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Rachid Fakir - One of the best experts on this subject based on the ideXlab platform.
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effects of Laser Hardening process parameters on hardness profile of 4340 steel spline an experimental approach
THE Coatings, 2020Co-Authors: Noureddine Barka, Sasan Sattarpanah Karganroudi, Rachid Fakir, Patrick Thibeault, Vincent Blériot Feujofack KemdaAbstract:This study displays the effect of Laser surface Hardening parameters on the hardness profile (case depth) of a splined shaft made of AISI 4340 steel. The approach is mainly based on experimental tests wherein the hardness profile of Laser hardened splines is acquired using micro-hardness measurements. These results are then evaluated with statistical analysis (ANOVA) to determine the principal effect and the contributions of each parameter in the Laser Hardening process. Using empirical correlations, the case depth of splined shaft at tip and root of spline’s teeth is also estimated and verified with measured data. The obtained results were then used to study the sensitivity of the measured case depths according to the evolution of Laser process parameters and geometrical factors. The feasibility and efficiency of the proposed approach lead to a reliable statistical model in which the hardness profile of the spline is estimated with respect to its specific geometry.
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trempe au Laser analyse numerique et experimentale de l effet du durcissement au Laser sur les proprietes mecaniques en statique et en fatigue de l acier aisi 4340
2019Co-Authors: Rachid FakirAbstract:RESUME: Le durcissement au Laser en surface est de plus en plus utilise par l'industrie du transport civil et militaire pour l'amelioration de la durete, la resistance a l'usure, la resistance mecanique en statique et en fatigue des composantes structurelles tout en conservant indemnes les proprietes de la masse telle que la tenacite et la ductilite. La maitrise de ce procede necessite une connaissance precise des facteurs physiques qui influencent la reponse du procede telles que le type du materiau, le fini de surface, le coefficient d'absorption, la puissance Laser, l'angle d'incidence du faisceau Laser et la vitesse de deplacement de la tache focale. En ayant pour but le developpement des techniques de prediction de la profondeur durcie, et des proprietes mecaniques en statique et en fatigue d'un cylindre en acier AISI 4340 en haute vitesse de rotation, cette recherche repond a six objectifs particuliers : 1/ Analyse des proprietes mecaniques de l'acier AISI 4340 traite thermiquement dans la masse en utilisant un four de laboratoire et refroidi dans trois fluides differents. 2/ Analyse numerique par la methode des differences finies (MDF) et validation experimentale, du durcissement au Laser en un point stationnaire (sans vitesse de balayage) d'un cylindre d'acier AISI 4340 en rotation. 3/ Investigation numerique MDF du durcissement au Laser d'une eprouvette cylindrique en acier AISI 4340, en introduisant le deplacement du faisceau Laser au niveau des conditions aux limites. 4/ Analyse numerique par la methode des elements finis (MEF) et validation experimentale, de la variation du profil de durete dans le cas d'une trempe au Laser (puissance constante) appliquee a des eprouvettes cylindriques en acier AISI 4340. 5/ Optimisation de la profondeur durcie d'un cylindre en acier AISI 4340 par la methode des elements finis (FEM) et des tests experimentaux, au moyen d'un controle actif des parametres Laser. 6/ Analyse du comportement mecanique en statique et en fatigue d'eprouvettes cylindriques normalisees (ASTM E8) en acier AISI 4340 durcies au Laser. L'approche d'analyse de la distribution de la temperature a ete developpee sous le logiciel MATLAB pour une discretisation des equations differentielles en differences finies, a ete validee par le logiciel COMOSL et par des tests experimentaux en laboratoire. L'approche d'analyse de la variation des proprietes mecaniques en statique et en fatigue, en fonction des parametres de durcissement au Laser est fondee sur un plan d'experience DOE et une analyse de variance correlee avec la puissance de prediction des reseaux de neurones. L'approche proposee a permis, de mettre en evidence les variations du coefficient d'absorption en fonction des conditions d'operation, d'analyser la dynamique des echanges thermiques au moyen des nombres adimensionnels, de confirmer la robustesse de la prediction numerique du profil de temperature versus la profondeur durcie, et finalement de proposer un modele robuste de prediction des proprietes mecaniques en statique et en fatigue avec un ecart relatif de moins de 10%. Finalement, nous montrons qu'il est possible d'uniformiser le profil de durete par un asservissement des parametres de durcissement au Laser. Et