Positron Annihilation Study of Defects Induced by Various Cutting Methods in Stainless Steel Grade 304

We report in this article the comparison of the subsurface zones (SZs) in austenitic stainless steel 304 samples created by three cutting techniques, i.e., the laser cutting (LC), abrasive water jet (AWJ), and traditional milling cutting (MC). The crystal lattice defects distribution in this zone were investigated using the positron annihilation method. It was shown that the MC creates the great number mainly edge dislocations decorated by vacancies. Their concentration decreases with the increase of the depth from the cut surface. The total depth of the SZ is extended up to 150 μm from the cut surface. Similar dependency was observed for the AWJ machining but the total depth is much lower, i.e., 40 μm. The laser cut machining generates the zone with the lowest concentration of defects which does not vary with the depth. However, LC affects the sample up to the depth of about 500 μm. The degree of the surface roughness is similar for laser cut and AWJ, but for the MC it is five times smaller.

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