THE INFLUENCE OF Q&P PARAMETERS ON CARBIDE PRECIPITATION AND MECHANICAL PROPERTIES OF HIGH-CR MARTENSITIC STEEL

Quenching and Partitioning method of steel heat treatment (Q&P) [1-4] consists of two steps: partial martensitic quenching (Q) followed by short annealing i.e. partitioning step (P). During partitioning carbon atoms diffuse from supersaturated martensite laths or plates into surrounding untransformed austenite. This process leads to the stabilisation of retained austenite in steel after martensitic transformation. As a result, a two-phase microstructure is obtained. It consists of tempered martensite and stable retained austenite. The presence of stabilised austenite in steel improves the ductility of steel due to the TRIP effect (Transformation Induced Plasticity). The aim of this study was to design the parameters of Quenching and Partitioning (Q&P) process of X46Cr13 steel and to investigate the influence of the process parameters on the microstructure and on mechanical properties of this steel. The parameters of Q&P treatment were determined with the use of dilatometric measurements. To determine phase composition after Q&P process, magnetic measurements were conducted. The microstructure of martensite and austenite as well as the presence of carbides were examined through Transmission Electron Microscopy (TEM). Changes in hardness after various variants of Q&P treatment were also analysed.