In situ carbide formation causing strain-age cracking in additively manufactured, highly alloyed steels

Journal of Materials Research and Technology, vol. 35, pp. 4457–4472

Abstract

Since its conception in the early 1990s, additive manufacturing of metallic materials has evolved into a staple manufacturing technique in various industries. Among other process-specific advantages, such as sustainability and geometric freedom, the unique thermal conditions of extremely fast heating and cooling cycles can allow for the manufacturing of alloy systems facing challenges in conventional processing or eliminate the need for further heat treatments. This holds true for Fe–Mn–Al–C steels, which exhibit extraordinary strength and ductility due to κ-carbide precipitation but encounter challenges during casting and demand extensive heat treatments. In this study, we set out to achieve in situ κ-carbide precipitation within an X110MnAl30-8 steel by manipulating the thermal history of the laser-based directed energy deposition process. Using CALPHAD calculations to determine suitable heat treatment temperatures, a preheating setup was developed, which allowed for the precise adjustment and measurement of the temperature development within the samples. Subsequently, different preheating temperatures were evaluated for potential in situ κ-carbide precipitation. Preheating the substrate plate to 500 °C resulted in κ-carbide formation in the as-built material. Simultaneously, the formation of grain boundary cracking was observed. Similar to the strain-age cracking phenomenon in Ni-base alloys, the rapid formation of κ-carbides at grain boundaries leads to the weakening of grain boundaries.

Authors 5

1. Jan-Simeon Ludger Bernsmann Aachen Digital Additive Production (DAP)

   RWTH Aachen University

   Affiliation as printed

   Digital Additive Production, RWTH Aachen University, Campus-Boulevard 73, 52074, Aachen, Germany

2. Fabian Kies Aachen Steel Institute

   RWTH Aachen University

   Affiliation as printed

   Steel Institute, RWTH Aachen University, Intzestraße 1, 52072, Aachen, Germany

3. Jaqueline Gehlmann Aachen Central Facility for Electron Microscopy

   RWTH Aachen University

   Affiliation as printed

   Central Facility for Electron Microscopy, RWTH Aachen University, Ahornstraße 55, 52074, Aachen, Germany

4. Johannes Henrich Schleifenbaum Aachen Digital Additive Production (DAP)

   RWTH Aachen University

   Affiliation as printed

   Digital Additive Production, RWTH Aachen University, Campus-Boulevard 73, 52074, Aachen, Germany

5. Christian Haase corresponding

   Technische Universität Berlin

   Affiliation as printed

   Center for 3D Technologies, TU Berlin, Straße des 17. Juni 136, 10623, Berlin, Germany

   Chair Materials for Additive Manufacturing, TU Berlin, Ernst-Reuter-Platz 1, 10587, Berlin, Germany