Prediction of KIc in a high strength bainitic steel

•Specimens to fracture mechanics tests were machined according to ASTM E 399 standard.•The expression given by Lescovsek acceptably predicts the value of KIc.•The value of CVN has more of an influence on KIc than HRc.•Reducing the bainitic packet size the KIc is increased.

In this work the stress intensity factor (KIc) has been determined for a high strength bainitic steel, making reference to ASTM E 399 standard, which involves the use of complex geometry specimens. An experimental value of 1627 N mm−3/2 has been obtained for KIc, which is equivalent to 51.4 MPa m1/2. It has been verified that Lescovsek’s expression, which predicts KIc as a function of hardness (HRc) and the CVN Charpy impact test value, can be applied to steels with a bainitic microstructure, as the CVN value is more influential than HRc. The acceptable prediction of Lescovsek’s expression shows the way to improve the KIc value in bainitic steels.