On Microstructure and Corrosion Properties of Selective Laser Melted 316L Stainless Steel

Abstract

In this study, a laser additive manufacturing method, known as selective laser melting (SLM), was applied to produce cube blocks of 316L stainless steel. The microstructure and corrosion properties of the produced samples were analyzed using scanning electron microscopy, cyclic potentiodynamic polarization testing, and electrochemical impedance spectroscopy. The results were also compared with the properties of a conventional wrought 316L stainless steel sample. The microstructural studies showed that the SLM-manufactured samples have a regular network of melt pools containing austenite grains along with elongated or equiaxed cellular sub-grains. The potentiodynamic polarization results depicted that the SLM fabricated samples had higher positive pitting potential and a wider passivation range than those of the wrought sample, corresponding to their better corrosion resistance. However, the SLM fabricated samples showed a weaker re-passivation property, which possibly is attributed to the presence of preexisting porosities in the structure of the SLM sample formed during the fabrication process. The EIS data also confirmed a larger capacitive arc for the SLM fabricated samples than its wrought counterpart, indicating a higher charge transfer impedance and a better corrosion resistance.

Observations on the influence of process and corrosion related defects on the fatigue strength of 316L stainless steel manufactured by Laser Powder Bed Fusion (L-PBF)

“…Another way to observe more precisely the effect of the defect morphology is to observe defects case by case. Figures 23,24 Figure 23 shows a case where the fatigue strength of the specimens is almost identical (between 275 and 280 MPa) and their critical defects sizes (in terms of √ area) are quite small and close (between 60 and 75 µm). On the other hand, their equivalent circularity, their normalised depth and their Feret ratio are very different from another.…”

“…Some studies highlighted as well the possible role of the fine microstructure resulting from the L-PBF process. Indeed, it could be responsible of an increase in the strength of the passive film, but also, a reduction in pit penetration [2,24,25].…”

Study of the Thermochemical Surface Treatment Effect on the Phase Precipitation and Degradation Behaviour of DSS and SDSS

“…However, the DSS C + TT sample does not present such behaviour. The sharp fluctuations in current density are defined as the metastable pit growth that initiates below the pitting potential, but they cannot propagate for an indefinite period and, therefore, repassivate fairly quickly [44][45][46][47]. In addition, as mentioned before, no pitting potential is reached.…”

Effect of heat treatments on the microstructure and wear behaviour of a selective laser melted maraging steel

“…On the other hand, the Austenite phase is lighter and allows for somewhat more flexibility in MS1 materials. 16,17 As a result, some austenite reversion from martensite can enhance the ductility of maraging steel. 18 The martensite-to-austenite transition is a diffusion-dependent process enhanced when heat-treatment is performed in the intercritical temperature ranges of AC 1 and AC 3 , or even above the AC 3 temperature.…”