Samples were cut from AISI H13 steel rods and machined into discs with 18 mm diameter and 5 mm thickness. The samples were ground, austenitized at 1020 °C for 30 min, quenched in oil, tempered for 2 h at 600 °C, metallographically polished, degreased with ether, and then ultrasonically cleaned in acetone for 30 min. The nominal chemical composition of the AISI H13 steel is shown in Table 1.