que la trempe autogene peut ameliorer de 20 a 40% la limite d'endurance en fatigue pour des specimens de diametre de 9 a 10 mm. -- Mot(s) cle(s) en francais : Trempe au Laser, bilan des echanges thermiques, modelisation numerique, differences finies et elements finis, analyse de variance, reseaux de neurones, proprietes mecaniques, resistance en fatigue, AISI 4340. -- ABSTRACT: The surface Laser Hardening is increasingly used by the civilian and military transportation industry for improving hardness, wear resistance, the mechanical resistance in static and fatigue of the structural components while keeping intact the properties of the mass such as toughness and ductility. The control of this process requires a precise knowledge of physical factors, that influence the response of the process like the type of material, the surface finish, the absorption coefficient, the Laser power, the angle of incidence of the Laser beam and the speed of displacement of the focal spot. With the aim of developing hardened depth prediction techniques, and mechanical properties in static and fatigue of steel AISI 4340, this research meets six specific objectives: 1/ Analysis of the mechanical properties of AISI 4340 steel heat-treated in the mass, using a laboratory oven, and cooled in three different fluids. 2/ Numerical analysis by the finite difference method (FDM) and experimental analysis of Laser Hardening process at a stationary point (without scanning speed) of a cylinder of steel AISI 4340 in rotation. 3/ FDM numerical investigation of the Laser Hardening process, of a cylinder in steel AISI 4340, by introducing the displacement parameter of the Laser source at the boundary conditions. 4/ Numerical analysis by the finite element method (FEM) and experimental validation of the variation of the hardness profile in the case of Laser Hardening (constant power) applied to cylindrical specimens of steel AISI 4340. 5/ Optimization of the case depth of a steel cylinder AISI 4340 by the finite element method (FEM) and experimental tests by means of an active control of the Laser parameters. 6/ Analysis of mechanical behavior in static and fatigue of standard cylindrical specimens (ASTM E8) in AISI 4340 steel heat-treated by Laser. The analysis approach of the temperature distribution has been developed in the MATLAB software for a discretization of differential equations in finite difference method, and has been validated by the COMSOL software and by experimental tests in the laboratory. The analysis approach of the variation of mechanical properties in static and fatigue, according to the Laser Hardening parameters is based on a DOE experience plan and an analysis of variance correlated with the predictive power of neural networks. The proposed approach allowed to highlight the variations of the absorption coefficient according to the operating conditions, to analyze the dynamics of thermal exchanges by means of adimensional numbers, to confirm the robustness of the numerical prediction of the temperature profile versus the case depth, and finally to propose a robust model for predicting mechanical properties in static and fatigue with a relative difference of less than 10%. Finally, we show that it is possible to regularize the hardness profile by a servo control of the Laser Hardening parameters. And that autogenous Laser quenching can improve the fatigue endurance limit by up to 20-40% for specimens with a diameter of 9 to 10 mm. -- Mot(s) cle(s) en anglais : Laser Hardening, balance of thermal exchanges, numerical modeling, finite difference method and finite element method, analysis of variance, neural networks, mechanical properties, fatigue resistance, AISI 4340.
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Case study of Laser Hardening process applied to 4340 steel cylindrical specimens using simulation and experimental validation
Case Studies in Thermal Engineering, 2018Co-Authors: Rachid Fakir, Noureddine Barka, Jean BrousseauAbstract:This paper presents a numerical approach that can predict the temperature profile of cylindrical specimens made with AISI 4340 steel according to Laser Hardening process parameters. The developed model was built using the finite difference method (FDM) and validated using commercial finite element tools and experimental data. The proposed approach was constructed progressively by (i) examination of the temperature distribution using heat diffusion equations, boundary conditions and material properties (ii), discretization of the mathematical model using the finite difference method, (iii) validation of the proposed approach using experimental tests and simulation with COMSOL Multiphysics software and (iv) analysis and discussion of the results. The feasibility and effectiveness of the proposed approach led to an accurate, reliable model capable of predicting the temperature profile inside the heated component.
