Inconel 718 at elevated temperatures.

Prediction of solidification structure in the laser metal deposition of IN625 superalloy using the numerical and experimental techniques

Extensive research has been conducted in the field of direct laser deposition (DLD) process simulation. In this study, the finite volume method was used to predict the solidification microstructure and melt pool status in the IN625 cladding process. By fitting the data and matching the Hunt-Fleming relationship, the values of a=29.1827 and n=0.354 were obtained. A columnar structure was observed near the G/R=1.4e6 line, a combination of columnar and equiaxed structures between the G/R=1.4e6 and G/R=0.3e6 lines, and a fully equiaxed structure at points below the G/R=0.3e6 line. Finally, using the RSM method, a suitable area for achieving directional solidification (columnar dendrite with minimum orientation), with a power of more than 225 W and a powder/scan speed ratio (F/S) of less than 40 mg/mm, was determined.

Phase transformation behavior and mechanical properties of NiTi shape memory alloys fabricated by directed laser deposition

Directed laser deposition shows promise as a method for fabricating complex structure NiTi shape memory alloy parts in engineering, aerospace, automobile, and biomedical fields. The dislocation density has an impact on phase transformation behavior and mechanical properties of NiTi manufactured by directed laser deposition. In this work, NiTi samples were produced by directed laser deposition, and the mechanism of martensitic phase transformation and its interactions with dislocation density were revealed through molecular dynamics. Laser power and scanning speed are the main factors affecting dislocation density, the phase compositions of the samples are B2, B19′, and Ti2Ni phase, and the samples with dislocation density below 2 × 1015 m−2 show single-step B2–B19′ martensitic transformation, stress plateau and improved elongation, the samples with dislocation density above the value exhibit no significant transformation peak and no stress plateau. The movement of (100) twin planes and the growth of advantageous variants are observed in the simulation which can explain stress-induced martensitic reorientation and the stress plateau phenomenon. The bending test suggested that the sample under the optimal parameters has an 85 % recovery ratio within 8 % pre-strain.

Cracking Behavior of the ZhS6K Superalloy during Direct Laser Deposition with Induction Heating

For this work, the behavior of the ZhS6K alloy (Russian grade) in the process of direct laser deposition was investigated. Two samples, a “small” one (40 × 10 × 10 mm3) and “large” one (80 × 16 × 16 mm3), were fabricated with direct laser deposition. In both samples, the typical dual-phase γ/γ҆ microstructure with cuboidal shape of the γ҆ precipitates was observed. Both specimens revealed a similar tendency to continuous increasing in hardness from the bottom to the top associated with the refinement of γ҆ precipitates. The “small” sample was essentially crack-free, while the “large” one underwent extensive cracking. The possible effects of various factors, including thermal history, size, and shape of the gamma grains, on cracking behavior were discussed.

Combination of MSC Marc and SE-FIT to simulate the direct laser deposition of the multi-layer Ti–6Al–4V

Modeling the impact of a laser heat source on Ti6Al4V deposition is crucial for optimizing additive manufacturing, particularly in multi-layer contexts. This modeling provides insights into the material’s behavior during the Ti6Al4V manufacturing process. In this study, simulations using MSC Marc were conducted to model the impact of a laser heat source on the deposition of the multi-layer Ti–6Al–4V (abbreviated as Ti6Al4V) using the Ti–6Al–4V metal powder, followed by SE-FIT simulation to characterize their deposition morphology. MSC Marc was utilized to simulate the impact of a laser heat source on the Ti6Al4V, with a focus on identifying the melting area. Thermal conductivity was represented in the form of a chart as a function of temperature. Next, the morphology after deposition was defined using SE-FIT based on volume and boundaries. In the MSC Marc numerical model, a combined heat transfer coefficient of radiation and convection was applied to the convective coefficient. In the section depicting the multi-layered deposition morphology, a laser with 750[Formula: see text]W power was utilized at a speed of 3.3[Formula: see text]mm/s. After simulation, the resulting layer height and appearance were compared with the literature for a 25-layer composite. The practical implications of this research extend to the broader field of laser-induced heat deposition on Ti6Al4V deposition, which has applications beyond titanium alloys. The findings may contribute to advancements in the design and manufacturing of various metal components, impacting industries such as automotive, electronics and energy.

NiCrBSi/WC Composite Claddings Processed on AISI 316L Steel Alloy by the Direct Laser Deposition Process: Studies on Dry Sliding Wear Behavior and Wear Mechanism Maps

Abstract This study presented the wear behavior of the NiCrBSi/WC composite claddings processed on an AISI 316L steel alloy substrate by laser cladding approach. The scanning electron microscope (SEM) morphology of the claddings has shown excellent substrate–cladding interface bonding, good WC particulate distribution, and no noticeable cracks and voids. The electron dispersion spectroscope (EDS) spectra have confirmed the presence of respective NiCrBSi alloy matrix and WC elements. The XRD spectra have identified various phases and compounds such as gamma-Ni, FeNi3, Ni3B, Cr23C6, Ni3Si, and W2C commonly in all the processed composite claddings. The microhardness of the claddings was measured between 791 and 1086 HV0.2 for increasing the reinforcement WC particulate percentage from 15 wt% to 60 wt%. It is about 470% surface hardness enhancement with the processed composite claddings compared with the substrate alloy. The reinforcement of WC from 15 wt% to 60 wt% with the composite claddings resulted in wear resistance enhancement from 21.85% to 60.64% and the coefficient of friction from 56.87% to 77.92% against the substrate. The wear-rate maps and their respective cladding's worn surface morphology have described the wear mechanisms typically as adhesive, abrasive, oxidation, and delamination. The wear mechanisms are mainly influenced by the WC particulate percentage. The increased WC particulate content has increased the dominance of the abrasive wear mechanism while reducing the window of the adhesive wear mechanism. The windows of various wear mechanisms and their ranges, such as adhesive 0.0033 to 0.028, abrasion 0.010 to 0.067, oxidation 0.012 to 0.093, and delamination 0.015 to 0.120 mm3/m, for NiCrBSi/WC composite claddings comprehensibly represented the wear behavior for the varied conditions of dry sliding wear parameters.

Commercial-Grade Dielectrics Surface Metallization by Direct Laser Deposition from Deep Eutectic Solvents

Commercial-Grade Dielectrics Surface Metallization by Direct Laser Deposition from Deep Eutectic Solvents