Laser Metal Deposition Method Research Articles

Direct formation of pure copper layer on aluminum nitride by multibeam laser deposition with blue diode lasers

A demand of power module devices has been increasing for highly energy efficient social system. The insulated heat sink printed circuit board is the key component of power module devices, which is composed of copper and aluminum nitride (AlN) due to high thermal conductivity. The conventional method of the joining between copper and AlN is active metal brazing method, but there is an issue that the high heat treatment of this method generates thermal residual stress on the board and decrease the reliability. For that reason, the development of a direct bonding process between copper and AlN has been demanded. Therefore, we focused on the laser metal deposition (LMD) method, which is a selective heating and microfabrication process. The LMD method is a method in which a powder material is supplied to the processing point and irradiated with a laser to melt the powder and form layer on the surface of the substrate. Then, a blue diode laser with a wavelength of 450 nm, which has a high absorptivity of 60% for copper, is used as a heat source. In addition, the multibeam type LMD system has been installed for the uniform heating of powder. In this study, the laser power density, laser scanning speed, and powder feeding rate were changed to explore the conditions for forming a copper layer on the AlN substrate.

Prevention of solidification cracking in alloy 718 additive manufacturing by laser metal deposition method based on control guidelines for weld solidification cracking

The chemical composition of alloy 718 powder was optimized to suppress a solidification cracking in the additive manufactured part by the laser metal deposition method. The relationship between the condition of additive manufacturing and defects was evaluated. A lack of fusion was observed on the low heat input (low energy density), and the solidification cracking occurred on the high heat input (high energy density). The powder composition of alloy 718 was attempted to be optimized from a theoretical approach of the solidification cracking susceptibility. It was found that Si and B had a significant influence on the solidification cracking, therefore a preventive powder with reduced Si and B was developed. The effects of Si and B on solidification cracking were compared by reproducing the solidification conditions during additive manufacturing and evaluating the solidification brittle temperature range (BTR) using the Varestraint test. It was found that the BTR of the preventive material was smaller, and the solidification cracking susceptibility was improved. In addition, the solidification cracking did not occur in additive manufacturing using the preventive powder. In other words, it is suggested that the countermeasure for weld solidification cracking leads to the prevention of solidification cracking in additive manufacturing directly, and the effectiveness of the optimization of powder composition was verified.

Elucidation and verification of cracking behavior in additive manufacturing of alloy 718 based on fractography

This study identified a cracking that occurred continuously in the built direction of an additive manufactured part of alloy 718 by the laser metal deposition method and clarified the cracking behavior. The solidification microstructure of alloy 718 was evaluated by EDS, EPMA, and extraction residue, and it was found that Laves phase, Ti carbides, and Al oxides were formed between the dendrite microstructures. A fracture surface analysis of the cracks revealed that the cracking in the additive manufacturing was hot cracking associated with the liquid film and that the cracking occurred along the grain boundaries. The fracture surface at the beginning of the cracking showed a solidification cracking fracture surface. The experimental investigation for crack propagation during additive manufacturing and the analytical evaluation of the mechanical state around the cracking using thermal elastic-plastic analysis elucidated the cracking behavior during additive manufacturing. If the cracking exists at the fusion boundary, it is suggested that the cracking initiates from the solid-liquid interface towards the solidification direction. Moreover, tensile strain occurred around the cracks during additive manufacturing, particularly the strain was biggest at the crack edge on the fusion boundary. Therefore, the continuous cracking that occurred beyond each layer in the additive manufacturing of alloy 718 in this study can be considered solidification cracking, and its behavior can be further explained as a notch extension cracking that starts from the solidification cracking and continuously occurs in the solid-liquid coexistence temperature region.