Yung C. Shin - One of the best experts on this subject based on the ideXlab platform.
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predictive modeling and experimental results for residual stresses in Laser Hardening of aisi 4140 steel by a high power diode Laser
Surface & Coatings Technology, 2009Co-Authors: Neil S Bailey, Wenda Tan, Yung C. ShinAbstract:A predictive model for residual stresses induced in a Laser hardened workpiece of AISI 4140 steel with no melting has been developed and experimentally verified. A transient three-dimensional thermal and kinetic model is first solved to obtain the temperature and solid phase history of the workpiece, which is then sequentially coupled to a three-dimensional stress model to predict residual stresses. The phase transformation strains are added to the thermal strains at each time step during the heating and cooling cycles to obtain the resultant residual stresses in the workpiece. The importance of considering phase transformation has been explained through the comparison of the magnitudes of residual stresses with and without the inclusion of phase transformation kinetics. The model predicted strong compressive residual stresses of about 200 MPa in the heat affected zone due to austenite-to-martensite transformation. The predictions matched well with the X-ray diffraction measurements.
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predictive modeling of multi track Laser Hardening of aisi 4140 steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: Ritesh S Lakhkar, Yung C. Shin, Matthew John M. KraneAbstract:Abstract Laser Hardening provides benefits over the conventional Hardening processes, including minimum distortion in the parts and the absence of a quenchant. This process is also faster than conventional Hardening processes and can be used for selective Hardening of specific areas of components. One known problem with Laser Hardening in steels, however, is back tempering when a large area is hardened by multiple, overlapping passes. This study focused on the development of a numerical model to predict the back tempering in multi-track Laser Hardening. A tempering model was combined with existing models of thermal behavior and phase change kinetics, which were developed earlier in the authors’ group, to predict three-dimensional hardness profiles after multiple track Laser Hardening. The combined model was first validated through multi-track Laser Hardening tests and then used to predict and optimize the Laser hardened case depth in multi-track Laser Hardening of AISI 4140 steel. The predictions and parameters optimized to obtain maximum case depth with the least variation along width of the hardened zone were experimentally verified. Case depths up to 2 mm were obtained with 5 mm overlapping of Laser tracks.
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Predictive modeling of Laser Hardening of AISI5150H steels
International Journal of Machine Tools & Manufacture, 2007Co-Authors: Rahul Patwa, Yung C. ShinAbstract:Abstract This paper presents accurate predictive modeling of the Laser Hardening process in terms of Laser operating parameters and initial microstructure without the need of any experimental data. The model provides the diagrams that are useful for predicting hardness profiles, optimizing practical process parameters and assessing the potential of Laser Hardening for different steels. It is shown that the hardness and depth of the hardened layer in hypoeutectoid steels (carbon wt% The model combines a three-dimensional transient numerical solution for a rotating cylinder undergoing Laser heating by a translating Laser beam with a kinetic model describing pearlite dissolution, carbon redistribution in austenite and subsequent transformation to martensite by utilizing the feedback from the CCT diagram. In order to validate the thermal model and assert the accuracy of temperature predictions the temperature was measured using an infrared camera and a good agreement between the predicted and measured temperatures is shown. Results are presented as processing maps, which show how the case depth and hardness depend on input operating parameters. The good agreement between the measured and predicted hardness profiles ascertains the accuracy of the thermal-kinetic model developed for AISI5150H steels.
