Heat treatment is an essential tool to adjust the desired properties of steels. The typical heat treatment of martensitic stainless steels consists of hardening and subsequent tempering once or several times. During tempering the common tempering mechanisms occur, such as carbide precipitation, relaxation of the fresh martensite, destabilisation of the retained austenite and subsequent transformation of austenite into martensite. However, certain parameters can also lead to the opposite reaction in the retained austenite, i.e. the retained austenite is stabilised by diffusion of carbon from the martensite into austenite. This partitioning effect can occur especially, if the component to be heat treated is not completely cooled down to the desired quenching temperature before the tempering step starts. Such derivations in the quenching temperature can lead to an increased retained austenite content and a lower austenite stability in the final microstructure. For low alloy steels, stabilisation of a larger amount of retained austenite has long been applied and is known as quenching and partitioning.
In this study, the effect of partitioning on the retained austenite in the final state of the component and the corresponding properties of the material were investigated. For this purpose, samples were heat treated by dilatometer as well as in furnaces in order to set a specific retained austenite content in the microstructure after tempering. This is mainly possible by varying the quenching temperature in combination with different tempering temperatures. Even small temperature variations can have an influence on the retained austenite content. After the heat treatment of the samples, the properties were determined and the values compared with each other. Additional microstructure investigations included, XRD, SEM and optical metallography.