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. 2022 Jun 1;15(11):3947.
doi: 10.3390/ma15113947.

Effect of Laser Peening on Microstructural Changes in GTA-Welded 304L Stainless Steel

Young-Ran Yoo  1 , Jae-Sung Kim  2 , Young-Sik Kim  1   3
Affiliations

Effect of Laser Peening on Microstructural Changes in GTA-Welded 304L Stainless Steel

Young-Ran Yoo et al. Materials (Basel). .

Abstract

The introduction of tensile residual stress has led to the induction of damage such as fatigue, corrosion fatigue, and stress corrosion cracking (SCC) in stainless steel in association with the influence of environments, components, surface defects, and corrosive factors during its use. Compressive residual stress can be achieved through various techniques. Among several methods, laser peening can be more attractive as it creates regularity on the surface with a high-quality surface finish. However, there is very little research on heavily peened surface and cross-section of stainless steel with very deep compressive residual stress. This work focused on welding and laser peening and the influence of Al coating on the microstructural changes in 304L stainless steel. The specimen obtained by laser peening had a very deep compressive residual stress of over 1 mm and was evaluated based on microstructural and hardness analysis. Therefore, a model for microstructural change by laser peening on welded 304L stainless steel was proposed.

Keywords: hardness; laser peening; microstructure; stainless steel; welding.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Schematic diagram of the base metal, HAZ, and welded metal specimens.
Figure 2
Figure 2
Schematic of laser peening process.
Figure 3
Figure 3
Optical microstructure of 304L stainless steel before LP (OM, ×200, 10% oxalic acid); (a) 304LB (base metal), (b) 304LW-H (HAZ), and (c) 304LW-W (weldment).
Figure 4
Figure 4
The surface appearance of 304L stainless steel after LP; (a) 304L(nonpeened), (b) 304L-L-NC (laser-peened without Al coating), and (c) 304L-L-WC (laser-peened with Al coating).
Figure 5
Figure 5
SEM images and elemental distribution on the surface of 304L stainless steel after LP: (a) 304L, (b) 304L-L-NC, and (c) 304L-L-WC.
Figure 5
Figure 5
SEM images and elemental distribution on the surface of 304L stainless steel after LP: (a) 304L, (b) 304L-L-NC, and (c) 304L-L-WC.
Figure 6
Figure 6
The X-ray diffraction patterns of 304L stainless steel after LP: (a) base metal, (b) weldment.
Figure 7
Figure 7
Optical microstructure of the cross-section of 304L base metal after LP (OM, ×200, 10% oxalic acid): (a) 304LB, (b) 304LB-L-NC, and (c) 304LB-L-WC.
Figure 8
Figure 8
Optical microstructure of the cross-section of 304L HAZ area after LP (OM, ×200, 10% oxalic acid): (a) 304LB, (b) 304LB-L-NC, and (c) 304LB-L-WC.
Figure 9
Figure 9
Optical microstructure of the cross-section of 304L weldment area after laser peening (OM, ×200, 10% oxalic acid): (a) 304LB, (b) 304LB-L-NC, and (c) 304LB-L-WC.
Figure 10
Figure 10
EBSD results of 304L base metal after laser peening (EBSD: step size 0.3 μm, depth ~150 μm): (a) IPF coloring, (b) band contrast, (c) recrystallized fraction, and (d) dislocation density.
Figure 11
Figure 11
EBSD results of 304L HAZ area after laser peening (EBSD: step size 0.3 μm, depth ~150 μm): (a) IPF coloring, (b) band contrast, (c) recrystallized fraction, and (d) dislocation density.
Figure 12
Figure 12
EBSD results of 304L weldment after laser peening (EBSD: step size 0.3 μm, depth ~150 μm); (a) IPF coloring, (b) band contrast, (c) recrystallized fraction, and (d) dislocation density.
Figure 13
Figure 13
The hardness of the cross-section of 304L stainless steel after LP: (a) base metal, (b) HAZ, and (c) weldment.
Figure 14
Figure 14
Proposed model of the microstructural variation in 304L stainless steel by (a) welding and (b) laser peening.
See this image and copyright information in PMC

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