PSI - Issue 68

Tsanka Dikova et al. / Procedia Structural Integrity 68 (2025) 99–105 Tsanka Dikova & Natalina Panova / Structural Integrity Procedia 00 (2025) 000–000

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The development of corrosion in depth of untreated AISI 321 steel, tested in Ringer’s solution, is shown in Fig. 3. It can be clearly seen that the corrosion destruction starts from the surface and runs in depth selectively, mainly through the δ-ferrite grains, in the form of pits of irregular shape and great depth (50-300 µm). Intergranular corrosion is also observed along the austenite grain boundaries near the surface (shown with arrows in Fig. 3a). The corrosion development in depth of laser melted layers also runs selectively by δ-ferrite destruction in the form of shallow (40 100 µm) equiaxed pits (Fig. 4). The same destruction type is observed in the laser melted layer as well as at the Fig. 2. SEM images of corrosion damage on the surface of AISI 321 steel in artificial saliva with pH 5.6. (a), (b) Untreated surface of sample 0; Surfaces of laser melted layers of (c), (d) sample 1; (e), (f) sample 4; (g), (h) sample 6.

Fig. 4. Development of corrosion destruction in depth of laser melted layer of AISI

Fig. 3. Corrosion destruction in depth of

image (A-austenite, δF–δ ferrite).