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Effects of Substrate Preheating Temperatures on the Microstructure, Properties, and Residual Stress of 12CrNi2 Prepared by Laser Cladding Deposition Technique
摘要： The 12CrNi2 alloy steel powder studied in the present paper is mainly used to manufacture camshafts for nuclear power emergency diesel engines. Laser cladding deposition is of great signi?cance for the manufacture of nuclear power emergency diesel camshafts, which has the advantages of reducing material cost and shortening the manufacturing cycle. However, due to the extremely uneven heating of the components during the deposition process, a complex residual stress ?eld occurs, resulting in crack defects and residual deformation of the components. In the present paper, 12CrNi2 bulk specimens were prepared on the Q460E high-strength structural steel substrate at different preheating temperatures by laser cladding deposition technique, and a ?nite element residual stress analysis model was established to investigate the effects of different preheating temperatures on the microstructure, properties, and residual stress of the specimens. The results of the experiments and ?nite element simulations show that with the increase of preheating temperature, the content of martensite/bainite in the deposited layer decreases, and the ferrite content increases. The proper preheating temperature (150 ?C) has good mechanical properties. The residual stress on the surface of each specimen decreases with the increase of the preheating temperature. The longitudinal stress is greater at the rear-end deposition part, and the lateral residual stress is greater on both sides along the scanning direction.
关键词： substrate preheating,12CrNi2 alloy steel powder,residual stress,laser cladding deposition,microstructure and properties
更新于2025-11-28 14:24:20
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Effects of phase transition temperature and preheating on residual stress in multi-pass & multi-layer laser metal deposition
摘要： To investigate the influences of phase transition temperature and preheating on the residual stress of multi-layer and multi-pass laser metal deposition (LMD), the multi-layer and multi-pass LMD, with and without preheating, were performed using five kinds of alloy with different phase transition features, and their residual stresses were measured using the hole drilling method. A finite-element (FE) model incorporating the phase transition was developed based on experimentally obtained physical property data. The results demonstrated that the low-temperature solid phase transition has a tensile stress relaxation effect, which leads to the formation of a compressive stress area. This relaxation effect was observed to decrease with the increase of the phase transition temperature. The high-temperature solid phase transition has no significant tensile stress relaxation effect during the multi-layer and multi-pass LMD process, which is different from the single track LMD. when the solid phase transition temperature is low, the preheating can improve the uniformity of the stress field only to a certain extent. However, when the preheating increases the lowest temperature of the thermal cycle and makes it higher than the starting point temperature of the solid phase transition, the tensile stress relaxation effect of the solid phase transition can be brought into full play.
关键词： Finite element analysis,Preheating,phase transition temperature,Residual stress,Laser metal deposition
更新于2025-11-28 14:24:20
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Eliminating the crack of laser 3D printed functionally graded material from TA15 to Inconel718 by base preheating
摘要： High quality manufacturing the functionally graded material (FGM) from TA15 to Inconel718 (IN718) has wide application prospects in the aerospace field. However, the crack always can be found in linear gradient structure of the FGM manufactured by laser 3D printing. In the present study, the crack-free FGM was fabricated by laser 3D printing via base preheating. The microstructure and mechanical properties were analyzed in detail to evaluate the mechanism that the preheating process prevented the formation of the crack. The microstructure of the unpreheated FGM presented that the crack mainly formed in the region between 60% and 80% IN718. Obviously, no cracks formed in the preheated sample because base preheating process made the level of internal stress to be below the yield strength. The tensile strength of the FGM with the preheating was 207 MPa. This is a noticeable improvement compared with that fabricated without the preheating, which could not be measured due to the formation of the crack. These research results indicate that the base preheating process can effectively prevent the formation of the crack during laser 3D printing FGMs from Ti- to Ni-based alloys.
