Laser Hardening Process Research Articles

Time-dependent 3D modeling of the thermal analysis of the high-power diode laser hardening process

In this paper, the thermal analysis of the high-power diode laser hardening process was modeled on AISI 4130 steel. Afterward, the depth and width of hardness were predicted based on the complete austenite temperature (AC3). Due to the dimensions and output beam power of the diode laser stack (DLS), it is impossible to achieve the suitable power density (103-105 W/cm2). Furthermore, the output intensity profile of the DLS is not homogeneous because of the pitch between the emitters. Thus, to achieve a suitable power density and a uniform beam profile, an optical layout was designed. The beam profile was experimentally obtained by a beam profiler at different distances from the focal plane and was compared with the modeling results. Due to the agreement between the modeling and experimental results, the intensity value of each mesh of the laser profile was extracted from the ZEMAX software. Then, for the thermal analysis of the laser hardening process (LHP), it was entered as a heat flux input into the COMSOL Multiphysics software.

Experimental investigation and effects of laser hardening process parameters on microhardness of En24 steel

In presented paper through experimental investigation is carried out with fiber laser system so as to evaluate the effects of laser surface hardening process parameters on the microhardness (width and depth) of the laser treated En24 steel using a Taguchi method. The optical microscope and microhardness tester is used to examine the microstructure, microhardness (width and depth) of the laser hardened samples across the heat affected zone. The selected process parameters were laser beam power (210, 225 and 300 W), laser scanning speed (1.0, 5.5 and 10.0 mm/s) and standoff distance (175, 200 and 225 mm) respectively. The laser treated hardened surface layer has a microhardness of 728.1 HV0.3 and reached a microhardness depth of 2471.44 µm, which is twice as high as untreated samples of En24 steel. From this study, it can be summarized that the microhardness of laser treated samples is maximized by controlling laser beam power, laser scanning speed and standoff distance, which improves the service life of laser-treated En24 steel components. The percentage error within the acceptable range was found to be small and was obtained by comparing the microhardness values obtained from the experimental results and predicted microhardness values obtained by using nonlinear regression equation.

Effects of laser hardening process parameters on hardness depth of Ck45 steel using Taguchi’s optimization technique

Laser hardening is one of the reasonable procedures utilized to improve surface mechanical and wear resistance of target materials. This process is easy to use for improving surface properties of complex shape components with minimum time requirement. The beauty of this process is that it is possible to improve only selective surface properties without altering the remaining surface properties of bulk material. Ck45 steel has various important properties like hardness, superior wear resistance and frictional performance etc. These properties are useful in various industrial applications. The existing study is an attempt to analyse results on surface properties with the aid of process parameters of a laser hardening process on hardness depth and microstructure of laser hardened Ck45 steel the use of a design of experimental approach. From this analysis, it can be summarized that the depth of the surface layer hardness is maximized by controlling the laser beam power, laser scan speed and standoff distance, which improves the service life of Ck45 steel components hardened by laser. Comparing the experimental consequences with the effects of L9 orthogonal array approach, the proportion error was observed to be negligible with a higher co-relation coefficient (r2) of 0.905.

An Optimal Genetic Algorithm for Fatigue Life Control of Medium Carbon Steel in Laser Hardening Process

This study proposes a genetic algorithm-optimized model for the control of the fatigue life of AISI 1040 steel components after a high-power diode laser hardening process. First, the effect of the process parameters, i.e., laser power and scan speed, on the fatigue life of the components after the laser treatment was evaluated by using a rotating bending machine. Then, in light of the experimental findings, the optimization model was developed and tested in order to find the best regression model able to fit the experimental data in terms of the number of cycles until failure. The laser treatment was found to significantly increase the fatigue life of the irradiated samples, thus revealing its suitability for industrial applications. Finally, the application of the proposed genetic algorithm-based method led to the definition of an optimal regression model which was able to replicate the experimental trend very accurately, with a mean error of about 6%, which is comparable to the standard deviation associated with the process variability.