Highly ductile and mechanically strong Al-alloy/boron nitride nanosheet composites manufactured by laser additive manufacturing

Laser metal deposition (LMD) is one of the prospective additive manufacturing (AM) processes to fabricate metal-based nanocomposites. In this study, aluminum alloy (AlSi10Mg) was reinforced by boron nitride nanosheets (BNNSs) via LMD method. High speed ball-milling was used to mix AlSi10Mg powder with BNNSs at fraction range 0.05–0.2 wt%. Comprehensive morphology analysis as well as structure-property relations were investigated. The study showed that adding BNNSs into Al-alloy via LMD process not only promoted the hardness (40 %) and mechanical properties of the matrix (24 %, 100 % and 96 % increments in ultimate tensile strength, yield strength and Young's modulus, respectively), but also significantly improved its ductility (∼300 % increase). This has been observed clearly in fracture analysis where ductile fracture features were the dominant mode for all prepared samples. According to the observations by optical microscopy and electron backscattered diffraction, BNNSs have a crucial effect on grain refinement; grain size reduced from ∼30.4 to 17.5 μm upon the addition of 0.2 wt% of BNNSs. In addition, during LMD process, hard mesophase of aluminum nitride was formed which assisted BNNSs in reinforcing the Al-alloy. The results helped to understand the microstructure changes and mechanical properties improvements when LMD method was used.

High speed coating for pure copper by multi-beam laser metal deposition method with high intensity blue diode lasers

Copper is expected to have many applications due to its virus inactivation properties, but it has been difficult to produce a thin layer with high bonding strength. A multi-beam blue diode laser installed laser metal deposition (B-LMD) system was newly developed with a laser intensity of 4.7 × 105 W/cm2, which is improved about five times higher than that of conventional systems. Using this system, we demonstrated the high-speed formation of a pure copper layer on a stainless steel type 304 (SS304) circular tube. A pure copper powder and the blue diode lasers were simultaneously supplied to a SS304 circular tube, and the powder was melted and solidified to form a pure copper layer on it. As the result, the laser intensity was increased with increasing layer formation efficiency, and at the laser intensity of 4.7 × 105 W/cm2, the maximum value of layer formation efficiency was obtained at the peripheral speed of 400 mm/s. Moreover, it was revealed that the dilution length was decreased with increasing peripheral speed, the minimum value of 3 μm at the peripheral speed of 400 mm/s was obtained.

Effects of scanning pattern and laser power reduction in stainless Steel 316L additive manufactured by direct laser metal deposition

The major purpose of this study is to investigate two strategies for additive manufacturing processes of SS316L using the direct laser metal deposition method (DLMD). In additive manufacturing (AM), the influence of scanning patterns was the first strategy, and the other strategy was the effects of laser power reduction in various layers. The experiments used a semiconductor diode laser with a coaxial nozzle head. The goal of this study was to determine how these two techniques influenced the properties of additive-produced components. Geometrical metrics such as width, height, and penetration, as well as particle size, and microhardness profiles, were assessed in the macrosection of the fabricated wall samples. The sample’s height stability was also investigated. The results revealed that the scanning pattern significantly affects all aspects of additive-manufactured components. The results indicated that higher stability is achieved when using a unidirectional scanning sequence. The average particle size of specimens obtained using the unidirectional and bidirectional scanning patterns was 8.6 and 9.69 μm, respectively. The pattern of particle size variation in the samples demonstrates that the LMD walls in the beginning and end are larger than in the samples at the center, the microhardness fluctuation pattern is in the opposite direction of particle size. The width of the samples was also found to decrease as the laser power was reduced from the substrate upward.

Microstructural and mechanical characterization of parallel layered WC- NiCr weld overlay on 080 M40 steel substrate prepared using additive manufacturing

