## 5 Conclusions  
In this paper, we investigate the low-temperature ion nitriding surface strengthening process of AISI 316L austenitic stainless steel, which shows promising application prospects. We employ a dual strategy of deformation treatment and low-temperature nitriding to explore the effects of defect density, grain boundary density, and changes in the second phase on the nitriding effectiveness of 316L stainless steel which has been subjected to various deformation variables. Additionally, we examine the related impact on hardness. The results are summarized as follows:  
1. The deformation of 316L stainless steel at room temperature results in the formation of a significant number of dislocations, lamellae, martensite, and other microstructures. At a deformation level of 10%, the microstructural changes within the 316L stainless steel matrix are predominantly characterized by the presence of martensite and twin structures. As the deformation increases to 30% or more, the material exhibits a considerable number of structural defects within its microstructure.  
2. Under identical nitriding temperatures, as the amount of deformation increases, the content of deformation-induced martensite in 316L stainless steel also increases. The formation of deformation-induced martensite is associated with the generation of dislocations and other structural defects, which hinder the migration of dislocations. This phenomenon  
Figure 9: Nitrogen EDS change (The direction of the arrow is the direction of the line scan) of 316L stainless steel plasma-nitrided layer under different deformations (**a**) 0; (**b**) 10%; (**c**) 20%; (**d**) 30%; (**e**) 40%; (**f**) 50%.  
enhances the strength of the intergranular deformation structure and contributes to an improvement in surface hardness.  
3. The deformation treatment of 316L results in the formation of dislocations, laminar faults, grain boundaries, martensite, and other microstructural features. These structures, along with the interaction between dislocations and nitrogen atoms, facilitate the spread of nitrogen atoms. Consequently, this process enhances the growth of the penetration layer thickness during the low-temperature nitriding of 316L stainless steel and improves the hardness of this layer. However, this process concurrently leads to a reduction in the corrosion resistance of the permeate layer. One can observe that the thickness of the penetration layer increases with morphological changes and, similarly, the hardness of the penetration layer also increases with the enhancement of morphology. Conversely, the corrosion resistance of the nitrided layer diminishes with an increase in morphology.  
Conceptualization, K.S.; data curation, X.Z. and L.Z.; formal analysis, X.Z. and C.M.; investigation, X.Z., L.Z., C.M., and K.S.; methodology, X.H.; writing--original draft, X.Z.; writing--review and editing, X.Z., L.Z., C.M., X.H., and K.S. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
Date are contained within the article.  
The authors declare no conflicts of interest.  
The following abbreviations are used in this manuscript:  
\begin{tabular}{l l} SEM & Scanning electron microscope \\ EBSD & Electron backscatter diffraction \\ EDS & Energy-dispersive X-ray spectroscopy \\ XRD & X-ray diffraction \\ BCC & Body-centered cubic \\ BCT & Body-centered tetragonal \\ FCC & Face-centered cubic \\ KAM & Kernel Average Misorientation \\ \end{tabular}