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Predictive modeling and experimental results for Laser Hardening of AISI 1536 steel with complex geometric features by a high power diode Laser
Surface and Coatings Technology, 2006Co-Authors: Stephen Skvarenina, Yung C. ShinAbstract:This paper presents predictive modeling and experimental results on Laser Hardening of AISI 1536 steel shafts with a complex geometric feature. A three-dimensional thermal model is used to predict the workpiece temperature distribution, which is coupled to a two-dimensional kinetic model to predict the resultant hardness and phase distribution. Surface temperature measurements are performed to validate the thermal model, while the kinetic model is validated through furnace Hardening and Laser Hardening experiments. A 2.5-mm case depth is achieved on simple geometry parts, while a 1.5-mm case depth is obtained on parts with a groove of 2.0-mm radius. The case hardness values and distributions show good agreement with predicted results and are found to be uniform throughout, with the values between 55 and 57 in Rockwell C.
Alessandro Fortunato - One of the best experts on this subject based on the ideXlab platform.
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a comprehensive model for Laser Hardening of carbon steels
Journal of Manufacturing Science and Engineering-transactions of The Asme, 2013Co-Authors: Alessandro Fortunato, Leonardo Orazi, Alessandro Ascari, Erica Liverani, Gabriele CuccoliniAbstract:This article illustrates the development of a complete and exhaustive mathematical model for the simulation of Laser transformation Hardening of hypo-eutectoid carbon steels. The authors propose an integrated approach aimed at taking into consideration all the the phenomena involved in this manufacturing process, with particular attention to implementing easy mathematical models in order to optimize the trade-off between the accuracy of the predicted results and the computational times. The proposed models involve the calculation of the 3D thermal field occurring into the workpiece and predict the microstructural evolution of the target material exploiting an original approach based on the definition of thermodynamic thresholds which can be considered as a physical constant of the material itself. Several parameters and phenomena are taken into consideration in order to accurately simulate the process: Laser beam characteristics, fast austenization of the steel and tempering effect due to mutually interacting beam trajectories.Copyright © 2013 by ASME
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numerical evaluation of the reflectivity coefficient in Laser surface Hardening simulation
Surface & Coatings Technology, 2012Co-Authors: Alessandro Fortunato, Leonardo Orazi, Giampaolo Campana, Alessandro Ascari, Gabriele CuccoliniAbstract:Abstract This paper reports the results concerning the simulation of a Laser surface Hardening process of a cylindrical surface. In particular it focuses on the problems related to the definition of the physical parameter values necessary in order to achieve an accurate and reliable simulation. The strict dependency of Laser process simulation results on the physical parameters describing the target material is, in fact, a well known matter, especially considering that the values of these parameters change during the process dependently on temperature and time. Moreover in Laser surface Hardening this problem is even more important because melting of the target material should be avoided, surface roughness plays an important role and, sometimes, the surface is coated with absorbent layers. These factors increase the complexity of the simulations and make the evaluation of the physical parameters more difficult and critical. The results presented in this paper are obtained on AISI420B steel, coated with graphite and treated with a direct diode Laser. Considering the above mentioned conditions, a plausible temperature dependent reflectivity coefficient was evaluated and its robustness was investigated. This reflectivity coefficient can be used with a good approximation for the simulation of Laser Hardening treatments of many carbon steels.
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an efficient model for Laser surface Hardening of hypo eutectoid steels
Applied Surface Science, 2010Co-Authors: Leonardo Orazi, Alessandro Fortunato, Gabriele Cuccolini, Giovanni TaniAbstract:Abstract This paper presents a model able to predict the austenization of hypo-eutectoid steels during very fast heat cycle such as Laser Hardening. Laser surface Hardening is a process highly suitable for hypo-eutectoid carbon steels with carbon content below 0.6% or for low alloy steels where the critical cooling rate is reached by means of the thermal inertia of the bulk. As proposed by many authors, the severe heat cycle occurring in Laser Hardening leads to the pearlite to austenite microstructures transformation happening to a temperature much higher than the eutectoid temperature A c 1 and, afterwards, all the austenite predicted during the heating phase become martensite during quenching. Anyway, all these models usually generate a predicted hardness profile into the material depth with an on–off behavior or very complicated and time consumed software simulators. In this paper, a new austenization model for fast heating processes based on the austenite transformation time parameter I p → a is proposed. By means of the I p → a parameter it is possible to predict the typical hardness transition from the treated surface to the base material. At the same time, this new austenization model also reduces the calculation time. I p → a was determined by experimental tests and it was postulated to be constant for low-medium carbon steels. Several experimental examples are proposed to validate the assumptions and to show the accuracy of the model.