080 M40 Medium carbon steel has potential applications in axles, shafts, bolts, studs, spindles, automotive components and many more. In high friction applications these steels possess better wear resistance, and after weld overlay, they can exhibit superior properties. Additive manufacturing (AM) is an advanced method in which material in the form of powder or wire is used to form a desired shape. Laser Metal Deposition (LMD) is an AM method which is used in industrial application to recreate, repair and produce corrosion resistance weld overlay on a part. In comparison with conventional overlay techniques such as Plasma Transfer Arc (PTA), Metal Inert Gas (MIG) & Tungsten Inert Gas (TIG); Laser weld overlays are faster techniques which can make thin sections with good metallurgical bond and with high productivity and flexibility. Apart from that it has also advantage of low heat affected zone, minimum metal dilution, and can produce thin layers with good aesthetics. In this paper, 080 M40 steel samples were used as substrate and WC- NiCr powder was weld overlayed using LMD method. Such kind of weld overlays will be had potential application in the field of mining. The weld overlay was deposited in parallel layered fashion and effect of set of parameters like feed rate, dilution, size of the bead and processing speed were used to produce weld overlays of 1 mm thickness. metallurgical, micro structural and mechanical properties of these weld overlay materials have been investigated. These properties are very important in the processing of mining tools as well as other parts produced using the LMD process and also for other future applications. Further effect of laser processing parameters on the resulting properties of these steels weld overlays are discussed.

Numerical analysis of statically indeterminate structure with repaired layer by transfer matrix method

In recent years, the aging of infrastructure facilities, such as power generation and chemical plants, has been a serious social problem. When defects are detected by the inspections, it is required to repair them. Our research group have developed the advanced repair technique using the laser metal deposition method. In the future, it will be necessary to clarify how the repair process applied to a part of component affects the deformation behavior and stress on the whole structure. In this study, we develop the methodology to analyze the repaired structure using the transfer matric method, which has been developed in our research group. Firstly, we extended fundamental theory to that for the repaired element, and converted into a code based upon Python language. In order to check the verification, some examples of statically indeterminate structural with the repaired part were solved.

High-temperature tensile and fatigue strength properties of stainless steel repaired by laser metal deposition method

High-temperature tensile and fatigue strength properties of stainless steel repaired by laser metal deposition method

Pure copper rod formation by multibeam laser metal deposition method with blue diode lasers

Pure copper rods were additively fabricated by using a multibeam type laser metal deposition (LMD) device equipped with two blue diode lasers, and the influence of them on the rods was investigated. It is unknown how the rod changes with respect to the process parameters such as the laser power and the powder feeding rate. In this study, the laser power and the powder feeding rate were changed to form a pure copper rod in the LMD method, and the influence of them on the cross-sectional area of the rod was investigated. Moreover, the electrical resistance value of the rod was measured, and the influence of the laser power on the electrical resistivity was investigated. In addition, the elemental analysis of the cross section was performed by an electron probe microanalyzer, and the influence of the laser power was investigated. As a result, the cross-sectional area of the rod is slightly dependent on the powder feeding rate, and even if the powder feeding rate is increased, the cross-sectional area is slightly increased, but when the laser power is increased, the cross-sectional area is significantly increased. Moreover, when the laser power was increased, the electrical resistivity increased. The elemental analysis revealed that the surface of the rod might be oxidized, which suggested that it affected the electrical resistivity.

Additive manufacturing of stellite 6 superalloy by direct laser metal deposition – Part 2: Effects of scanning pattern and laser power reduction in differrent layers

In this study, the purpose is to investigate two strategies for direct laser metal deposition method (DLMD) additive manufacturing of stellite 6 Cobalt-based superalloy experimentally. The first one was the effect of scanning pattern, and the second one was the influence of laser power reduction in different layers in additive manufacturing (AM). For the experiments a coaxial nozzle head coupled with a 1 kW continuous fiber laser was used. This research aim was to examine the effect of these two strategies on characteristics of the additive manufactured components. The macro section of the geometrical dimensions, including height and width, profiles of microhardness, grain size, and microstructure of the 3D printed wall samples were investigated. The height stability of samples was also examined. The results indicated that scanning pattern has an important role in all the additive manufactured components features. Results show that when the unidirectional scanning pattern was used, the more stability will be obtained. The average grain size of samples which were produced by unidirectional scanning pattern and bidirectional scanning pattern was 2.25 μm and 2.83 μm, respectively. The trend of changes in the grain size of the samples shows that the beginning and the end of the LAMed wall are larger than the sample’s center, and the trend of the microhardness variation is in reverse regime of the grain size. Also, it was shown that with decreasing the laser power from the substrate upwards, the width of samples has reduced.

