Influence of mechanical processing and heat treatment on microstructure evolution in nickel free high nitrogen austenitic stainless steels

A series of nickel free high nitrogen austenitic stainless steels were proc essed by various mechanical processing and heat treatment conditions to stu dy the evolution of microstructure at every stage of processing. About elev en steels varying in composition, especially in terms of carbon contents, w ere processed through forging, rolling, solution annealing, cold rolling an d warm rolling etc. The microstructure at every stage of processing was stu died. The hot relied condition, hot rolled and cold rolled condition gave d eformation induced fragmented grain structure. The high carbon steels in th e hot rolled conditions showed banding and grain boundary carbo-nitride pre cipitation. There were also intragranular carbide prcipitation in some of t he high carbon steels. The solution treated microstructure in all steels sh owed extensive annealing twins and the lattice parameter increased with car bon and nitrogen contents. Cold rolling followed by solution treatment lead to development of slip lines in the fully austenitic matrix due to strain hardening of the matrix. The 600 degrees C warm rolled condition showed gra in boundary carbide precipitation.