Investigation of the Effect of Heat Treatment after Welding on the Corrosion Properties of the Joint of Explosive Bonding of Bronze-Plain Carbon Steel Sheets

In the current research, the microstructural changes and corrosion behavior of two-layer Steel/Bronze sheets were investigated after the heat treatment of the explosive welding process. The heat treatment was performed at 600ºC for 16 hr. Dynamic potential polarization, electrochemical impedance spectroscopy, optical microscopy, and scanning electron microscopy analyses were used. Based on of the electrochemical impedance analysis, the highest polarization resistance, which was equal to 30160 Ω cm2 and followed by the third sample having a resistance of 20720 Ω cm2, was seen in a sample with a stand-off distance of 1.5 mm and an explosive thickness of 20 mm, but the lowest polarization resistance was seen in a sample with a stand-off distance of 2 mm and an explosive thickness of 45 mm. According to the EDS analysis, from a common interface sample with a stand-off distance of 1.5 mm and an explosive thickness of 20 mm, it was concluded that the interface of steel and bronze is noble due to the high concentration of copper in the interface, therefore the corrosion speed is less than other samples. The metallographic results showed a decrease in the amplitude of the waves because of the decreasing the thickness of the explosive charge. Moreover, in the heat treatment samples, the grain size of ferrite grains has a dramatic growth, so, due to recrystallization after the heat treatment, the grains with an elongated appearance are not seen next to the interface.