Comparative Study of 9% Cr Martensitic-ferritic Steels Using Differential Scanning Calorimetry

In this paper we study comparatively the transformation behavior of three 9% Cr alloys by using the Differential Scanning Calorimetry (DSC) technique, with thermal cycles including heating, austenite holding and cooling at rates between 1.5 and 50 °C/min. The starting metallurgical state corresponds to the as-received -that is, normalized and tempered- material. Transformation critical temperatures are determined in each case and, in particular, the dependence of those temperatures with respect to the cooling rate is examined. At the same time, approximate bounds of the critical cooling rate for martensite formation are given and compared between the different alloys. Finally, DSC results are evaluated as compared to literature values and to previous results of our laboratory obtained by the dilatometry technique.