Precipitation hardening of nonmagnetic austenitic steels

Investigated was the mechanism of the ageing-induced strengthening of austenitic steels based on 40Kh13N8G8 steel alloyed with molybdenum, niobium or vanadium. Ageing was carried out at temperatures between 600 and 800 deg C for 160 h. It was shown that steels alloyed with strong carbide-forming elements (V, Nb) strengthened considerably during ageing, as the proportion of nondeformed particles (VC, NbC) increased; at holding in excess of 16 h, the strengthening is governed by the interaction between the sliding dislocations and the carbides according to the Orovan mechanism and by the deformation with attendant increase in the density of dislocations. In 40Kh13N8G8 and 40Kh138G8 steels, the strengthening is negligible and is mainly due to the appearance of a carbide network along the boundaries of grains, the network also decreasing plasticity