Study of the Mechanical Properties of a Nanostructured Surface Layer on 316L Stainless Steel

Abstract

A nanostructured surface layer (NSSL) was generated on a 316L stainless steel plate through surface nanocrystallization (SNC). The grains of the surface layer were refined to nanoscale after SNC treatment. Moreover, the microstructure and mechanical properties of NSSL were analyzed with a transmission electron microscope (TEM) and scanning electron microscope (SEM), through nanoindentation, and through reverse analysis of finite element method (FEM). TEM results showed that the grains in the NSSL measured 8 nm. In addition, these nanocrystalline grains took the form of random crystallographic orientation and were roughly equiaxed in shape. In situ SEM observations of the tensile process confirmed that the motions of the dislocations were determined from within the material and that the motions were blocked by the NSSL, thus improving overall yielding stress. Meanwhile, the nanohardness and the elastic modulus of the NSSL, as well as those of the matrix, were obtained with nanoindentation technology. The reverse analysis of FEM was conducted with MARC software, and the process of nanoindentation on the NSSL and the matrix was simulated. The plastic mechanical properties of NSSL can be derived from the simulation by comparing the results of the simulation and of actual nanoindentation.

Structural and Micromechanical Properties of Nd:YAG Laser Marking Stainless Steel (AISI 304 and AISI 316)

“…The average values of reduced modulus determined for the irradiation depth ranging from 1000-2500 nm are summarized in Table 2. These results are significantly influenced with respect to the substrate effect, and are in accordance with those reported in [51][52][53]. These results revealed the heterogeneity of elastics properties, which are strongly influenced by hard oxide formation caused by laser irradiation.…”

“…This value is slightly higher than the bulk hardness of untreated stainless steel (around 2.2 GPa), and can be treated as the maximum average hardness influenced highly by untreated substrate. The measured base hardness for AISI 304 and AISI 316 stainless seems to be in accordance with the study performed by Chang Ye et al [50], and with those conducted by Lang et al [51]. Based on indentation hardness profiles, the evaluated thickness of laser proceeded layers reached a maximum of 1000 nm, depending on the modification process parameters.…”

Developing a nanostructured surface layer on AISI 316 stainless steel by ultrasonic surface nanocrystallization and evaluating its tribological properties

“…Since the development of the surface layers of materials to nanocrystalline structure prevent the beginning and the propagation of cracks, surface nanocrystallization would be expected to enhance the service life of the materials. Hence, surface modification techniques by creating a nanocrystalline surface layer have been applied as an efficient procedure to improve the overall behavior of materials [6][7][8][9].…”