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.

This work studies the application of a Non-Destructive Inspection Technique (NDIT), based on the Magnetic Barkhausen Noise (MBN), for the detection of non-homogeneous regions in carbon steel plates. It presents the advances in the development of a variant of a new non-destructive magnetic test technique, called Continuous Scanning Magnetic Barkhausen Noise (CSMBN). The non-homogeneous or damaged regions were produced by plastic deformations in rolled and annealed sheets of SAE 1060 and 1070 steels. MBN is generated by abrupt changes in the magnetization of materials when subjected to alteration. The sensitivity of the MBN signals in the detection of plastic deformations was analyzed varying parameters such as excitation magnetic field frequency and the speed of movement of the probe. The behavior of the root mean square of magnetic Barkhausen Noise signal (RMSMBN) parameter was correlated with the position of the nonhomogeneous regions detected in the samples. An evaluation of the technique applied to the measurement was made, comparing the results obtained with the Static Magnetic Barkhausen Noise (SMBN) technique, which is a method already established in the literature. The results showed that in all cases studied it was possible to detect the position of the damage, due to variation of the magnetic field. These changes are affected by the presence and distribution of elastic stresses (compression and traction), plastic deformation and microstructure modification. The results of CSMBN were similar to the SBMN with the advantage of being a continuous and more productive procedure. This new technique increases the spectrum of NDIT solutions for problems not contemplated by existing techniques.