Effects of Quench and partitioning Heat Treatment in mechanical properties and the microstructural characterization of AISI 300M Steel

The present work explored thermal processing routes of quenching followed by partitioning to obtain a multiphase microstructure combining brittle and ductile elements with excellent mechanical properties. According to each planned route, this work shows the effects in the mechanical behavior and multiphase microstructural analysis from the low alloyed high strength steel AISI 300M, aeronautical grade. The mechanical characterization was performed through traction tests, for determining strength and ductility values. It were also anaysed the toughness values through Charpy “V” impact strength testing, besides the hardness, measured in Rockwell “C” scale. For the microstructural characterization, the samples were prepared with several metallographic etchants (Nital 2%, LePera, Aqueous solution of 10% sodium metabisulfite) and with the help of an optical microscope it were determined the microconstituents present, such as martensite and stabilized retained austenite. Through the thermal processing routes of quench and partitioning, it was possible to reach interesting mechanical properties and microstructural features combining high mechanical strength with increased toughness. The test results of the mechanical and microstructural behavior were discussed and confronted according to the proposed thermal processing situation. This work was supported by the academic institutions EESC – USP and IFSP Brazil, as well as by the company Durferrit from the HEF group.