Corrosion behavior of laser powder bed fusion TA2-Cu-Q345 composite plate subjected to picosecond laser shock peening

Abstract

In this study, the corrosion behavior of laser powder bed fusion (LPBF) TA2-Cu-Q345 composite plate treated by picosecond laser shock processing (PsLSP) at 85 μJ, 145 μJ, and 200 μJ was evaluated. The corrosion mechanism was analyzed through experiments assessing surface roughness, microhardness, residual stress, phase structure, wettability and electrochemical test. The surface roughness, microhardness and residual stress of PsLSPed samples increases with the rising laser pulse energy. At 200 μJ, the microhardness and residual stress on the sample surface were 252.5 ± 30 HV and −196.5 ± 13.6 MPa, respectively. The corrosion current density (i_corr) of the PsLSPed sample was significantly reduced, with the 200 μJ PsLSPed sample exhibiting the lowest i_corr of 1.05E−06 A/cm². The corrosion morphology of PsLSPed samples showed fewer defects than that of untreated sample, which is attributed to the metal hardening layer on the surface that limits the further penetration of chloride ions into the TA2 matrix. Moreover, the high-hardness metal layer on the surface of PsLSPed samples effectively prevents crack formation. The primary reasons for the improved corrosion resistance were likely related to the hardening layer, residual stress, and TiO₂ oxide layer formed on the surface by PsLSP treatment, while surface roughness and hydrophilicity had minimal effects on corrosion resistance.