Investigation microstructure and fracture behavior of welded stainless steel specimens previously obtained by supersonic laser deposition

Stainless steel 316 L specimens, previously deposited by supersonic laser deposition, were welded by laser metal deposition method (SLD_W_LMD). The issues of structure formation in deposited SLD samples with additional laser processing were considered. The microstructure and mechanical properties of the specimens, the metallurgical anisotropy between powder particles and gradient structure of SLD_W_LMD specimen was investigated. The microhardness of specimen obtained by SLD higher into 1.7 times compare SLD_W_LMD specimen. It is shown that the hardness of the SLD samples is achieved due to the partial preservation of the initial powder particles. Tensile strength SLD_W_LMD specimen higher into 1.14 times comparison to specimen obtained by SLD. The relative deformations of the specimen SLD_W_LMD are 1.5 times higher than that of the SLD samples. These results are achieved due to good metallurgical contact between powder particles, which is achieved due to laser influence.

Additive manufacturing of stellite 6 superalloy by direct laser metal deposition – Part 1: Effects of laser power and focal plane position

This paper surveys the additive manufacturing (AM) of stellite 6 Cobalt-based superalloy by direct laser metal deposition method (DLMD) experimentally. In the present research, a coaxial nozzle head coupled with a continuous fiber laser with a maximum power of 1 kW was used. The purpose of the current research is investigating two strategies for DLMD additive manufacturing; the first one was changing the focal plane position of the laser beam inside the powder stream, 4 mm above and 4 mm below the powder concentration plane, and the second one was investigating the variation of the laser power (100–300 W). Some characteristics such as the geometrical dimensions (height and width), microhardness profile, grain size, and microstructure of the 3D printed wall samples were studied. The stability of the additively manufactured wall in terms of height was investigated. The results indicated that locating the focal plane position above the substrate, led to the more interaction area between the laser beam and powder stream and caused the higher height of the AMed wall. Results showed that when the focal plane position is near to the powder stream focus, the more stability will be obtained. By locating the laser spot point 2 mm above the powder concentration plane, better stability achieved. Increasing the laser power has a reverse effect on the height and stability: the more laser power, the higher height of the AMed wall, and the less stability observed. Results indicate that the laser power of 100 and 150 W has the highest height stability. The trend of changes in the grain size of the samples shows that the beginning and the end of the AMed wall are more significant than the sample’s center and the trend of the microhardness variation is in a reverse regime of the grain size. Also, the average grain size will be increased when the laser power increased. The largest and the smallest average grain size are 3.13 μm and 2.11 μm for the highest and the lowest laser power, respectively.

Distortion compensation in LMD process

This article describes the gist of laser metal deposition method and general stages of part buildup. Further it clarifies the shrinkage negative influence on wall forming in LMD process. The types of the part deformation on the example of thin walled shell presented. The methods of compensating the deformation influence on the part geometry are proposed.

Rapid construction of multicomponent TRIP stainless steel by powder feeding laser deposition for comprehensive properties

This study developed a powder feeding laser metal deposition (LMD) method that can be used to achieve a layer-by-layer fabrication of component grade material for efficiently screening the properties of different chemical compositions and determining the optimized composition range for TRIP stainless steel. The 13Cr-xNi-(10-x)Mn-3Al steel with continuous graded composition was produced by the LMD method. An optimized composition range for TRIP stainless steel was determined by testing the properties including hardness, austenite content and surface potential of positions with different compositions. The suggested Ni content is between 3%–6% and Mn content is between 4%–7%. This study demonstrates the potential of LMD method to accelerate the development of steel economically.