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Laser Hardening of 3D complex parts: industrial applications and simulation results
AITeM, 2009Co-Authors: Giovanni Tani, Alessandro Fortunato, Giampaolo Campana, Orazi Leonardo, A. Ascari, Cuccolini GabrieleAbstract:Laser surface Hardening of mechanical steel components is a rapidly developing manufacturing technology which allows to deal with small, confined and complex surfaces. It allows, in fact, to accurately focus the Hardening treatment only where it is needed, without affecting the surrounding base material. This prerogative differentiates Laser Hardening from any other surface treatment, such as flame or induction, and makes possible to save time and energy during the process. On the other hand, when large surfaces have to be treated, the relatively small Laser spot makes necessary to optimize new process strategies aimed at dealing with the inevitable tempering effect occurring when overlapping Laser beam trajectories take place.According to these considerations the article analyzes the possibility to deal with large cylindrical surfaces, by means of Laser surface Hardening, exploiting the "apparent spot" technique. This solution applies on axisymmetric components and implies the combination of a rotation of the part to be treated and of the linear motion of the Laser beam. In order to study the optimal process parameters involved in this technique a simulation analysis was carried out by means of a proprietary simulation software developed by the research group and a subsequent experimental campaign made possible to validate the whole procedure
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Prediction of hypo eutectoid steel softening due to tempering phenomena in Laser surface Hardening
CIRP Annals, 2008Co-Authors: Giovanni Tani, Leonardo Orazi, Alessandro FortunatoAbstract:Abstract The paper presents a mathematical model for predicting material mechanical property variation, in Laser Hardening of hypo eutectoid steel, when the softening effects due to the overlapping trajectories are considered. This generally occurs during Laser Hardening of industrial parts, especially when wide areas have to be treated, due to the tempering phenomena. An original tempering model for the prediction of the hardness reduction is presented in this paper. The proposed model is integrated in a Laser Hardening simulation package, previously developed by the authors. Experimental activities are also presented to validate the model.
Gabriele Cuccolini - One of the best experts on this subject based on the ideXlab platform.
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a comprehensive model for Laser Hardening of carbon steels
Journal of Manufacturing Science and Engineering-transactions of The Asme, 2013Co-Authors: Alessandro Fortunato, Leonardo Orazi, Alessandro Ascari, Erica Liverani, Gabriele CuccoliniAbstract:This article illustrates the development of a complete and exhaustive mathematical model for the simulation of Laser transformation Hardening of hypo-eutectoid carbon steels. The authors propose an integrated approach aimed at taking into consideration all the the phenomena involved in this manufacturing process, with particular attention to implementing easy mathematical models in order to optimize the trade-off between the accuracy of the predicted results and the computational times. The proposed models involve the calculation of the 3D thermal field occurring into the workpiece and predict the microstructural evolution of the target material exploiting an original approach based on the definition of thermodynamic thresholds which can be considered as a physical constant of the material itself. Several parameters and phenomena are taken into consideration in order to accurately simulate the process: Laser beam characteristics, fast austenization of the steel and tempering effect due to mutually interacting beam trajectories.Copyright © 2013 by ASME
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numerical evaluation of the reflectivity coefficient in Laser surface Hardening simulation
Surface & Coatings Technology, 2012Co-Authors: Alessandro Fortunato, Leonardo Orazi, Giampaolo Campana, Alessandro Ascari, Gabriele CuccoliniAbstract:Abstract This paper reports the results concerning the simulation of a Laser surface Hardening process of a cylindrical surface. In particular it focuses on the problems related to the definition of the physical parameter values necessary in order to achieve an accurate and reliable simulation. The strict dependency of Laser process simulation results on the physical parameters describing the target material is, in fact, a well known matter, especially considering that the values of these parameters change during the process dependently on temperature and time. Moreover in Laser surface Hardening this problem is even more important because melting of the target material should be avoided, surface roughness plays an important role and, sometimes, the surface is coated with absorbent layers. These factors increase the complexity of the simulations and make the evaluation of the physical parameters more difficult and critical. The results presented in this paper are obtained on AISI420B steel, coated with graphite and treated with a direct diode Laser. Considering the above mentioned conditions, a plausible temperature dependent reflectivity coefficient was evaluated and its robustness was investigated. This reflectivity coefficient can be used with a good approximation for the simulation of Laser Hardening treatments of many carbon steels.
