Effect of an absorbent overlay on the residual stress field induced by laser shock processing on aluminum samples

• Published in: Applied surface science 2006-07, Vol.252 (18), p.6201-6205
• Main Authors: Rubio-González, C., Gomez-Rosas, G., Ocaña, J.L., Molpeceres, C., Banderas, A., Porro, J., Morales, M.
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; High-pressure and shock-wave effects in solids and liquids; Laser shock processing; Materials science; Mechanical and acoustical properties of condensed matter; Physics; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; Plasma production and heating; Plasma production and heating by laser beams; Residual stress; Surface treatments
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2005.08.062

Laser shock processing (LSP) or laser shock peening is a new technique for strengthening metals. This process induces a compressive residual stress field, which increases fatigue crack initiation life and reduces fatigue crack growth rate. Specimens of 6061-T6 aluminum alloy are used in this investigation. A convergent lens is used to deliver 2.5 J, 8 ns laser pulses by a Q-switch Nd:YAG laser, operating at 10 Hz. The pulses are focused to a diameter of 1.5 mm onto aluminum samples. Density of 2500 pulses/cm 2 with infrared (1064 nm) radiation was used. The effect of an absorbent overlay on the residual stress field using this LSP setup and this energy level is evaluated. Residual stress distribution as a function of depth is assessed by the hole drilling method. It is observed that the overlay makes the compressive residual stress profile move to the surface. This effect is explained on the basis of the vaporization of the coat layer suppressing thermal effects on the metallic substrate. The effect of coating the specimen surface before LSP treatment may have advantages on improving wear and contact fatigue properties of this aluminum alloy.