Study on high temperature strength characteristics of material repaired by laser metal deposition method

Study on high temperature strength characteristics of material repaired by laser metal deposition method

Structure features of the composite materials Inconel 625/TiC, produced by LMD method

In this paper, the metal composite material Inconel 625/TiC with 20 % carbide content produced by laser metal deposition (LMD) method was investigated. The initial powders were in three various states: they were fed from single flasks; they were previously mixed in a gravitational mixer or in a planetary ball mill. It was shown that only composites obtained from the powders previously mixed in a planetary ball mill had no cracks. At usage the powder in another states, grown composites had magistal cracks. When cracks did not arise, the carbide particles TiC had initial spherical shape and initial composition. In those cases when cracks appeared, the carbides have dendritic shape, and their composition are changed. Investigation of the powder materials showed that during mixing the individual particles of the Inconel powder are covered with layer of titanium carbide. As a result, the thermophysical properties of Inconel powder are changed, and an energy required for recrystallization of the Inconel powder is increased.

Investigation on the process and microstructure evolution during direct laser metal deposition of 18Ni300

PurposeAdditive manufacturing is a fabrication technology with flexibility and economy. 18Ni300 is one of maraging steels with ultra-high strength, superior toughness, so it is an excellent candidate of structural material. This paper aims to explore the feasibility of using direct laser metal deposition method to fabricate18Ni300, and the evolution of its microstructure and defects is studied.Design/methodology/approachThe experiments were conceived from single-trace-single-layer (STSL) test to multi-trace-multi-layers (MTML) test via single-trace-multi-layers (STML) test. The microstructure, defects and mechanical properties were analyzed.FindingsThe STML results showed that the columnar/equiaxed transformation occurred at the top part and the grain size increased with the layer number increasing, and it was explained by an innovative attempt combining columnar/equiaxed transformation model and the change of grain size. The MTML test with the interlayer orthogonal parallel reciprocating scanning pattern resulted in the grain growing along orthogonal directions; with the increase of overlap rate, the length and the area of the columnar grain decreased. What is more, the later deposition layer had lower micro-hardness value because of heat history.Originality/valueDirect laser metal deposition method was a novel additive manufacturing method to manufacture 18Ni300 components, as 18Ni300 maraging steel was mainly manufactured by selective laser melting (SLM) method nowadays. It was useful to manufacture maraging steel parts using direct laser deposition method because it could manufacture larger parts than SLM method. Influence of processing parameters on forming quality and microstructure evolution was studied. The findings will be helpful to understand the forming mechanism of laser additive manufacturing of 18Ni300 components.

Evaluation of microstructure, microhardness, and electrochemical properties of laser-deposited Ti-Co coatings on Ti-6Al-4V Alloy

The marine, aerospace, and power machinery industries show progression in the application of titanium alloy components due to their good properties. However, the alloy exhibits poor thermal stability, low hardness, and poor tribological properties; as a result, the use of Ti6Al4V in various industries is restricted. Consequently, a search for surface improvement of Ti6Al4V alloy arose with the intention of enhancing its endurance. The use of laser metal deposition method by integrating chemical barrier coatings is considered as advantageous; therefore, an investigation aimed at surface improvement of Ti6Al4V by incorporation of Ti-Co coatings developed. To fabricate the coatings, a 3-kW continuous wave ytterbium laser system (YLS) was used, and to control the movement of the cladding process, a KUKA robot was attached to the system. The microstructure, corrosion, and mechanical properties of the titanium alloy-cladded surfaces were studied at different laser process parameters. To analyze the microstructure of the cross section, optical and scanning electron microscopy were employed. A laser power of 750 W and scanning rate of 1.2 m/min were found to be the optimum process conditions for a 60Ti-40Co alloy. When comparing the mechanical properties of the alloy and bare substrate, the alloy exhibited a significant increase in terms of the hardness. It was found to have 719 HV as compared to 301 HV which is that of the substrate, this indicates to an increase of 58.14% in the hardness. Lower laser scanning rates result in a larger fraction of hard-intermetallic phases which in turn lead to coatings with enhanced hardness levels. Furthermore, the yield strength and tensile strength of the coatings increased to maxima of 2.30 and1.66 GPa, respectively in comparison to the substrate, due to the addition of Co. Additionally, the corrosion rates of all the coated specimens were reduced as a result of the oxide films formed on the laser-coated Ti6Al4V alloy samples.