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an efficient model for Laser surface Hardening of hypo eutectoid steels
Applied Surface Science, 2010Co-Authors: Leonardo Orazi, Alessandro Fortunato, Gabriele Cuccolini, Giovanni TaniAbstract:Abstract This paper presents a model able to predict the austenization of hypo-eutectoid steels during very fast heat cycle such as Laser Hardening. Laser surface Hardening is a process highly suitable for hypo-eutectoid carbon steels with carbon content below 0.6% or for low alloy steels where the critical cooling rate is reached by means of the thermal inertia of the bulk. As proposed by many authors, the severe heat cycle occurring in Laser Hardening leads to the pearlite to austenite microstructures transformation happening to a temperature much higher than the eutectoid temperature A c 1 and, afterwards, all the austenite predicted during the heating phase become martensite during quenching. Anyway, all these models usually generate a predicted hardness profile into the material depth with an on–off behavior or very complicated and time consumed software simulators. In this paper, a new austenization model for fast heating processes based on the austenite transformation time parameter I p → a is proposed. By means of the I p → a parameter it is possible to predict the typical hardness transition from the treated surface to the base material. At the same time, this new austenization model also reduces the calculation time. I p → a was determined by experimental tests and it was postulated to be constant for low-medium carbon steels. Several experimental examples are proposed to validate the assumptions and to show the accuracy of the model.
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Laser Hardening process simulation for mechanical parts
Proceedings of SPIE, 2007Co-Authors: Giovanni Tani, Leonardo Orazi, Alessandro Fortunato, Giampaolo Campana, Gabriele CuccoliniAbstract:ABSTRACT In this paper a numerical simulation of Laser Hardening process is presented. The Finite Dierence Method(FDM) was used to solve the heat transfer and the carbon diu sion equations for a dened workpiece geometry.The model is able to predict the thermal cycle into the target material, the phase transformations and theresultingmicro-structuresaccordingtothe Laserparameters,the workpiecedimensions andthe physicalpropertiesof the workpiece. The eects of the overlapping tracks of the Laser beam on the resulting micro-structures is alsoconsidered.The initial workpiece micro-structure is taken into acco unt in the simulation by a digitized photomicrographof the ferrite perlite distribution before the thermal cycle.Experimental tests were realized on a C43 plate and the good agreement between the theoretical and exper-imental results is shown.Keywords: Laser Hardening, numerical simulation, process planning. 1. INTRODUCTION LaserHardeningofsteel componentsis a stable processwhere veryhard, wearresistancesurfacescan be uniformlyobtained into the workpiece when the correct process pa rameters are set. It allows to treat complex shapes,usually very diculty to realize with conventional surface Hardening, with less distortions than that caused byame or induction Hardening.This process is becoming widely used in industrial environment due to the development of new generationLaser sources. Diode Laser with high power density, high eciency and very uniform distribution are commonlyavailable together with the last generation of high power ber Lasers. These new types of sources usually havevery compact resonators like the diode ones, or the Laser beam can be easily delivered to the workpieces bymeans of optic bers, like the ber or the Nd:Yag Lasers. For these reasons, surface heat treatment, usually anoutsourcing operation for the small-medium mechanical company, always more often is realized from the samecompany which realize the cutting operations. Many eorts are nowadays conducted to integrate in a machinecenter for metal cutting the operations of surface Hardening considering the Laser beam as a conventional tool.The economic aspect is crucial for the development of the Laser technology in Industry. For the completeexploitation of the Laser resources, in fact, it is fundamental to consider the technological advantages of theLaser together with the high capital costs of the systems: widespread use of Lasers in industry for heat treatingmainly depends on the cost of the treated component. In general, Laser Hardening can be more economicallyapplied respect to the conventional processes when batches of small dimensions or when complex shapes mustbe hardened. In this direction, the challenge is to increase the exibility of the Laser technology.Laser Hardening is a quite complex process which involves many parameters: the Laser parameters like the power density and distribution, the spot dimension and the Laser beam velocitywhich determine the heat cycle in the workpiece;
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Optimization Strategies of Laser Hardening of Hypo-eutectoid Steel
