Direct Laser Deposition Process Research Articles

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.

Evaluation of tribological behaviors of Inconel 625 cladding on same substrate cladded by direct laser deposition process

Evaluation of tribological behaviors of Inconel 625 cladding on same substrate cladded by direct laser deposition process

The Relevance of Process Parameter Optimization and Geometric Figure for Direct Laser Deposition of Inconel 738 Alloy and Its Theoretical Modeling

In order to minimize the gaps between the direct laser deposition channels and improve the quality and performance of the formed parts, the process of direct laser deposition is utilized in laser additive manufacturing to create sequential, single- and double-channel deposition layers on 304 stainless steel plates. Under the premise of keeping the layer rate and defocusing amount unchanged, this study investigates the effects of laser power, scanning speed, and powder feeding rate on the morphology and inclusions of single- and double-channel deposited layers. The aim is to determine the optimal process parameter values for direct laser deposition of single-layer, single-channel Inconel 738. The effects of the three process parameters on the response values were investigated using a multi-factor, multi-level experimental design. The evaluation indexes for the analysis included the deposited layer wetting angle and aspect ratio. The analysis involved one-way extreme analysis and ANOVA analysis. The optimal process parameters are a laser power of 550~750 W, a scanning speed of 7~13 mm/s, and the powder feeding rate was 2.1~4.33 g/min. At the same time, the relationship between surface tension and gravity was integrated with the spherical coronal model and Young’s equation to develop a mathematical model of the direct laser deposition process at a theoretical level. The mathematical model of the direct laser deposition process was utilized to analyze the correlation between the geometric parameters of the cross-section of the deposited layer. This analysis provides a valuable data reference for future Inconel 738 direct laser deposition.

Fabrication of TiB whiskers reinforced Ti6242 matrix composites by direct laser deposition: Powder preparation, microstructure and mechanical property

Direct laser deposition (DLD) technique has great potential in manufacturing titanium matrix composites (TMCs) components with complicated shape. The TiB whiskers reinforced Ti6242 matrix composites were fabricated from the premixed TiB2/Ti6242 powders via DLD technique. Quantitative characterization of the extent of mixing uniformity and the deformation rate of the ball milled TiB2/Ti6242 powders was performed so as to select the optimal ball milling parameters. The TiB2/Ti6242 powders with two different weight fractions of TiB2 (2 wt%TiB2/Ti6242 and 5 wt%TiB2/Ti6242) were used to obtain different distributions of TiB whiskers in the composites due to the change in the solidification path in DLD process. The TiB whiskers in the TMCs-Ⅰ obtained from the 2 wt%TiB2/Ti6242 powders exhibited a discontinuous network structure following solidification in hypoeutectic zone, while the TiB whiskers were randomly distributed in the TMCs-Ⅱ obtained from the 5 wt%TiB2/Ti6242 powders due to the solidification in hypereutectic zone. In comparison with the DLDed Ti6242, the α colonies and β grains of the TMCs-Ⅰ and TMCs-Ⅱ were significantly refined. In addition, both equiaxed and lamellar α phase were formed in the TMCs-Ⅱ, in which various orientation relationships (ORs) between TiB and α phase occurred and the presence or absence of OR between TiB and β phase was responsible for the different morphologies of α phase. The yield strength of the DLDed TMCs-Ⅰ and TMCs-Ⅱ increased by 10.7 % and 38.8 % in comparison with that of the DLDed Ti6242, and both the load-bearing strengthening and fine-grain strengthening effects effectively enhanced the strength of the composites.

Effect of temperature step on selection strategy of deposition head lift height and manufacturing stability during the direct laser deposition process

Based on the layer by layer cladding characteristics of the direct laser deposition (DLD), the optimal selection strategy of deposition head lift height is one of the effective methods to maintain the manufacturing process stability, improve product quality, and reduce complex post-process. However, owing to the temperature step caused by changeable layer residual temperature, the selection of deposition head lift height becomes extremely complex. In this paper, to clearly analyze the effect of temperature step on selection strategy of deposition head lift height for the DLD multilayer deposition process with a 1.85 kW fiber laser and a coupled coaxial four-channel nozzle, a semi-theoretical model considering the main physical phenomena involved in DLD process is proposed, validated, and applied. Here, working plane position, deposition head lift height, and step of residual and preheating temperature are considered as input process variables while manufacturing stability and error are determined as process responses. Results show that without considering the temperature influence, the final manufacturing stability can be achieved by ensuring that the distance between the deposition head and the initial working plane is less than the maximum relative distance corresponding to the selected deposition head lift height. When the layer residual temperature is considered, the single-layer cladding height steps positively, which makes the extreme working plane position positively migrated, and the manufacturing stability is also further enhanced. However, due to the migration of the finally stable working plane position, the manufacturing errors are also conditionally changed. Finally, in order to obtain an optimal manufacturing process, for any DLD process where the initial working plane position has been determined, the deposition head lift height should be selected slightly smaller than the single-layer height corresponding to that determined plane under residual temperature condition (hTr,Si), otherwise the manufacturing process will gradually lose stability and lead to fabrication failure.