关键词： Laser 3D printing,Functionally graded material,Crack,Microstructure,Preheating
更新于2025-09-23 15:19:57
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Defect-free Laser Powder Bed Fusion of Ti-48Al-2Cr-2Nb with a high temperature inductive preheating system
摘要： In the industrial panorama, Laser Powder Bed Fusion systems enable the near net shaping of metal powders into complex geometries with unique design features. This makes the technology appealing for many industrial applications, which require high performance materials combined with lightweight design, lattice structures and organic forms. However, many of the alloys that would be ideal for the realisation of these functional components are classified as difficult to weld due to their cracking sensitivity. γ-TiAl alloys are currently processed via Electron Beam Melting to produce components for energy generation applications. The Electron Beam Melting process provides crack-free processing thanks to the preheating stages between layers, but lacks geometrical precision. The use of laser powder bed fusion could provide the means for higher precision, and therefore an easier post-processing stage. However, industrial Laser Powder Bed Fusion systems employ resistive heating elements underneath the base plate which do not commonly reach the high temperatures required for the processing of γ-TiAl alloys. Thus, elevated temperature preheating of the build part and control over the cooling rate after the deposition process is concluded are amongst the features which require further investigations. In this work, the design and implementation of a novel inductive high temperature Laser Powder Bed Fusion system to process Ti-48Al-2Cr-2Nb is presented. Specimens were built with preheating at 800 °C and the cooling rate at the end of the build was controlled at 5 °C/min. Crack formation was suppressed and apparent density in excess of 99 % was achieved.
关键词： High Temperature,Preheating,TiAl,Laser Powder Bed Fusion,Energy generation
更新于2025-09-19 17:13:59
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Microstructure and properties of 24CrNiMoY alloy steel prepared by direct laser deposited under different preheating temperatures
摘要： The direct laser deposition (DLD) process, evolution mechanism between preheating temperature and structure are visually described in this graph. Fig. 1(a) displays the DLD process design for preheating the substrate, the main heat transfer method is heat conduction. Fig. 1(b) shows the formation mechanism of the pores in the DLD process, it can be seen that the pores in the sample mainly underwent three processes of formation, floating, and growth. Fig. 1(c) exhibits the evolution mechanism between the bainite structure and preheating temperature of 24CrNiMoY alloy steel, it can be deduced the microstructure of the sample changes from lath bainite (LB) to granular bainite (GB) with the rise of preheating temperature. The proper preheating temperature of 200℃ can effectively eliminate the crack, decrease the pores and significantly improve the structure and properties of the DLD 24CrNiMoY alloy steel.
关键词： Preheating,24CrNiMoY alloy steel,Bainite,Direct Laser Deposited,Mechanical properties
更新于2025-09-19 17:13:59
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Prediction of Preheating Temperatures for S690QL High Strength Steel Using FEM-Simulation for High Power Laser Welding
摘要： This study investigates a method for predicting the effect of preheating temperatures on the resulting hardness for high power laser welding of high strength steel. An FEM model is introduced containing a hardness calculation based on an existing model. Moreover, the hardness values of experimental results have been measured in order to show the performance of the model. The hardness calculation requires the chemical composition and the t8/5-time at the point of measurement. It is claimed that a calibration of the melt pool width and depth at room temperature only is enough to get reasonable results from the FEM-model for higher preheating temperatures. From the experimental result of a single experiment the width of a weld seam and the depth was deducted. In this study experiments have been done at various preheating temperatures in order to show the correlation between the model and the experimental results at various temperatures. The hardness equation provides suitable results in the verification with the measurements. The prediction of preheating temperature can be done with the resulting t8/5-time of the FEM-model. This method can decrease the amount of time and costs within a production according to testing and analyzing a matrix of process parameters. Moreover it is concluded that this methodology might be used for single item production.
