Christian Doppler Laboratory

          Early Stages of Precipitation

Christian Doppler Laboratory

          Early Stages of Precipitation

 

 

Project manager: Christoph Lerchbacher

 

Chromium Hot-work tool steels and plastic mould steels are commonly used for hot-work applications as for example die-casting dies or forging dies. These applications go hand in hand with the requirement of the resistance to the exposure to higher temperatures without changing microstructure and mechanical properties. These material properties can be achieved by a well-defined chemical composition, a high micro cleanness and a well-defined heat treatment. The heat treatment consists of an austenitization treatment with a subsequent hardening and a multiple tempering procedure. The hardened microstructure consists of a martensitic matrix with a few primary carbides and small amounts of retained austenite. Tempering causes the transformation of retained austenite into cubic martensite and cementite and the precipitation of a variety of secondary carbides, responsible for the high-temperature properties.
Quenching rate dependent mechanical properties after tempering lead to a need of the investigation of the hardened microstructure and its influence on the tempering behaviour. High resolution characterization methods like atom probe tomography (APT) are used to depict microstructural changes during hardening and the early stages of precipitation.