Laser shock peening (LSP) without ablative coating at various power densities was applied to AA6082 aluminium alloy to investigate corrosion behaviour in a 0.6 M NaCl solution. Cyclic polarisation results showed enhanced passivity with corrosion current reduction by as much as a factor of 12, compared to the untreated specimen. Additionally, EIS after 24 h confirmed almost seven times higher polarisation resistance after LSP, compared to the untreated specimen (45 and 6.7 k cm2). XPS analysis indicated Al2O3 enrichment, which contributed to higher corrosion resistance with reduced anodic dissolution of the LSP-treated surface due to plasma ablation and shock waves.
F.02 Acquisition of new scientific knowledge
COBISS.SI-ID: 12293915The influence of nanosecond laser pulses applied by laser shock peening without absorbent coating (LSPwC) with a Q-switched Nd:YAG laser operating at a wavelength of λ=1064 nm on 6082-T651 Al alloy has been investigated. The first portion of the present study assesses laser shock peening effect at two pulse densities on three-dimensional (3D) surface topography characteristics. In the second part of the study, the peening effect on surface texture orientation and micro-structure modification, i.e. the effect of surface craters due to plasma and shock waves, were investigated in both longitudinal (L) and transverse (T) directions of the laser-beam movement. In the final portion of the study, the changes of mechanical properties were evaluated with a residual stress profile and Vickers micro-hardness through depth variation in the near surface layer, whereas factorial design with a response surface methodology (RSM) was applied. The surface topographic and micro-structural effect of laser shock peening were characterised with optical microscopy, Infinite-Focus® microscopy and scanning electron microscopy (SEM). Residual stress evaluation based on a hole-drilling integral method confirmed higher compression at the near surface layer (33 μm) in the transverse direction ( min) of laser-beam movement, i.e. -407 ± 81 MPa and -346 ± 124 MPa, after 900 and 2500 pulses/cm², respectively. Moreover, RSM analysis of micro-hardness through depth distribution confirmed an increase at both pulse densities, whereas LSPwC-generated shock waves showed the impact effect of up to 800 μm below the surface. Furthermore, ANOVA results confirmed the insignificant influence of LSPwC treatment direction on micro-hardness distribution indicating essentially homogeneous conditions, in both L and T directions.
F.02 Acquisition of new scientific knowledge
COBISS.SI-ID: 12438043