Figure 4 - available via license: Creative Commons Attribution 4.0 International
Content may be subject to copyright.
![Solidification map; effect of temperature gradient and growth rate on the morphology and size of solidification microstructure [3].](publication/355787846/figure/fig1/AS:11431281093256882@1667148768688/Solidification-map-effect-of-temperature-gradient-and-growth-rate-on-the-morphology-and.png)
Solidification map; effect of temperature gradient and growth rate on the morphology and size of solidification microstructure [3].
Source publication
This study aimed to suggest a solidification map based on the solidification parameters G and R of each layer in the multilayer deposition for the investigation of heat accumulation on the deposit. Through the solidification map, the appropriate solidification conditions of the microstructure were determined. In order to investigate the solidificat...
Contexts in source publication
Context 1
... similarity between the simulation results and the thermal condition of the actual deposit indicates that the developed CMT-WAAM simulation model is suitable for calculating the solidification parameters. Figure 4 shows the solidification map, which can explain the effect of G and R on the microstructure formation. The temperature gradient (G), which is the y-axis of the map, is the rate of temperature change ( • C/mm) according to the distance at the solid-liquid interface, and the growth rate (R), which is the x-axis, is the speed at which the solid-liquid interface moves (mm/s). ...
Context 2
... solidification map is composed of a combination of G/R and G × R curves, where the G/R value affects the morphology of the microstructure, whereas G × R value affects the size of the microstructure [20,21]. As shown in Figure 4, a planar microstructure appears at high G/R values, and as this value decreases, the morphology transforms from cellular to cellular dendritic, columnar dendritic, and finally equiaxed dendritic. In addition, as G × R decreases, a coarse microstructure forms, whereas a fine microstructure forms as G × R increases. ...
Context 3
... G/R value affects the morphology of the microstructure, whereas G × R value affects the size of the microstructure [20,21]. As shown in Figure 4, a planar microstructure appears at high G/R values, and as this value decreases, the morphology transforms from cellular to cellular dendritic, columnar dendritic, and finally equiaxed dendritic. In addition, as G × R decreases, a coarse microstructure forms, whereas a fine microstructure forms as G × R increases. ...
Context 4
... properties such as the tensile strength and hardness of a deposit can be improved by forming a fine microstructure [22][23][24]. Figure 4. Solidification map; effect of temperature gradient and growth rate on the morphology and size of solidification microstructure [3]. Figure 5 shows the G, R, and G × R for each layer of the deposits. ...
Similar publications
The solidification cracking behavior in laser welds of steel/copper dissimilar metals was systematically investigated. T2 copper and SUS304 stainless steel were used in the study. The results showed that the occurrence of solidification cracking in welds was the synergistic effect of ε phase liquation, inclusions and composition segregation. During...
Citations
... It was reported that stable plane front solidification could be achieved under faster cooling rates and lower heat inputs. Park et al. [11] modelled the WAAM process to study the effect of heat accumulation on the cooling rates and the resultant microstructure. Jiong et al. [12] developed a 3D transient thermal model to study the variation in the thermal gradients in WAAM-built cylindrical thin-walled structures. ...
The wire arc additive manufacturing (WAAM) process is one of the fast emerging metal additive manufacturing techniques. WAAM is known for its high deposition rates and relatively lower costs, which makes it suitable for the fabrication of large parts. Heat accumulation is one of the key challenges with WAAM. As layers are deposited during WAAM, heat accumulates due to insufficient cooling. This continues as the number of layers increases, which affects the geometry and mechanical performance of the deposited part. In this study, the WAAM process is modelled numerically, and the heat accumulation patterns are analysed. The numerical results compare well against experimental observations available in the literature. Further, the influence of interpass dwell time on the accumulated heat is discussed through the quantification of heat.
... Most of these studies reported defected-free parts. The microstructure analyses showed that the deposited material mainly consists of layer band austenitic dendrites vertically oriented, with some ferrite and sigma phases [8][9][10][11][12][13][14][15][16]. Nonetheless, according to [12], the arc mode may lead to different grain morphologies, i.e. using the SpeedArc WAAM mode led to a finer solidification structure due to the lower heat accumulation and faster thermal cycles. ...
... Fig. 8e to 8h, which show the evolution of the microstructures inside the semi-elliptical morphology of the individual layers, from its top to its bottom, enable to observe columnar grains which grow perpendicularly to the fusion lines ( Fig. 8g and h). However, moving upward, vertically, inside the layer, it is also possible to observe a more equiaxed structure (Fig. 8f), which, according to references [10,33], results from the low temperature gradient inside of the molten pool. This assumption is corroborated by the temperature measurements performed in the current work, which shows that the layers close to the last to be deposited remain at very high temperatures (around 700 • C), during a longer period. ...
