Mathematical modeling and experimental analysis of the hardened zone in laser treatment of a 1045 AISI steel (original) (raw)
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A semi-empirical method for predicting hardened case depths in laser heat treating
1988
Some predictions on the hardness and hardening depths on laser heat treatment of steels can be obtained when specific characteristicsof both laser processes (heating and cooling rates) and laser heat treated steels (microhardness profiles) are taken into account. Some controlled surface temperature laser heat treatments have been carried out with a medium power C.W. CO laser on a medium carbon steel (AISI/SAE1045), allowing these prgdictions to be tested. In particular, knowing the surfacetemperaturehas enabled an analytical algorithm to be used to describe thermal processes and a simple exponential expression to be employed to carefully predict the hardened case depth.
Journal of Applied Mathematics and Physics
This paper presents a numerical and experimental analysis study of the temperature distribution in a cylindrical specimen heat treated by laser and quenched in ambient temperature. The cylinder studied is made of AISI-4340 steel and has a diameter of 14.5-mm and a length of 50-mm. The temperature distribution is discretized by using a three-dimensional numerical finite difference method. The temperature gradient of the transformation of the microstructure is generated by a laser source Nd-YAG 3.0-kW manipulated using a robotic arm programmed to control the movements of the laser source in space and in time. The experimental measurement of surface temperature and air temperature in the vicinity of the specimen allows us to determine the values of the absorption coefficient and the coefficient of heat transfer by convection, which are essential data for a precise numerical prediction of the case depth. Despite an unsteady dynamic regime at the level of convective and radiation heat losses, the analysis of the averaged results of the temperature sensors shows a consistency with the results of microhardness measurements. The feasibility and effectiveness of the proposed approach lead to an accurate and reliable mathematical model able to predict the temperature distribution in a cylindrical workpiece heat treated by laser.
Laser Surface Hardening of Tool Steels—Experimental and Numerical Analysis
Journal of Surface Engineered Materials and Advanced Technology, 2013
This research work is focused on both experimental and numerical analysis of laser surface hardening of AISI M2 high speed tool steel. Experimental analysis aims at clarifying effect of different laser processing parameters on properties and performance of laser surface treated specimens. Numerical analysis is concerned with analytical approaches that provide efficient tools for estimation of surface temperature, surface hardness and hardened depth as a function of laser surface hardening parameters. Results indicated that optimization of laser processing parameters including laser power, laser spot size and processing speed combination is of considerable importance for achieving maximum surface hardness and deepest hardened zone. In this concern, higher laser power, larger spot size and lower processing speed are more efficient. Hardened zone with 1.25 mm depth and 996 HV surface hardness was obtained using 1800 W laser power, 4 mm laser spot size and 0.5 m/min laser processing speed. The obtained maximum hardness of laser surface treated specimen is 23% higher than that of conventionally heat treated specimen. This in turn has resulted in 30% increase in wear resistance of laser surface treated specimen. Numerical analysis has been carried out for calculation of temperature gradient and cooling rate based on Ashby and Easterling equations. Then, surface hardness and hardened depth have been numerically estimated based on available Design-Expert software. Numerical results indicated that cooling rate of laser surface treated specimen is high enough to be beyond the nose of the CCT diagram of the used steel that in turn resulted in a hard/martensitic structure. Numerically estimated values of surface temperature, surface hardness and hardened depth as a function of laser processing parameters are in a good agreement with experimental results. Laser processing charts indicating expected values of surface temperature, surface hardness and hardened depth as a function of different wider range of laser processing parameters are proposed.
Predictive modeling of multi-track laser hardening of AISI 4140 steel
Materials Science and Engineering: A, 2008
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 threedimensional 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.
International Journal of Computational Materials Science and Surface Engineering, 2013
This study develops a thermodynamic model to investigate the quasi-steady thermal process of a wide thin steel workpiece irradiated with a moving Gaussian laser beam. Equations are established for temperature distribution, transformation boundaries, homogenisation time of austenite and cooling rate. The equations are numerically solved with an error of less than 10-8. The temperature distributions for various thicknesses are compared with that for infinite thickness at different laser traverse speed. The lag of the peak temperature relative to the centre of laser beam is found to be limited. The conditions to produce full and partial martensite are investigated. The model is verified by comparing the calculated Ac 1 and Ac 3 depths and temperature cycles with the experimental results. For AISI 4340 steel, correction coefficients are applied to the model to produce an empirical equation for temperature cycles above 488.4°C.
