Effect of nitrogen on the austenite cooling transformation kinetics of a high-speed steel

The austenite cooling transformation kinetics of a semi-high-speed steel (HSS) with or without additional nitrogen was studied by means of DT1000 dilatometer. The stability and composition of the carbides have also been investigated using transmission electron microscopy and scanning electron microscopy. The results indicate that the addition of nitrogen can improve the hardening ability and bring down the Ms temperature of the steel. The carbides in the semi-HSS with nitrogen addition contain more W and Mo elements and less Cr element. They exhibit higher stability. Quenching hardness of the semi-HSS with N is insensitive to the austenization temperature in the range from 1223 to 1423 K.