Manufacturing Systems and Technologies for the New Frontier, 2024Co-Authors: Giovanni Tani, Leonardo Orazi, Alessandro Fortunato, Giampaolo Campana, Alessandro Ascari, Gabriele CuccoliniAbstract:The interest towards Laser Hardening of steels has been increasing since the last few years due to its undoubted advantages. The main drawback affecting this manufacturing technology is the tempering effect induced when multiple passes on the same surface must be carried out. In order to minimize the softening effect due to tempering and to speed up the process a numerical model for the simulation of the treatment is proposed. This model is able to detect the optimal Laser path trajectory according to the source parameters and the scanning velocity, and it is able to predict the resulting microstructures and the relating hardness. Some examples on an hypo-eutectoid steel are presented together with validation tests.
Giovanni Tani - One of the best experts on this subject based on the ideXlab platform.
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an efficient model for Laser surface Hardening of hypo eutectoid steels
Applied Surface Science, 2010Co-Authors: Leonardo Orazi, Alessandro Fortunato, Gabriele Cuccolini, Giovanni TaniAbstract:Abstract This paper presents a model able to predict the austenization of hypo-eutectoid steels during very fast heat cycle such as Laser Hardening. Laser surface Hardening is a process highly suitable for hypo-eutectoid carbon steels with carbon content below 0.6% or for low alloy steels where the critical cooling rate is reached by means of the thermal inertia of the bulk. As proposed by many authors, the severe heat cycle occurring in Laser Hardening leads to the pearlite to austenite microstructures transformation happening to a temperature much higher than the eutectoid temperature A c 1 and, afterwards, all the austenite predicted during the heating phase become martensite during quenching. Anyway, all these models usually generate a predicted hardness profile into the material depth with an on–off behavior or very complicated and time consumed software simulators. In this paper, a new austenization model for fast heating processes based on the austenite transformation time parameter I p → a is proposed. By means of the I p → a parameter it is possible to predict the typical hardness transition from the treated surface to the base material. At the same time, this new austenization model also reduces the calculation time. I p → a was determined by experimental tests and it was postulated to be constant for low-medium carbon steels. Several experimental examples are proposed to validate the assumptions and to show the accuracy of the model.
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Laser Hardening of 3D complex parts: industrial applications and simulation results
AITeM, 2009Co-Authors: Giovanni Tani, Alessandro Fortunato, Giampaolo Campana, Orazi Leonardo, A. Ascari, Cuccolini GabrieleAbstract:Laser surface Hardening of mechanical steel components is a rapidly developing manufacturing technology which allows to deal with small, confined and complex surfaces. It allows, in fact, to accurately focus the Hardening treatment only where it is needed, without affecting the surrounding base material. This prerogative differentiates Laser Hardening from any other surface treatment, such as flame or induction, and makes possible to save time and energy during the process. On the other hand, when large surfaces have to be treated, the relatively small Laser spot makes necessary to optimize new process strategies aimed at dealing with the inevitable tempering effect occurring when overlapping Laser beam trajectories take place.According to these considerations the article analyzes the possibility to deal with large cylindrical surfaces, by means of Laser surface Hardening, exploiting the "apparent spot" technique. This solution applies on axisymmetric components and implies the combination of a rotation of the part to be treated and of the linear motion of the Laser beam. In order to study the optimal process parameters involved in this technique a simulation analysis was carried out by means of a proprietary simulation software developed by the research group and a subsequent experimental campaign made possible to validate the whole procedure
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Prediction of hypo eutectoid steel softening due to tempering phenomena in Laser surface Hardening
CIRP Annals, 2008Co-Authors: Giovanni Tani, Leonardo Orazi, Alessandro FortunatoAbstract:Abstract The paper presents a mathematical model for predicting material mechanical property variation, in Laser Hardening of hypo eutectoid steel, when the softening effects due to the overlapping trajectories are considered. This generally occurs during Laser Hardening of industrial parts, especially when wide areas have to be treated, due to the tempering phenomena. An original tempering model for the prediction of the hardness reduction is presented in this paper. The proposed model is integrated in a Laser Hardening simulation package, previously developed by the authors. Experimental activities are also presented to validate the model.