Ambient and high temperature tensile behaviour of DLD-manufactured inconel 625/42C steel joint

In recent years, much attention has been directed towards multi-material systems produced using additive manufacturing technologies. Especially directed energy deposition-based systems provide a powerful tool for relatively simple production of components with controlled chemical composition in certain directions and locations. In this contribution, the potential of bimetallic material manufacturing based on the combination of nickel alloy Inconel 625 and 42C steel using direct laser deposition process was investigated. The monolithic single material blocks as well as graded blocks with alternate material deposition order were produced and investigated via light and scanning electron microscope. In addition, the miniaturized tensile tests at ambient and high temperatures were performed. It was observed that the character of two-material joint changed with the order of deposited materials. Based on the maps of chemical composition, it was shown that joint Inconel 625 to 42C was rather gradual, while 42C to Inconel 625 had sharp distribution of the main elements around the fusion line. The tensile test results demonstrated that the location of preferential failure was the joint itself in the case of gradual interface regardless of the test temperature. On the other hand, the sharp joint failed within Inconel 625 material at room temperature, while at elevated temperature the failure was observed in 42C steel region.

Distribution of microstructure, elastic modulus and residual stress near the interface in laser repaired GH4169 superalloy

As an emerging additive manufacturing technology, Direct Energy Deposition (DED) shows great potential for repairing or remanufacturing high-value components, such as aero-engine turbine blades. Through the utilization of Direct Laser Deposition (DLD), a specific form of DED, GH4169 superalloy powder can be cladded onto a GH4169 substrate to mimic the repairing of aerospace components. The microstructure, mechanical properties, and their distribution characteristics near the interface under different DLD process parameters are comprehensively studied. Combining Electron Backscatter Diffraction (EBSD), data stitching technique, and first-principles, the grain orientation and the elastic stiffness matrix of each phase are determined, based on which the distribution of elastic modulus and residual stress in a relatively large and complex area are analyzed. The results indicate that the DLD process parameters, such as linear energy density, significantly affect the grain size, grain growth direction and residual stress, but much less on the elastic modulus. Furthermore, the microstructure presents significant nonuniformity near the interface, and the elastic modulus presents anisotropy at the microscale, but almost isotropy at the macroscale, without noticeable value differences among the cladding zone, the heat-affected zone (HAZ) and the substrate. This study could shed light on the DLD process optimization for improving the microstructure and mechanical properties of laser-repaired components.

Investigating the solidification microstructure of IN625 superalloy cladded by direct laser deposition process on IN713LC

Investigating the solidification microstructure of IN625 superalloy cladded by direct laser deposition process on IN713LC

A Review on Direct Laser Deposition of Inconel 625 and Inconel 625-Based Composites—Challenges and Prospects

The direct laser deposition (DLD) process has seen rigorous research in the past two decades due to its ability to directly manufacture products followed by minimal machining. The process input variables play a vital role in determining the properties achieved in the products manufactured by the DLD method. Inconel 625, a nickel-based superalloy with exceptional mechanical performance and corrosion resistance, has been used in critical applications within the aerospace, process, and marine industry. However, its poor machinability and higher load requirements for plastic deformation have been challenging for manufacturers. Therefore, many studies have explored the additive manufacturing of Inconel 625 to overcome these problems. This article focuses on the DLD of Inconel 625 and its composites, presenting the state-of-the-art, drawing a relation among laser processing parameters and resulting material properties, microstructure and phase evolution, and the high-temperature performance of DLD Inconel 625. The paper highlights the areas on which further studies may focus.

Разработка технологии прямого лазерного выращивания крупногабаритных изделий атомной энергетики

The main advantages of direct laser deposition (DLD) of large-sized products are discussed on the example of the internal core baffle of a pressurized water reactor (VVER core baffle). The problem of product damage during operation as a part of reactor was considered. Powder materials of stainless steel with Russian grades 08Cr18Ni10Ti and 10Cr16Ni25MoTi were produced to develop the DLD process. Optimization of the core baffle design was carried out to improve operating reliability. Samples and fragments of the core baffle were manufactured by DLD method with complex research and tests. The concept of an experimental DLD unit for large-scale parts were developed.