Laser hardening process simulation for cast iron
9TH NATIONAL CONFERENCE ON RECENT DEVELOPMENTS IN MECHANICAL ENGINEERING [RDME 2021], 2022
Laser hardening is one of the most sought after and innovative methods used for surface hardening and can be applied to a vast range of metallic materials. This process enables high quality and accurate results due to the controllability of input parameters. The laser beam is focused on a localized region for hardening that region. High intensity laser beam is used to heat up the surface to the austenitic region. There are steep temperature gradients that arise because of heat changes that ultimately result in cooling through conduction. The hardened martensitic region is determined by the heat distribution caused by the intensity profile of the laser beam. Simulations are a very important aspect of laser hardening as it gives us optimal conditions to use and provide us with results after varying parameters. After analyzing simulation results, we can select appropriate conditions to carry out our hardening process. This paper is a review of the fundamentals of the laser hardening process. The aim of this research work is to find an average of the case depth of the materials Cast Iron, and then further find the optimum conditions for both the materials under which laser hardening should be performed ideally.
A Fundamental Study of Laser Transformation Hardening
Metallurgical Transactions A, 1983
A theoretical and experimental study of heat flow and solid-state phase transformations during the laser surface hardening of 1018 steel was conducted. In the theoretical part of the study, a three-dimensional heat flow model was developed using the finite difference method. The surface heat loss, the temperature dependence of the surface absorptivity, and the temperature dependence of thermal properties were considered. This heat flow model was verified with the analytical solution of Jaeger and was used to provide general heat flow information, based on the assumptions of no surface heat loss, constant surface absorptivity, and constant thermal properties. The validity of each of these three assumptions was evaluated with the help of this heat flow model. In the experimental part of the study, on the other hand, a continuous-wave CO2 laser of 15 kW capacity was used in conjunction with a beam integrator to surface harden 1018 steel plates. The beam power and the travel speed of the workpiece were varied, and the onset of surface melting was determined. The configurations of the heat-affected zone observed were compared with those calculated using the heat flow model. The microstructure of the heat-affected zone was explained with the help of the calculated peak temperature, heating, and cooling rates.
Modelling of temperature evolution on metals during laser hardening process
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To achieve a precise and controlled laser process, an exhaustive analysis of the thermal behaviour of the material is necessary. In the present paper, a numerical simulation of the laser hardening process has been developed using both analytical solutions and the ®nite element code ANSYS TM to solve the heat transfer equation inside the treated material. The knowledge of the thermal cycles has enabled suitable processing parameters to be ascertained thus improving surface properties when metallic alloys have been irradiated. A simpler analytical method is also used to determine the mentioned parameters more quickly. This general purpose method has been applied to a speci®c experimental situation, namely the treatment of cylindrical pieces used in a multistage pump rotary jacket. #
Experimental and Numerical Study of AISI 4130 Steel Surface Hardening by Pulsed Nd:YAG Laser
Materials
Laser surface transformation hardening (LSTH) of AISI 4130 was investigated by a Nd:YAG pulsed laser. Laser focal height (LFH), pulse width (LPW), scanning speed (LSS), and power (LP) varied during the experiments. The microstructure of the treated zone was characterized by optical (OM) and field emission scanning electron microscopy (FESEM). Micro-hardness was measured in the width and depth directions. Results showed that the hardness and depth of hardened layer increased by decreasing the LSS and the laser focal position (LFP), and by increasing the LPW. The results were compared with those obtained by furnace heat treatment of the same steel. Eventually, a finite element model was employed for the simulation of the LSTH of AISI 4130 steel and calculation of the heat-treated zone. The results showed that the model can predict with accuracy the temperature profile and the size and the shape of the laser hardened region.