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Laser Hardening process simulation for mechanical parts
Proceedings of SPIE, 2007Co-Authors: Giovanni Tani, Leonardo Orazi, Alessandro Fortunato, Giampaolo Campana, Gabriele CuccoliniAbstract:ABSTRACT In this paper a numerical simulation of Laser Hardening process is presented. The Finite Dierence Method(FDM) was used to solve the heat transfer and the carbon diu sion equations for a dened workpiece geometry.The model is able to predict the thermal cycle into the target material, the phase transformations and theresultingmicro-structuresaccordingtothe Laserparameters,the workpiecedimensions andthe physicalpropertiesof the workpiece. The eects of the overlapping tracks of the Laser beam on the resulting micro-structures is alsoconsidered.The initial workpiece micro-structure is taken into acco unt in the simulation by a digitized photomicrographof the ferrite perlite distribution before the thermal cycle.Experimental tests were realized on a C43 plate and the good agreement between the theoretical and exper-imental results is shown.Keywords: Laser Hardening, numerical simulation, process planning. 1. INTRODUCTION LaserHardeningofsteel componentsis a stable processwhere veryhard, wearresistancesurfacescan be uniformlyobtained into the workpiece when the correct process pa rameters are set. It allows to treat complex shapes,usually very diculty to realize with conventional surface Hardening, with less distortions than that caused byame or induction Hardening.This process is becoming widely used in industrial environment due to the development of new generationLaser sources. Diode Laser with high power density, high eciency and very uniform distribution are commonlyavailable together with the last generation of high power ber Lasers. These new types of sources usually havevery compact resonators like the diode ones, or the Laser beam can be easily delivered to the workpieces bymeans of optic bers, like the ber or the Nd:Yag Lasers. For these reasons, surface heat treatment, usually anoutsourcing operation for the small-medium mechanical company, always more often is realized from the samecompany which realize the cutting operations. Many eorts are nowadays conducted to integrate in a machinecenter for metal cutting the operations of surface Hardening considering the Laser beam as a conventional tool.The economic aspect is crucial for the development of the Laser technology in Industry. For the completeexploitation of the Laser resources, in fact, it is fundamental to consider the technological advantages of theLaser together with the high capital costs of the systems: widespread use of Lasers in industry for heat treatingmainly depends on the cost of the treated component. In general, Laser Hardening can be more economicallyapplied respect to the conventional processes when batches of small dimensions or when complex shapes mustbe hardened. In this direction, the challenge is to increase the exibility of the Laser technology.Laser Hardening is a quite complex process which involves many parameters: the Laser parameters like the power density and distribution, the spot dimension and the Laser beam velocitywhich determine the heat cycle in the workpiece;
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Optimization Strategies of Laser Hardening of Hypo-eutectoid Steel
Manufacturing Systems and Technologies for the New Frontier, 2024Co-Authors: Giovanni Tani, Leonardo Orazi, Alessandro Fortunato, Giampaolo Campana, Alessandro Ascari, Gabriele CuccoliniAbstract:The interest towards Laser Hardening of steels has been increasing since the last few years due to its undoubted advantages. The main drawback affecting this manufacturing technology is the tempering effect induced when multiple passes on the same surface must be carried out. In order to minimize the softening effect due to tempering and to speed up the process a numerical model for the simulation of the treatment is proposed. This model is able to detect the optimal Laser path trajectory according to the source parameters and the scanning velocity, and it is able to predict the resulting microstructures and the relating hardness. Some examples on an hypo-eutectoid steel are presented together with validation tests.