Influence of Latent Heat of Fusion on the Melt Pool Shape and Size in the Direct Laser Deposition Process

The melt pool calculating method is presented based on the solution of the heat conduction problem in a three-dimensional formulation, taking into account the latent heat of fusion and the change in thermophysical properties with temperature. In this case, the phase transitions of melting and crystallization are accounted for using the source method. Considering the latent heat of fusion in the heat transfer process leads to melt pool elongation, as well as to a slight decrease in its width and depth. Depending on the mode, the melt pool elongation can be up to 22%. The penetration depth is reduced by about 5%. The deposition width does not change practically. The presented model was validated by comparing the experimentally determined melt pool shape and its dimensions with the corresponding theoretically calculated results. Experimental data were obtained as a result of coaxial video recording and the melt pool crystallization. The calculated form of the crystallization isotherm changes from a U-shape to a V-shape with an increase in the power and speed of the process, which coincides with the experimental data.

Mechanical and microstructural characterisation of Inconel 625 - AISI 431 steel bulk produced by direct laser deposition

The direct laser deposition process successfully produced a bulk material by mixing 50% Inconel 625 powders (M625) with 50% AISI 431 steel powders (M42C). The properties of this new material, such as tensile strength and wear resistance, were evaluated. The microstructure was also analysed using scanning electron microscopy. Moreover, the formation of defects and second phases in the bulk material were investigated by applying a tomography analysis. M625-M42C bulk material shows tensile strength and abrasive wear behaviour similar to Inconel 625 alloy, suggesting a potential replacement material for the more expensive Inconel 625. This study is focused on an innovative material, which had not yet been produced as a bulk, allowing the evaluation of the mechanical and metallurgical characteristics promoted by this mixture of powders. In addition, this deposition methodology seems very interesting for cladding or repair objectives since the failure did not happen at the transition interface between deposited bulk and substrate.

Numerical study on heat and mass transport phenomena during a multilayer cladding process for direct laser deposition

During the direct laser deposition (DLD) manufacturing process, complicated cladding process, and multiple thermal cycles lead to changeable transport phenomena and solidification behavior in the melt pool, which significantly affect the evolution of the structure and properties of part. Clarifying the process mechanism of the DLD process is of great value for further promoting its application service, and the development of an accurate and robust layer cladding model is obviously the key point. In this study, a three-dimensional numerical layer cladding model consisting of coupled heat transport and fluid flow, layer cladding and interface capture is developed and validated. Then, the heat and mass transfer characteristics, as well as its formation mechanism in multilayer cladding process are investigated in depth. Results show that a smooth, continuous, equal height, and common width cladding layer is formed in any cladding layer. Under the effect of the asymmetric evolution in scanning direction, the sub-layer reverse scanning strategy can effectively improve the surface roughness reducing at the end of previous layer. Besides, the front layer residual heat has significant influence on the multilayer cladding process. When the melt pool expands, the maximum temperature and velocity increase sharply, but the average energy decreases. Furthermore, the layer evolution will enter quasi-steady state as the heat input and dissipation reach dynamic balance.

High-density direct laser deposition (DLD) of CM247LC alloy: microstructure, porosity and cracks

Nickel-based alloys are known as non-weldable materials due to their complex characteristics. Consequently, additive manufacturing of these alloys is particularly challenging. In this paper, the influence of process parameters on the porosity, crack formation and microstructure of additively manufactured CM247LC nickel-based alloy is analysed. The feasibility of the direct laser deposition (DLD) process to manufacture crack-free and low-porosity CM247LC samples is studied. CM247LC samples were built on Inconel 718 that has similar chemical composition, to form hybrid superalloy parts. It was shown that crack-free and high-density CM247LC samples can be obtained through DLD without significant substrate preheating for certain parameter combinations: laser power in the range of 800–1000 W and powder feed rates between 6 and 8 g/min. High-cost and complex preheating was avoided that was commonly reported as necessary to achieve similar densities. For hybrid parts, a large beam diameter and slow scan speeds were employed to achieve optimal conditions as it was evident from the achieved bonding between the Inconel 718 substrate and the deposited layers. It was observed that good bonding between the two materials can be obtained with laser power values between 800 and 1000 W, scanning speed higher than 300 mm/min and powder flow rates of 6–8 g/min.

Multi-scale simulation of microstructure evolution during direct laser deposition of Inconel718

As a free forming additive manufacturing technology for high performance metal parts, laser deposition manufacturing has a broad application prospect in aerospace and other fields. The solidification behavior and microstructure of molten pool determine the mechanical properties of the deposited parts. A multi-scale Cellular Automaton (CA)- Finite Element (FE) model is developed to simulate the microstructure evolution with different process parameters during the Direct Laser Deposition (DLD) process. Temperature data and solidification parameters under different process parameters are obtained by finite element method, which establish connections between macroscopic temperature field and microstructure simulation. In addition, the effects of different process parameters on dendrite morphology, element segregation and grain structure are investigated. The primary dendrite arm spacing (PDAS), Nb element precipitation and grain size all increase with the increase of laser power, which are caused by the decrease of cooling rate. Moreover, the trend of the simulated results of microstructure under various process parameters are consistent with the experimental results.

