Mechanical properties of AlXFeY intermetallics in Al-base coatings on steel 22MnB5 and resulting wear mechanisms at press-hardening tool steel surfaces

Windmann, M.; Röttger, Arne; Hahn, Isabel; Theisen, W.

doi:10.1016/j.surfcoat.2017.04.075

Cited by 31 publications

(19 citation statements)

References 23 publications

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“…For instance, Wang and Chen [12] studied the oxidation behaviour of Al-Si coated steels between 750 and 950 °C and observed that a high dwell time results in the diffusion of more iron from the steel to the surface coating, accompanied by intermetallic phase transformations. Among these phases, the formation of binary Fe-Al phases such as Fe 4 Al 13 , Fe 2 Al 5 , FeAl 2 and FeAl, was reported [15,16]. Grigorieva et al [6] studied the phase transformations occurring during an austenitization step at 900 -930 °C by Energy Dispersive X-ray Spectrometry (EDS) analysis of a cross-section, after interrupting the heat treatment at several temperatures.…”

Section: Figure 1 Schematic Illustration Of a Typical Hot-stamping Linementioning

confidence: 99%

In situ surface imaging: High temperature environmental SEM study of the surface changes during heat treatment of an Al Si coated boron steel

Barreau

Méthivier

Sturel

et al. 2020

Materials Characterization

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Al-Si coated boron steels have been of interest for many years because of their superior mechanical properties and their excellent oxidation resistance. These high strength steels are particularly used in hot stamping processes during which the Al-Si coating undergoes multiple microstructural transformations. In this study, morphology and structure transformations are investigated using an original approach. Most of the time, the coating evolution is studied in cross section, by ex situ characterization of its different layers after heat treatment. In this work, the evolution of the surface is explored for the first time using in situ high-temperature Environmental Scanning Electron Microscopy (HT-ESEM). The austenitization step reproduced in the ESEM chamber allows a precise description of several surface changes occurring, depending on the temperature range. Among them, the main change in morphology is occurring between 650 and 800 °C and is linked to different reactions between aluminium and bi-and ternary Fe-Al-Si phases. The heating rate is also pointed out as a key parameter that affects the surface morphology. In fact, with low heating rates the surface is mostly composed of hexagonal and rectangular elements coming from t 5 (Fe 2 Al 8 Si) structuration, while needle-shaped FeAl 3 structures are found for higher heating rates. In addition, it is observed that the heating rate also affects the surface roughness depending on the surface morphology. Finally, the origin of the presence of micrometrics pores appearing between 800 and 900 °C at the coating surface is discussed. Our hypothesis supported by ex situ characterization is that they result from formation of a crystallized oxide layer, probably close to a-Al 2 O 3 structure.

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Section: Figure 1 Schematic Illustration Of a Typical Hot-stamping Linementioning

confidence: 99%

In situ surface imaging: High temperature environmental SEM study of the surface changes during heat treatment of an Al Si coated boron steel

Barreau

Méthivier

Sturel

et al. 2020

Materials Characterization

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“…Abrasive wear in press hardening takes place due to the formation of abrasive particles flaked from the coating in the sheet metal, as well as interaction with sheet asperities [ 20 , 22 , 23 ]. Abrasive wear results in net loss of shape of the tool in the most affected zones, resulting in poor contact which is detrimental to component cooling.…”

Section: Resultsmentioning

confidence: 99%

Pilot Demonstration of Hot Sheet Metal Forming Using 3D Printed Dies

Pujante¹,

González

Garcia-Llamas³

2021

Materials

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Since the popularization of press hardening in the early noughties, die and tooling systems have experienced considerable advances, with tool refrigeration as an important focus. However, it is still complicated to obtain homogeneous cooling and avoid hot spot issues in complex geometries. Additive Manufacturing allows designing cavities inside the material volume with little limitation in terms of channel intersection or bore entering and exit points. In this sense, this technology is a natural fit for obtaining surface-conforming cooling channels: an attractive prospect for refrigerated tools. This work describes a pilot experience in 3D-printed press hardening tools, comparing the performance of additive manufactured Maraging steel 1.2709 to conventional wrought hot work tool steel H13 on two different metrics: durability and thermal performance. For the first, wear studies were performed in a controlled pilot plant environment after 800 hot stamping strokes in an omega tool configuration. On the second, a demonstrator tool based on a commercial tool with hot spot issues, was produced by 3D printing including surface-conformal cooling channels. This tool was then used in a pilot press hardening line, in which tool temperature was analyzed and compared to an equivalent tool produced by conventional means. Results show that the Additive Manufacturing technologies can be successfully applied to the production of press hardening dies, particularly in intricate geometries where new cooling channel design strategies offer a solution for hot spots and inhomogeneous thermal loads.

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“…The number of voids was estimated from the coating cross-sections. Windmann et al [36] determined the hardness values of several Al x Fe y intermetallics at different temperatures. A linear fit between hardness and temperature was obtained for various intermetallics (Fig.…”

Section: Materials Propertiesmentioning

confidence: 99%

Multiscale friction model for hot sheet metal forming

et al. 2021

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The accurate description of friction is critical in the finite element (FE) simulation of the sheet metal forming process. Usually, friction is oversimplified through the use of a constant Coulomb friction coefficient. In this study, the application of an existing multiscale friction model is extended to the hot stamping process. The model accounts for the effects of tool and sheet metal surface topography as well as the evolution of contact pressure, temperature, and bulk strain during hot stamping. Normal load flattening and strip drawing experiments are performed to calibrate the model. The results show that the model can relatively well predict friction in strip draw experiments when the tool surface evolution due to wear is incorporated. Finally, the application of the formulated multiscale friction model was demonstrated in the FE simulation of a hot-stamped part.

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Mechanical properties of AlXFeY intermetallics in Al-base coatings on steel 22MnB5 and resulting wear mechanisms at press-hardening tool steel surfaces

Cited by 31 publications

References 23 publications

In situ surface imaging: High temperature environmental SEM study of the surface changes during heat treatment of an Al Si coated boron steel

In situ surface imaging: High temperature environmental SEM study of the surface changes during heat treatment of an Al Si coated boron steel

Pilot Demonstration of Hot Sheet Metal Forming Using 3D Printed Dies

Multiscale friction model for hot sheet metal forming

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