WEB Nano structured steels for forging applicationTuesday (22.09.2020) 10:40 - 10:55 S: Structural Materials 1 Part of:
As many other industries relies the forging industries on high strength steels especially for automotive application. Martensitic quench and tempering alloys, like 42CrMo4 are commonly used, as these materials show a good balance of strength and impact toughness. Currently, these classic design properties are getting replaced by the cyclic material behavior. A different commonly used steel class are the precipitation hardening ferritic pearlitic steels, which achieve their final properties through a controlled cooling from the forging heat. However, these steels do not achieve the properties of quench and tempering alloys.
Recently a new type of martensitic steels was introduced, which achieve their final properties through air cooling out of the forging heat and therefore combine the properties of quench and tempering alloys with the reduced process route of precipitation hardening ferritic pearlitic steels. These materials were pushed to market maturity and are now standardized under the European material number 1.5132.
Through the usage of diffusion inhibiting elements like manganese and boron not only martensitic microstructures can be achieved. Additionally, carbide predecessor phases as well as retained austenite are formed on the nanometer scale. These features lead to high strengths and additionally to comparable good ductility. Especially the cyclic strengths levels are 50% higher compared to the reference alloy 42CrMo in the quenched and tempered state. As the particles are too small to be identified by light optical microscopy (LOM) or scanning electron microscopy (SEM) atomprobe tomography (APT) and synchrotron x-ray diffraction was used in this study (SYXRD). Furthermore, the cyclic strength of five different laboratory melts is correlated with the morphology of precipitates which were investigated by SEM and transmission electron microscopy (TEM).