Influence of Temperature and Time of Austempering Treatment on Mechanical Properties of SAE 9254 Commercial Steel

This work describes the steps in the study and development of the high content of C, Si, and Cr in commercial steel with a nanostructured matrix of martensite, bainite and retained austenite. Specimens of this steel were austenitized at 900 °C for 5 min and isothermally heat treated at different times (0.5, 2, 24, 48 h) and temperatures (200, 220, 270  °C). Different mechanical behavior was observed for the samples treated under different conditions due to their microstructural constitution. Specimens treated for 2 h at 200 °C showed lower yield strength of 979 MPa. On the other hand a high tensile strength of 2248 MPa was reached. The sample treated at 270 °C showed higher yield strength of 1363 MPa with the same treatment time. As for the fracture analysis, the brittle fracture mechanism was predominant for the samples treated at 200 °C, while the ductile fracture mechanism was predominant for the samples treated at 270 °C.