Direct laser hardening of AISI 1020 steel under controlled gas atmosphere

Laser hardening is usually performed in air. Use of a controlled gas atmosphere might produce a direct reaction of the gas with surface and thus provide an opportunity to engineer the surface microstructures. However, few studies are reported on direct gas-assisted laser hardening process. In this paper, a direct gas-assisted laser hardening is demonstrated on AISI 1020 steel using an ytterbium-doped fiber laser in presence of four different gases – air, argon, carbon dioxide and propane. All hardening trials were conducted at same laser parameters and only the gas was changed to evaluate its effect on hardness and microstructure of the steel. Results show that argon had slightly higher hardening effect than air as it prevents surface oxidation. Propane produced a very high surface hardness (914 HV) compared to conventional laser hardening process (395 HV). The ultrahigh hardness is due to diffusion of carbon into steel from decomposed propane. Increasing the concentration of propane contributed to an increment in hardness primarily due to large amount of carbides in near surface region. Contrarily, carbon dioxide yielded a lower surface hardness (350 HV) despite its high carbon content. This is attributed to the oxidizing effect of carbon dioxide, which produces decarburization during laser processing. The study reveals the potential of using direct gas-assisted laser hardening technique to alter surface mechanical properties of steel.

Laser surface hardening of engine camshaft cams

The publication describes research into the laser hardening process of the camshaft cams surface. Samples of camshaft cams made of structural bearing steel were hardened using a powerful fiber laser LS-15. The effect of altering the laser surface hardening process parameters on the microstructure and microhardness of the surface was investigated. Also, the influence of low-temperature tempering after laser surface hardening was shown.

Modeling the temperature distribution during laser hardening process

A mathematical model has been developed here to calculate the temperature distribution on the surface and bulk of a steel plate under the laser hardening process. The model starts from the basic heat equation, is then developed to a volumetric form and is connected to the various solid phases existing. The model is based on two strongly influencing parameters of the laser hardening process: velocity of the laser spot and irradiation time. The results are compared to the available experimental data reported in the literature. The volumetric model provides an assessment of temperature distribution in both the vertical and horizontal axis. Laser irradiation at sufficiently high fluence can be used to create a solid state phase change on the surface. Primary calculations show that the temperature profile has a Gaussian distribution in horizontal x-and y-axis and presents an exponentially decreasing distribution in the horizontal and vertical depth directions.

WITHDRAWN: Modeling the temperature distribution during laser hardening process

WITHDRAWN: Modeling the temperature distribution during laser hardening process

An experimental investigation of the effects of diode laser surface hardening of AISI 410 stainless steel and comparison with furnace hardening heat treatment

This study investigated the ability of the continuous wave diode laser surface hardening of AISI 410 martensitic stainless steel with a maximum power of 1600 W. Variable process parameters scanning speed (4–7 mm/s), laser power (1200–1600 W) and stand-off distance (65–75 mm) were considered in this study. Microhardness, the geometry of hardened layer (depth and width), microhardness deviation from the base metal microhardness (MHD), microstructure analysis of the laser-hardened zone through optical microscopy and field emission scanning electron microscopy and percentage of the ferrite phase in AISI 410 microstructure by using Clemex software were considered as process output responses. Results confirmed that by increasing the laser power and reducing the scanning speed, the surface hardness and the depth of hardness increase. It is also revealed the width of the hardened area increases by enhancing stand-off distance and reducing the laser power. Maximum hardness of 630 HV0.3 with 2.2 mm depth is obtained. Also, the furnace hardening heat treatment is compared with the laser hardening process. Microstructure, microhardness, and impact tests of the two processes are compared. Results showed that the hardness of the diode laser is 1.4 times the hardness of the furnace hardening heat treatment.

Special Issue: Highlights From ASME CIE 2018

Special Issue: Highlights From ASME CIE 2018

Status of laser transformation hardening of steel and its alloys: a review

The state of laser transformation hardening in surface modification of steel and its alloys is reported in this review paper. The laser hardening process involves the use of high-intensity laser radiation to heat the surface of steel into the austenitic region rapidly. Due to high rates of heat transfer, steep temperature gradients result in rapid cooling by conduction. This causes the transformation from an austenite to a martensite microstructure without the need for external quenching and generates a hard wear-resistant surface. The introduction of high-power lasers, such as neodymium-doped yttrium aluminum garnet (Nd:YAG), diode and fiber lasers, has made laser-assisted hardening an attractive candidate for surface hardening processes. Recently, fiber lasers appeared as a competitor to Nd:YAG and diode lasers for material processing. This review paper is a synopsis of the fundamentals of laser hardening, outlining some of its benefits compared with those of conventional hardening techniques and its industrial applications. A selective review of the experimental and numerical research carried out on steel in this area is also presented. Finally, it is concluded that the overall state of research on laser hardening in surface engineering of steel is well developed, and a still-growing industrial application is observed.

