Contact Persons:

Dr. Julia Kristin Hufenbach

Dr. Uta Kühn

High-strength Steels

Steel is by far the most widely used metallic construction material due to its wide range of properties and variety of applications. Due to a tailored adjustment of the chemical composition as well as the control of the processing parameters, high-performance materials for different areas of application can be prepared. Thereby, the innovation potential of steel is still far from being exhausted.

At all times, steels play a key role in tool manufacturing. The increasing standards for the processing of novel high-performance materials as well as the general demand for longer service lifes and more efficient processes are the challenges for tool making in the future. Tool steels for high-tech applications have to meet a multitude of requirements like high hardness, wear-resistance, toughness, compression and fatigue strength.

With this aim, the IFW Dresden develops load-adapted alloys and tailored resource-saving, efficient manufacturing technologies. For preparing the iron-based alloys, pure elements and high solidification rates are applied. Thereby, thermodynamical and kinetical aspects promote the formation of the non-equilibrium phases martensite, retained austenite as well as complex carbides already in the as-cast state (Fig. 1 and Fig. 2) [1-5].

Fig. 1: Optical micrograph of the microstructure of a Fe85Cr4Mo4.8V2W2.8C1.4 alloy (etched with Beraha).
Fig. 2: Scanning electron micrograph showing the carbide network of a Fe85Cr4Mo8V2C1 alloy (deep-etched).

The combination of phases results for the Fe85Cr4Mo8V2C1 (wt%) in a high yield (≈ 2000 MPa) and ultimate strength (≈ 4000 MPa) under compressive load as well as in a high fracture strain of about 12% [1]. The strength and deformation values of the cast FeCrMoVC alloy, which are determined in the compression test, thereby exceed the values of many conventional, heat-treated tool steels (Fig. 3). 

Fig. 3: Comparison of the engineering stress-strain curves of a Leibniz-Steel and a conventional tool steel (1.2379).

Furthermore, the alloys Fe92.7Cr4.2V2.1C1 [2, 5] and Fe85Cr4Mo1V1W8C1 [3] reveal a pronounced deformation-induced transformation of austenite into martensite (TRIP effect). The alloys show compression strengths of almost 5000 MPa combined with a fracture strain of over 20% as well as an extremely high energy absorption capacity under compressive load.

Out of the developed alloys, prototype tools can be prepared in a near-net-shape casting process (Fig. 4) and by selective laser melting (Fig. 5) [6]. Industrial tests showed that the novel alloys in combination with the applied production process lead to a significant increase of the tool life compared to conventionally used steels.

Another potential area of application for the presented Leibniz-Steels is the use as filler material. Within the framework of the ZIM project “EISI” (founded by Federal Ministry for Economic Affairs and Energy) innovative filler materials are developed and implemented in the repair and the deposition welding process of high-performance tools (Fig. 6).

Fig. 4: Cutting tool (l.) and bucket teeth (r.) out of IFW-Steel.
Fig. 5: Drill with integrated cooling channels out of novel tool steel manufactured by selective laser melting.
Fig. 6: Welding wire out of an iron-based alloy manufactured at IFW Dresden (l.); scanning electron micrograph of the cross-section of a laser deposition welding with Fe85Cr4Mo8V2C1 alloy (r.).

Selected publications

[1] U. Kühn, N. Mattern, T. Gemming, U. Siegel, K. Werniewicz, J. Eckert: Appl. Phys. Lett. 90 (2007) 261901.

[2] U. Kühn, J. Romberg, N. Mattern, H. Wendrock, J. Eckert: J. Mater. Res. 25 (2010) 368.

[3] J. Hufenbach, L. Giebeler, M. Hoffmann, S. Kohlar, U. Kühn, T. Gemming, S. Oswald, B. Eigenmann, J. Eckert: Acta Mater. 60 (2012) 4468.

[4] J. Hufenbach, S. Kohlar, U. Kühn, L. Giebeler, J. Eckert: J. Mater. Sci. 47 (2012) 267.

[5] J. Hufenbach, K. Kunze, L. Giebeler, T. Gemming, H. Wendrock, C. Baldauf, U. Kühn, W. Hufenbach, J. Eckert: Mater. Sci. Engin. A 586 (2013) 267.

[6] J. Sander, J. Hufenbach, L. Giebeler, H. Wendrock, U. Kühn, J. Eckert: Mater. Des. 89 (2016) 335.