Investigation on layer variation behavior and process stability during direct laser deposition using a semi-theoretic analysis model

For the promising direct laser deposition process, clarifying physical mechanism, optimizing manufacturing quality and realizing process stability and controllability are the current research hotspots to further improve and popularize this technology. However, under the limitation of complex physical processes, the research on the process stability is relatively insufficient. Especially for large scale study, it is affected by the across scales process, and it is rarely investigated in the previous literature due to the complicated methodology. Here, based on model reliability validation, a semi-theoretic analysis model considering main physical phenomena in the direct laser deposition process is established. The influence of the matching degree of working plane, powder deposition nozzle, and laser beam on the layer variation behavior and process stability during single-layer cladding is investigated. Results show that when the working plane, laser focal plane, and particle focal plane coincide, a largest cladding height can be obtained. Furthermore, the manufacturing efficiency and process stability are obviously improved by the effective adjustment of the matching degree of laser and particle nozzle, such as the eccentricity of the laser and particle center, and the axis-symmetrical nozzle arrangement, while they are reduced with the eccentricity and symmetry angle increasing and the direction angle deviation.

In-situ layer-wise certification for direct laser deposition processes based on thermal image series analysis

In direct laser deposition (DLD) processes, process uncertainty leads to defects in the final product, which can significantly compromise product quality, mechanical properties, and reliability of the additively manufactured (AM) parts. Therefore, quality control and certification are of critical importance in the broader adoption of DLD processes. In-situ thermal history contains critical information of process quality and defect occurrences. This paper proposes a new layer-wise anomaly detection method for in-situ DLD process certification by leveraging thermal image series analysis. Image registration is leveraged to characterize the dynamics in the layer-wise thermal history, and Gaussian process (GP) models are used to characterize the variation component which is left unexplained by the image registration operation. Multiple new layer-wise features are extracted from the registration modeling and the GP models. Both a thin wall specimen and a cylindrical shaped specimen are used in the case study to demonstrate the effectiveness of the proposed method. When comparing with the benchmark method, the proposed method shows comparable results for the thin wall specimen, and it significantly outperforms the benchmark method for the cylindrical shaped specimen. In addition, the average computational time of the proposed method is significantly shorter than the average layer-wise build time, enabling the proposed method to facilitate in-situ anomaly detection and process control.

Modeling and Experimental Characterization of the Influence of the Discrete Axial Nozzle Exit Shape on the Powder Stream in the Direct Laser Deposition Process

Modeling and Experimental Characterization of the Influence of the Discrete Axial Nozzle Exit Shape on the Powder Stream in the Direct Laser Deposition Process

Large-eddy simulation of coaxial powder flow for the laser direct deposition process

We conduct a large-eddy simulation with Lagrangian particle tracking to study the coaxial powder flow for the laser direct deposition process. To our knowledge, this is the first numerical study in which the high-fidelity, eddy-resolving simulation approach is applied to this process. Via the eddy-resolving simulations, we show the instantaneous flow structures and the associated turbulent quantities in great detail during the development of the transient state. We examine the effect of the flow on the particles and the resulting distributions of particle positions on various horizontal planes. Moreover, we demonstrate how the particle velocities affect the particle temperatures. On assessing three settings of initial particle distributions, we find that the simulation assuming a parabolic distribution for particle velocities gives good predictions of particle velocities and temperatures that are consistent with experimental data. Finally, we examine the effect of a substrate by moving the bottom boundary to the point of intersection of the particle streams. We find that due to increased flow dissipation, the substrate raises the location of the interaction point by approximately 10%. Moreover, the resulting reduction in particle velocity slightly increases the particle temperature. These differences can lead to a quite different distribution of the powder stream and have a significant impact on the mass and energy balance of the cladding model depending on the spot size of the laser beam and powder stream.

Using a Trial Sample on Stainless Steel 316L in a Direct Laser Deposition Process

Direct laser deposition technology is used for the manufacture of large-size products with complex geometries. As a rule, trial samples with small dimensions are made to determine the deposition parameters. In order for the resulting products to have the required performance characteristics, it is necessary to minimize the number of internal macrodefects. Non-fusion between the tracks are defects that depend on the technological mode (power, speed, track width, etc.). In this work, studies have been carried out to determine the power level at which non-fusion is formed, dwell time between the tracks on the model samples. This paper considers the issue of transferring the technological parameters of direct laser deposition from model samples to a large-sized part, and describes the procedure for making model samples.