High-speed steels with addition of niobium or titanium

Abstract

It was found that about 0.5% Nb or 0.3% Ti may be employed as partial substitutions for vanadium in the W Mo V high-speed steels of the 11-0-2, 11-2-2 and 9-2-2 types, with concentration of Si increased to 0.7%. Additions of niobium or titanium introduced into these steels result in change of the chemical compositions of the MC type primary carbides. This makes possible transition of vanadium, in a sufficient concentration, into the solid solution, and obtaining the secondary hardness effect not lower than in the steels without niobium or titanium, even with lower vanadium concentration in the steel. Additions of the 0.5% Nb or 0.3% Ti secure the highest secondary hardness of about 66 HRC in the investigated steels. The main reason of the secondary hardness effect in the investigated steels with the additions of niobium or titanium is dispersive precipitation of the M 4C 3 carbides in the tempered martensite matrix and the martensitic transformation of the retained austenite.