The use of 3D printed stainless steel requires a deep knowledge of its mechanical properties. This paper presents material characterisation of 316LSi austenitic stainless-steel coupons manufactured by CMT-WAAM, considering different deposition directions. The specimens were tested according to ISO 6892-1, the fractures surfaces were examined by SEM for machined and as-built conditions. The material was subject to hardness test and deep microstructural analyses, to assess the anisotropy in material properties at the micro and macro scales, respectively. A thermal analysis performed by infrared thermography of the material deposition in CMT-WAAM was also performed to establish the influence of the temperature evolution (versus time and position) on the microstructural and mechanical properties of the deposited walls. Finally, a statistical assessment was carried out, including results available in the literature and a material model available in the literature was adjusted to the test results, enabling to conclude that it is possible of accurately reproducing the uniaxial stress-strain behaviour, therefore providing a necessary input for the design of steel structures with 3D printed stainless steel.
... Additionally, simplifying robot operation and creating necessary software for expanding usage remain important concerns. Modern temperature control methods [7][8][9] require improvement and the possibility of integrating real-time telecommunications feedback systems [10], such as thermal cameras and thermal laser sensors, to address issues related to heat distribution among layers and methods of their overlap [11][12][13][14][15]. ...
The object of the research is the possibilities of using a wireless communication system for feedback to improve the additive manufacturing process of a part using the arc welding technology with temperature control for heat propagation. The problem to be addressed includes determining the geometric properties, print topology, and temperature control regimes for the mentioned part. It also involves the installation of telecommunications sensors and cameras for temperature monitoring, conducting simulation calculations using ABAQUS software, and physical experiments. The results of the work include simulating the additive manufacturing process at necessary hierarchical system levels, considering specific requirements and obtaining the required geometric dimensions. Residual stresses have been analyzed, software-related heat propagation issues have been discussed, the influence of cooling on production quality has been verified, and optimal print parameters have been created. Additionally, the potential use of a feedback telecommunication system with telecommunication devices such as cameras and laser sensors for temperature control has been explored. The obtained data has been used for the possibility of generating an automated program for robot control during the additive manufacturing process. Based on the data obtained, residual stress values and defects in the produced samples were determined. A real experiment was conducted, and the results of the real experiment were compared and analyzed. The assessment of the impact of the feedback telecommunication system on the additive manufacturing process using arc welding with heat propagation control through cooling periods in practice allows for improved printing quality, technology of the produced part, cost reduction, and speeding up the production process.
... Wang et al. [9] studied the microstructure, microhardness and tensile properties of a block of SS316L fabricated by WAAM and observed non-equilibrium microstructure across the overlapping and remelting zones. The heat accumulation as the number of layers increased led to remelting the previous layer, which affected the secondary dendrite arm spacing [10]. Chen et al. [11] observed the presence of δ, γ, and σ phases in WAAM-built SS316L. ...
... The presence of δ phase in austenitic stainless steels, even in small quantities, can minimize hot cracking and improve weldability [12]. However, during WAAM, the remelting at the layer interfaces re-dissolves the δ phase into austenite and forms an intermetallic σ phase [10], which is detrimental to the part's mechanical properties [13]. ...
This work investigates the fatigue crack propagation behaviour of stainless steel 316L depositions from wire arc additive manufacturing.
... With distance from the interface, both the G and R factors decrease further. However, since the value of the R experiences a further reduction [34], the value of the G/R decreases, and the morphology of the grains is equiaxed at the top of the coating ( Figure 9). Meanwhile, the lower heat input in the MT2 specimen creates a high G value and, of course, a very high R value at the interface of the coating. ...
Refractory high-entropy alloys (RHEAs) contain alloying elements with a high melting point, promising high-temperature applications due to their unique properties. In this work, laser cladding is used to prepare RHEAS based on NbMoTaTiNi. At the same time as laser cladding, the ultrasonic field is used, and then the microstructural characteristics, grain size, residual stress, wear, and hardness of the coating are evaluated. The results show that the coating is biphasic and includes the γ (Ni) and NbMoTaTiNi phase. The NbMoTaTiNi phase had a uniform distribution throughout the coating when the ultrasonic field was applied, so that when the ultrasonic field was not used, the NbMoTaTiNi powder, in addition to spreading uniformly, had the un-melting of large particles. This caused an increase in the residual tension of the coating. The conversion of columnar grains to the equiaxed, and the reduction in structural defects, were other characteristics of using the ultrasonic field. The formation of equiaxed grains with zigzag grain boundaries reduced the friction coefficient, wear volume loss, and the wear rate of the coating applied with ultrasonic.
... The metal powder used for the LMD process was a nickelbased superalloy Inconel 625 (Sandvik Osprey, England) with a 10,11 Because of Inconel 625's outstanding mechanical properties at high temperatures and stainless steel 316L's superior corrosion-resistant properties, the two materials are used together in building jet engines and exhaust pipes. [12][13][14][15] The chemical composition of the Inconel 625 powder and stainless steel 316L substrate is shown in Tables I and II each. ...