Enhancement of surface hardness and metallurgical properties of AISI 410 by laser hardening process; diode and Nd:YAG lasers

This paper investigates the experimental study of laser surface hardening (LSH) of AISI 410 martensitic stainless steel by using two industrial lasers; 1600 W high power diode laser and 700 W Nd:YAG laser. The influence of the distribution and shape of the laser beam; Top-hat in diode laser and Gaussian distribution in Nd:YAG laser, have been investigated on the micro-hardness, geometrical dimensions of the hardened area (depth and width), microhardness deviation (MHD) from the base metal in width and depth of hardened layer, and the ferrite phase percentage. Microstructure evaluation of the laser hardened zones were performed using optical and FE-SEM. Results show that the diode laser creates a higher surface hardness, more depth and width of hardness, more MHD in depth and width and less ferrite phase than the Nd:YAG laser, which is because of lower wavelength of diode laser (808 nm) than Nd:YAG laser (1064 nm) that lead to higher laser energy absorption. Observations indicate that hardened layer of diode laser is about 620 HV0.3 with 1.8 mm depth, while for Nd:YAG laser is about 598 HV0.3 with 0.211 mm depth.

Preliminary Study of Ultrasound-Assisted Laser Hardening of AISI H13 Tool Steel

This paper presents the viability of ultrasound in assisting the performance of laser hardening process. A nanosecond pulse laser was employed as a heat source in this study to heat and introduce hardened phase in AISI H13 tool steel. The influences of laser power and traverse speed on surface roughness and case depth of laser-irradiated region were experimentally investigated. The laser processing with the assist of ultrasound can improve the surface roughness of laser-hardened area by 7.5% and also increase the case depth by 7.65% compared to the non-ultrasound condition. Under a suitable processing condition, the laser can harden and polish the metal surface at the same when the ultrasound was incorporated in the process. The implication of this study will broaden the viability of ultrasound in the laser surface hardening/polishing of metals.

Nd:YAG laser hardening of AISI 410 stainless steel: Microstructural evaluation, mechanical properties, and corrosion behavior

In this paper, a pulsed Nd:YAG laser with a maximum power of 700 W, was utilised to investigate the laser surface hardening of AISI 410 martensitic stainless steel. Focal point position, scanning speed and pulse width were considered as process variable parameters. Corrosion behavior of laser surface hardened samples were investigated by IVIUMSTAT apparatus in a 3.5 wt% NaCl solution. Maximum microhardness, depth, and width of hardness and percentage of ferrite phase of metallographic and FESEM pictures were evaluated. Results show that surface hardness increased up to 762 HV. Results also reveal that the laser focal point position and pulse width are effective parameters in laser hardening process. In potentiodynamic polarization tests potential stated to increase at a rate of 1 mV/s from −0.4 V to 0.2 V. Results indicate that the corrosion resistance increased due to laser hardening process.

Temperature Field Numerical Analysis Mode and Verification of Quenching Heat Treatment Using Carbon Steel in Rotating Laser Scanning.

Temperature history and hardening depth are experimentally characterized in the rotational laser hardening process for an AISI 1045 medium carbon steel specimen. A three-dimensional finite element model is proposed to predict the temperature field distribution and hardening zone area. The laser temperature field is set up for an average distribution and scanned along a circular path. Linear motion also takes place alongside rotation. The prediction of hardening area can be increased by increasing the rotational radius, which in turn raises the processing efficiency. A good agreement is found between the experimental characterized hardness value and metallographic composition. The uniformity of the hardening area decreases with increasing laser scanning speed. The increased laser power input could help to expand the hardening depth.

Control Quality on Process of Laser Heat Treatment

Laser surface hardening, is a process in which a shaped laser beam is scanned across the surface to produce a hard and wear-resistant surface on components. Compared with the conventional surface hardening process, the laser heat treatment offers a number of attractive characteristics such as minimal part distortion, self-quenching and the need for less finishing work. The challenge of laser hardening is the uneven surfaces found in molds such as those with sharp edges or holes. In these cases, due to the differences in the surrounding volume of the material, overheating problems often appear leading to unacceptable treatment results. The purpose of this paper is to present the new technology, “raio” developed by Talens System for laser hardening process. This technology is able to adapt to geometrical singularities of the components to be treated, ensuring the dimensions of the hardened area and hardness values are compliant with the requirements. The main features of the technology for laser hardening are validated on a set of samples of 1.2738 steel with representative discontinuities of molds. Mechanical and microstructural characterizations of the hardened cross sections confirm the advantages of the raio technology in regard to the quality compliance of the laser hardening process. Furthermore, raio offers the same advantages for other laser processes, like softening of critical area or laser cladding for repairing of damaged components.

