Ultrasonic studies of texture inhomogeneities in pressure vessel steel subjected to ultrasonic impact treatment and shock compression

- Texture formation at ultrasonic impact treatment (UIT) of pressure vessel steel is studied.
- Precise measurements of the bulk-wave ultrasonic velocities and specimen densities are used.
- Quantitative analysis of the crystallographic texture is made in various layers of the deformed specimens.
- Texture registered by ultrasonic method used and X-ray analysis correlates with microhardness and strain extent distributions.
- Texture is formed in the subsurface layers of the material processed with UIT.

Specimens of Cr-Ni-Mo-V pressure vessel steel 15Kh2NМFА were cut from the achieve wall of the WWER-1000 reactor and were then deformed either using ultrasonic impact treatment (UIT) inducing low energy multiple impacts or by drop-hammer inducing high energy shock compression (HESC). With the aim of texture evaluation comprehensive ultrasonic measurements and X-ray texture analysis were carried out in different sections of the deformed specimens. A nondestructive quantitative analysis of the crystallographic texture in various layers of the deformed specimens was performed on the base of precise measurements of the bulk-wave ultrasonic velocities (vij) by means of the pulse-echo method using a home-made automated apparatus. The mass densities (ρ) of the deformed specimens and their cut sections were also precisely measured. The obtained data allowed calculating orientation distribution coefficients (W4i0) of crystallites and to construct ultrasonic pole figures for different specimen layers and cut sections. The ultrasonic pole figures correlate well to the X-ray pole figures registered in the cut sections of the specimens. It is found that maximal pole intensities (ΔI[ijk]) and spatial inhomogeneities of these textures depend on the used regimes of UIT and HESC. The revealed peculiarities of the texture formation correlate well to the depth distributions of microhardness and strain extents. The higher the strain extent or the longer the treatment time, the more intensive texture is registered and the deeper the textured layer is observed. The ultrasonic method applied is shown to be useful and efficient for non-destructive examination of elastically heterogeneous systems, particularly the materials with mechanically treated surfaces.

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