The evolution of carbides in the tempering process of semi-high speed steel cold rolls with nitrogen addition

摘要

This study analyzes the evolution of carbides in the tempering process of a newly developed semi-high speed steel cold forged roll with nitrogen addition using a transmission electron microscope (TEM) equipped with an energy dispersive X-ray (EDX).The precipitation sequence of the carbides was identified in the entire tempering process and it can be expressed as M3C→M3C+M(C,N)Ⅱ→M(C,N)Ⅱ+ M7C3Ⅱ+M23C6.The secondary hardening in the tempering process was mainly due to the dispersed precipitation of fine M(C,N)Ⅱ particles.The dissolution of M3C tempered at high temperatures induced the precipitation and coarsening of M7C3Ⅱ and M23C6.