Microstructural and Mechanical Properties Examination of High-Power Diode Laser-Treated R260 Grade Rail Steels Under Different Processing Temperatures

In the present study, high-power diode laser surface treatment was implemented to R260 grade steel with three different processing temperatures (1100 °C, 1200 °C, and 1300 °C) at the laser power of 1750 W and scanning speed of 6 mm/s, in order to identify the effect of various processing temperatures on the mechanical performance. According to the test results, the laser-treated sample at 1300 °C showed much better mechanical performance among the other laser-treated samples. It was found that the laser-treated sample at 1300 °C had about 3 times more surface hardness, a 43 pct increase in yield strength, and a 53 pct increase in toughness value compared to the untreated sample. Microstructural investigations showed that this surface treatment did not only generate a martensitic structure with a certain depth but also provided the formation of a fine pearlitic structure contributing to an increase in the mechanical properties. As a conclusion, it was found that the processing temperature is one of the critical factors affecting the mechanical properties in the laser hardening process. Moreover, the results demonstrated that this treatment method might be an alternative method to enhance the mechanical properties of existing rail steels online without the need for rail disassembly, reducing operational costs.

Effects of Prior Microstructure and Heating Rate on the Depth of Increased Hardness in Laser Hardening: Comparison of Computer Simulation and Experimental Results

The response of the hypo-eutectoid steel to laser hardening, which is measured as the depth of the increased hardness, depends not only on the set of the process parameters but also on the prior microstructure of the workpiece. The multiple preliminary stages of the treatment of the workpiece in the industrial conditions are commonly not completely known, resulting in an unclear prior microstructure of the workpiece. To model the response of the hypo-eutectoid steel, a validated numerical model for laser hardening has been used in the computer simulation of the process for four different cases. The numerical model takes into account the 3D geometry of the workpiece, its prior microstructure, and the effect of the heating rate during the laser hardening process on the kinetics of the phase transformation. The four cases were designed to take into account two different sets of process parameters and two different prior microstructures of the workpiece. The output of the computer simulation was verified experimentally.

Experimental Study on Effect of Laser Hardening Parameters on Carbon Steel, Non-Malleable Cast iron and X20Cr13 Materials

Laser hardening is a surface heat treatment process used to enhance tribological and mechanical properties of metals which also leads to increase in service life of the components. Material removal, wear and tear, load concentration occurs mostly at rotating and reciprocating parts. Hence it is sufficient to enhance the hardness of a component at functional areas rather than the entire component. Laser hardening process is designed to change the microstructure of metals through controlled heating and cooling to get a modified surface. The constraints of traditional surface heat treatment process such as inability to treat specific area, distortion, poor degree of controllability, requirement of a quenching medium, long cycle time can be overcome by using Laser surface heat treatment and in addition to that it can be automated. With its benefits Laser surface hardening turns out to be a cost effective and energy saving process. The presented work is an investigation of the laser surface hardening via experimental results making use of a 6 axis robotic arm and a 10KW high power diode laser system as heat source with a wavelength of 980nm on leading automotive parts such as retainer, hub, and turbine blade whose materials being non-malleable cast iron, carbon steel, X20Cr13 respectively. Process parameters such as laser power from power source, scan speed were varied to understand the influence on resulting heat treated surface and efforts were made to optimize the process parameters to attain maximum hardness for the component to enhance its working life.

High precision laser hardening method using dummy irradiation for small and thin parts: fundamental study on hardening and deformation

ABSTRACTA laser hardening process has received much attention because of its ability as a local heat treatment method without requiring a cooling solution. A local heat treatment with a small power density can result in the small deformation of the workpiece that can be performed without a post-process for finishing. However, such superior features can be demonstrated in the case of a workpiece with a large volume and a heat capacity for self-cooling. Small and thin parts such as brake disks and miniature guide rails might not have enough volume or heat capacity to show the features. Therefore, we propose a novel method that completes the heat treatment and deformation-less processes only using a laser. The method has a laser irradiation for hardening and another one for deformation correction. In the present paper, we carried out a fundamental study on hardening and deformation and demonstrated the potential of the proposed method.