Prediction of phase transformations during laser surface hardening of AISI 4140 including the effects of inhomogeneous austenite formation

Mioković, T.; Schulze, Volker; Vöhringer, O.; Löhe, D.

doi:10.1016/j.msea.2006.07.037

Cited by 87 publications

(30 citation statements)

References 10 publications

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“…The optimization of laser surface hardening processes has so far largely been based on correlating process parameters to post-treatment properties and residual stress states of the component. [11][12][13][14][15][16][17] A large step towards a deeper process understanding can be reached if a real-time insight into the complex and fast thermo-mechanical processes during laser surface hardening can be obtained. As will be shown in the following, synchrotron-based x-ray diffraction offers a viable approach.…”

Section: Introductionmentioning

confidence: 99%

Fastin situphase and stress analysis during laser surface treatment: A synchrotron x-ray diffraction approach

Kostov

Gibmeier

Wilde

et al. 2012

Review of Scientific Instruments

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An in situ stress analysis by means of synchrotron x-ray diffraction was carried out during laser surface hardening of steel. A single exposure set-up that based on a special arrangement of two fast silicon strip line detectors was established, allowing for fast stress analysis according to the sin2ψ x-ray analysis method. For the in situ experiments a process chamber was designed and manufactured, which is described in detail. First measurements were carried out at the HZG undulator imaging beamline (IBL, beamline P05) at the synchrotron storage ring PETRA III, DESY, Hamburg (Germany). The laser processing was carried out using a 6 kW high power diode laser system. Two different laser optics were compared, a Gaussian optic with a focus spot of ø 3 mm and a homogenizing optic with a rectangular spot dimension of 8 × 8 mm2. The laser processing was carried out using spot hardening at a heating-/cooling rate of 1000 K/s and was controlled via pyrometric temperature measurement using a control temperature of 1150 °C. The set-up being established during the measuring campaign allowed for this first realization data collection rates of 10Hz. The data evaluation procedure applied enables the separation of thermal from elastic strains and gains unprecedented insight into the laser hardening process.

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Section: Introductionmentioning

confidence: 99%

Fastin situphase and stress analysis during laser surface treatment: A synchrotron x-ray diffraction approach

Kostov

Gibmeier

Wilde

et al. 2012

Review of Scientific Instruments

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“…In the transition zone, a thin layer can be spotted. This effect is already known and described by Mioković [19]. This kind of layer is a result of the transformation kinetics.…”

Section: Resultsmentioning

confidence: 59%

“…Bailey et al [11] added a diffusion model to a thermal finite element method (FEM) analysis to predict the hardness as well as the stresses of laser hardened 42CrMo4 (AISI 4140). Mioković et al [19] researched the effect of the austenitisation process as well as the martensitic kinetics. Tobar et al [14] implemented an even more complex model of the metallurgical effect in laser hardening.…”

Section: Introductionmentioning

confidence: 99%

Optimization of the Laser Hardening Process by Adapting the Intensity Distribution to Generate a Top-hat Temperature Distribution Using Freeform Optics

2017

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Laser hardening is a surface hardening process which enables high quality results due to the controllability of the energy input. The hardened area is determined by the heat distribution caused by the intensity profile of the laser beam. However, commonly used top-hat laser beams do not provide an ideal temperature profile. Therefore, in this paper the beam profile, and thus the temperature profile, is optimized using freeform optics. The intensity distribution is modified to generate a top-hat temperature profile on the surface. The results of laser hardening with the optimized distribution are thereupon compared with results using a top-hat intensity distribution.

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“…[12], [14], and [15] into Eq. [13] and simplifying the relation, the fraction of ferrite and e-carbide is defined as…”

Section: B Thermokinetic Modelmentioning

confidence: 99%

“…More detailed research has also been performed on defining the effect of process parameters on phase transformation during the heat treatment of materials. [10][11][12] Obviously, reaching a specific microstructure or hardness level in the buildup requires understanding of the temperaturephase transformation relation.…”

Section: Introductionmentioning

confidence: 99%

Thermokinetic Modeling of Phase Transformation in the Laser Powder Deposition Process

Foroozmehr

Kovacevic

2009

Metall Mater Trans A

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A finite element model coupled with a thermokinetic model is developed to predict the phase transformation of the laser deposition of AISI 4140 on a substrate with the same material. Four different deposition patterns, long-bead, short-bead, spiral-in, and spiral-out, are used to cover a similar area. Using a finite element model, the temperature history of the laser powder deposition (LPD) process is determined. The martensite transformation as well as martensite tempering is considered to calculate the final fraction of martensite, ferrite, cementite, e-carbide, and retained austenite. Comparing the surface hardness topography of different patterns reveals that path planning is a critical parameter in laser surface modification. The predicted results are in a close agreement with the experimental results.

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Prediction of phase transformations during laser surface hardening of AISI 4140 including the effects of inhomogeneous austenite formation

Cited by 87 publications

References 10 publications

Fastin situphase and stress analysis during laser surface treatment: A synchrotron x-ray diffraction approach

Fastin situphase and stress analysis during laser surface treatment: A synchrotron x-ray diffraction approach

Optimization of the Laser Hardening Process by Adapting the Intensity Distribution to Generate a Top-hat Temperature Distribution Using Freeform Optics

Thermokinetic Modeling of Phase Transformation in the Laser Powder Deposition Process

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