Effect of Deformation Prior to Nitriding on Microstructure and Hardness Behavior in Plasma-Nitrided Ferritic Alloys

抄録

In order to clarify the effect of deformation prior to nitriding and alloying elements on nitriding behavior in Fe–M binary alloys, pure iron and Fe–M (M = Al, Cr) binary ferritic alloys, which had been deformed by high pressure torsion (HPT) process, were plasma-nitrided at 843 K for 3.6 ks, then the microstructure and hardness of them were investigated. It was found that the effects of deformation on hardness of nitriding diffusion zone in pure iron and Fe–1Cr alloy were small. In contrast, the hardness of diffusion zone in Fe–1Al alloy was greatly increased by deformation because deformation promoted the precipitation of AlN more extensively than non-deformed specimen. In addition, deformation resulted in more homogeneous growth of the compound layer with the finer grain size of γ′ on the compound layer. This feature was observed most remarkably in Fe–1Al alloy, where needle-like γ′ compound layer was formed in the non-deformed specimens.

 

This Paper was Originally Published in Japanese in J. Japan Soc. Heat Treatment 60 (2020) 239–246. The captions of Fig. 5, 7 are slightly modified.

Fig. 7 The α orientation maps and SEM micrographs at 25 um depths from nitriding surface in the regions of γ = 2.6 and γ = 78.5 of (a) Fe–1Al and (b) Fe–1Cr alloys nitrided at 843 K for 3.6 ks.