Effect of Nitrogen on the Carbide in Steel

Abstract

Nitrogen can stabilize the austenite structure, enlarge austenite phase zone, and increase the precipitation temperature of carbides in special steels. In this chapter, the effect of nitrogen on the microstructure, carbide and mechanical properties of high-Mn austenitic die steel is studied. It is found that nitrogen has no effect on the types and morphology of carbides, but changes the composition of carbides. There are more primary precipitates in high-Mn austenitic die steel after adding nitrogen, and the size of primary precipitates increases, which could be related to the increase of precipitation temperature of primary precipitates with nitrogen addition in the steel. After aging treatment, the secondary precipitates in high-Mn austenitic steel with nitrogen addition are only spherical or near spherical V(C, N) with 100–200 nm in size and uniform distribution in the steel, whereas the secondary precipitates are only V8C7, some of which are 0.5–1 μm in size and long strip in morphology, except a small amount of near spherical precipitates of 100–200 nm in size. The secondary precipitates in high-Mn nitrogen-containing austenitic steel are larger in volume fraction and smaller in size in comparison with that in high-Mn austenitic steel without nitrogen addition.