We tested the three 15N20 samples and got somewhat disappointing results. We got values of 8.9, 9.0, and 23.8 ft-lbs. So we got two low values and one much higher value, meaning it is difficult to conclude much from the tests. None of those values are anywhere close to the toughness measured for AEB-L. The results might be inconsistent due to their prior use as saw blades, but we're not really sure.
The heat treatment was: subcritical anneal at 1175°F, austenitize at 1475°F, quench in Parks #50, liquid nitrogen for 20 minutes, temper 2x at 375°F for final hardness of 60 Rc.