Evaluation of corrosion properties of TA2-Q345 explosive composite plate at different heat treatment temperatures

This study investigated the effects of post-weld heat treatment (PWHT) at 500 °C, 600 °C, 700 °C, and 800 °C on the microstructure and corrosion performance of the TA2-Q345 explosive composite plate, with TA2 as the flyer plate and Q345 as the base plate. X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) analyses were performed, alongside electrochemical experiments. The explosive welding interface of the TA2-Q345 composite plate exhibited a characteristic wavy structure, which indicated high welding quality. The XRD results indicated that the PWHT temperature significantly affects both the phase structure and the intensity of the diffraction peaks of the oxide film. Additionally, the porosity calculations demonstrated that the sample subjected to PWHT at 500 °C exhibited the lowest porosity in the surface oxide film, resulting in a denser oxide film that effectively enhanced corrosion resistance. However, as the temperature continued to rise, defects such as craters, bulges, and delamination between the oxide film and the titanium matrix were observed. The results of the electrochemical analysis indicated that, compared to untreated samples, the PWHT samples demonstrated improved corrosion resistance. Specifically, the sample with PWHT at 500 °C has the lowest corrosion current density (i_corr) of 6.1892E-06 A/cm², while the untreated sample has the highest i_corr of 6.3577E-05 A/cm², indicating that 500 °C is the optimal temperature. The corrosion process involved the hydrolysis of titanium chloride to form a TiO₂ film and localized corrosion of the TiO₂ protective film. The corrosion products composed of mainly C, O, and Ti were dispersed on the surface of PWHT samples.