关键词： Deep penetration laser welding,FEM-welding simulation,High strength steel,Preheating,Predicting hardness
更新于2025-09-19 17:13:59
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Numerical Study on Thermodynamic Behavior during Selective Laser Melting of 24CrNiMo Alloy Steel
摘要： In this paper, a multi-layer and multi-track ?nite element model of 24CrNiMo alloy steel by selective laser melting (SLM) is established by using the ABAQUS software. The distribution and evolution of temperature ?eld and stress ?eld and the in?uence of process parameters on them are systematically studied. The results show that the peak temperature increases from 2153 C and the residual stress increases from 335 MPa to 364 MPa with increasing laser power from 200 W to 300 W; the peak temperature decreases from 2905 C and the residual stress increases from 327 MPa to 363 MPa with increasing scanning speed from 150 mm/s to 250 mm/s; the peak C and the residual stress decreases from 354 MPa to 300 temperature increases from 2621 MPa with increasing preheating temperature from 25 C. Far away from scanning area, far away from starting point, and the adjacent areas with vertical scanning direction, resulting in a uniform temperature distribution, help to reduce the residual stress. Due to the remelting e?ect, the interlayer scanning angle changing helps to release the residual stress of the former layer causing a smaller residual stress after redistribution.
关键词： substrate preheating,?nite element analysis,thermodynamic behavior,selective laser melting,scanning strategy,24CrNiMo alloy steel
更新于2025-09-16 10:30:52
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Effects of Preheating Temperature at Primary Shear Zone in Laser Assisted Milling Process
摘要： In this paper, preheating temperature was investigated for the laser assisted machining (LAM) of Inconel 718 under different conditions for the milling test. The experimental results show that the requirement of laser power for the particularly preheating temperature proportionally increased with the table speed. The resultant cutting force for sufficient shearing work material in LAM was lower than conventional machining (CM) approximately 11, 21 and 28% for the cutting speed of 30, 50 and 75 m/min, respectively. The tool wear in LAM could be improved at relatively high cutting speed of 75 m/min and the hardness of machined surface in LAM was slightly higher than CM.
关键词： Laser assisted machining,Milling,Inconel 718,Preheating temperature
更新于2025-09-16 10:30:52
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A study on preheating temperature and heat affected depth according to various laser beam angle for laser-assisted machining
摘要： Laser-assisted machining (LAM) is a new method and actively researched for various difficult to machine materials. In LAM, machining is carried after prediction of material removal temperature (preheating temperature) for material with fixed cutting depth using a laser source. Among the various difficult-to-cut materials, Inconel 718, nickel-based super alloys, is difficult to machine due high strength at elevated temperature and low thermal conductivity. Studies on machining of Inconel 718 using a laser has been performed for various position of laser source to reveal the process benefits of Inconel 718 with fixed cutting depth. But there are no studies and results on prediction of heat affected depth for preheating temperature using laser assisted machining of Inconel 718 on various laser beam angle. So, in the present study, the effect of application of laser when applied at different angles is studied by two different methods- one with offset and other without offset. Finite element method is used to perform the simulations. This contribution brings a new novelty to the present research work on metal cutting domain using laser. The heat affected depth was also found and compared with depth obtained through experiments. And, the error percentage found for heat affected depth and preheating temperature is about 11%. The experimental results reveal that laser beam at an angle of 60° has maximum depth of cut, while minimum depth of cut is found at 90°.
关键词： laser beam angle,laser-assisted machining,heat affected depth,preheating temperature
更新于2025-09-16 10:30:52
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Application of base plate preheating during selective laser melting
摘要： Base plate preheating is one of the recent enhancing tools added to the process of Selective Laser Melting (SLM). This tool aims at a reduction of thermal stresses in SLM parts, achieved by decreasing the thermal gradients during SLM processing. In the current study, base plate preheating up to a temperature of 400°C is applied during SLM of 4 different materials, including aluminum 7075 alloy, nickel alloy Hastelloy X, H13 tool steel and CoCr. General trends, as well as material specific effects are discussed regarding part density, crack formation, internal stresses, microstructure and mechanical properties. These show how base plate preheating can induce different influences according to each particular material category.
关键词： Selective Laser Melting (SLM),Base plate preheating
更新于2025-09-12 10:27:22