Abstract
This work evaluates microstructural changes and residual stresses on surface samples of AISI 201LN and 304L subjected to shot peening. The residual stresses were measured by X‑ray diffraction and magnetic Barkhausen noise (MBN) in different shot-peened conditions. The results showed that the 201LN steel presented more martensite than the 304L steel in the initial condition, but with lower δ‑ferrite contents. These ferromagnetic phases were present in a low amount with high tensile residual stresses due to brush cleaning and light cold‑rolling in the final stage of the fabrication process. The shot peening process promoted compressive residual stresses mainly in the δ‑ferrite. However, some “fresh” martensite exhibited tensile residual stress represented by higher and thinner peaks, which together with the low-intensity amplitude in the neighborhood, represented all formed martensite. Thus, small microstructural changes provoked high residual stresses behavior, which can be detected in ferromagnetic phases by MBN.
Highlights
Austenitic stainless steels (ASS) have good mechanical properties and corrosion resistance, and for this reason are used in various industrial sectors, such as equipment for food, pharmaceutical, nuclear, aerospace and petroleum industries[1,2]
The dark phase indicated by white arrows represents the elongated delta ferrite, which was verified in the rolling direction (RD)[31,32]
According to ASTM E11221, the average grain size determined through the intercept method using ImageJ33 was 18±4 μm for 201LN steel and 25±5 μm for 304L steel
Summary
Austenitic stainless steels (ASS) have good mechanical properties and corrosion resistance, and for this reason are used in various industrial sectors, such as equipment for food, pharmaceutical, nuclear, aerospace and petroleum industries[1,2]. In this family of austenitic stainless steels, the 300 series is the most commonly used and is characterized by a high content of chromium and nickel. In some stainless steel designations, the austenite phase is more metastable and promotes austenite transformation into martensite, achieving the desired mechanical properties, mainly due to the chemical composition In this way, stacking fault energy (SFE) plays a major role in martensitic transformation, but grain size, degree of deformation and temperature contribute to this mechanism[5]
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