This study developed a deposition guideline that considered the effect of processing variables, such as laser power, on the deposition quality at various tilting angles of laser nozzle and substrate when fabricating components of complex geometries like overhang and curved structures with the multi-axis laser metal deposition process. The guideline was based on analyzing the effect of processing variables, namely, laser power, beam diameter, and specific energy, on the deposition quality under six spatial variables. Spatial variables were defined by combining the angle of the substrate to the ground (0°, 45°, and 90°) with the angle of the laser nozzle to the substrate (90° and 45°). The bead contact angle and dilution were used as indexes of the deposition quality evaluation. If both the ideal ranges of the evaluation indexes are satisfied, the deposited material can exhibit high surface quality and geometrical accuracy. To prevent excessive dilution caused by the widened and flattened deposit under tilted laser nozzle conditions, a larger beam diameter, when compared to the state where the laser nozzle is perpendicular to the substrate, should be used. For a situation where the effect of the gravitational force is dominant, such as the substrate perpendicular to the ground, the laser power and the specific energy should be controlled simultaneously to maintain the ideal contact angle and dilution. In addition, the effect due to the change in the amount of melted powder on the cross-section geometry caused by beam diameter variation should be considered for every tilted motion.
... Others studied the indication of comprehensive thermal characteristics of a WAAM process and pointed out the thermal effects on the geometrical accuracy, process stability, and deposited part properties. The deposited beads' temperature profile and the solidification parameters are examined using experimental and numerical simulation models that reflect the deposition process characteristics [22,[57][58][59]. Inconsistent layer cross-sectional dimensions and undulated surface appearance are two types of defects observed in WAAM products. ...
The wire arc additive manufacturing (WAAM) process is a 3D metal-printing technique that builds components by depositing beads of molten metal wire pool in a layer-by-layer style. Even though manufactured parts commonly suffer from defects, the search to minimize defects in the product is a continuing process, for instance, using modeling techniques. In areas where thermal energy is involved, thermomechanical modeling is one of the methods used to determine the input thermal load and its effect on the products. In the WAAM fabrication process, the thermal load is the most significant cause of residual stress due to the extension and shrinkage of the molten pool. This review article explores the thermomechanical effect and stress existing in WAAM-fabricated parts due to the thermal cycles and other parameters in the process. It focuses on thermomechanical modeling and analysis of residual stress, which has interdependence with the thermal cycle, mechanical response, and residual stress in the process during printing. This review also explores some methods for measuring and minimizing the residual stress during and after the printing process. Residual stress and distortion associated with many input and process parameters that are in complement to thermal cycles in the process are discussed. This review study concludes that the thermal dependency of material characterization and process integration for WAAM to produce structurally sound and defect-free parts remain central issues for future research.
... However, during the deposition process, the previous layers can undergo multiple heating and cooling, and even remelting [3]. The complex thermal cycling process leads to an inhomogeneous structure and performance of the formed parts [4,5], as well as the generation of defects [6,7], which may greatly degrade the quality of the parts. Therefore, it is essential to explore the thermal behavior of the deposited layers based on the long-term development of wire arc additive manufacturing technology. ...
The heat transfer behavior during wire arc additive manufacturing is closely related to the dimensional accuracy and performance of the formed part. To investigate the thermal behavior of stainless steel 316L straight wall part fabricated by the wire arc additive manufacturing process, a three-dimensional transient finite element model is established based on the double elliptic heat source model. At the same time, the temperature measurement experiment on the characteristic position of the substrate is carried out. The thermal cycle curve obtained by the finite element model is in good agreement with the measured result. By analyzing the simulation results, the finite element model established can effectively reveal the thermal behaviors such as melting, solidification, heat accumulation and remelting during the forming process of the straight wall part. In addition, the solidification parameters obtained by the model are correlated with the microstructure. High G/R induces the production of cellular crystals and columnar dendrites, on the contrary, the formation of equiaxial crystals, which provide guidance for the prediction of the morphology of the microstructure.
The tensile and fatigue crack growth rate (FCGR) behavior of SS316L wire deposited on SS316 substrate using wire arc additive manufacturing (WAAM) was studied to assess its potential for fabrication and repair applications. Five initial notch locations near the WAAM-substrate interface were considered for FCGR. Cracks in the deposition direction propagated towards the WAAM region. FCGR of cracks in the build direction accelerated in the WAAM region due to its favorable columnar grain orientation. Overall, FCGR behavior near the WAAM-substrate interface is comparable with wrought alloy, suggesting WAAM’s viability for SS316 fabrication and repair, with satisfactory structural integrity observed in tensile and FCGR behavior.
