Experimental and numerical studies on the electrochemical properties of an electrically assisted pressure joint of austenitic stainless steel and Ni-based superalloy

Electrochemical properties of an austenitic stainless steel and Ni-based superalloy dissimilar joint, produced by electrically assisted pressure joining (EAPJ), are investigated and compared to the base metals in a 3.5% NaCl solution at room temperature. The microstructural analysis reveals a sound joint without the presence of secondary phases and/or low melting phases (Laves) in the EAPJ joint due to the short diffusion time and rapid local heating. However, the microstructure of the joint is characterized by some degree of grain refinement, high dislocation densities, and a decrease in major passive-forming elements across the joint interface. These microstructural changes cause an increase in the risk of galvanic corrosion across the joint, with the SUS316L side undergoing severe localized corrosion attacks. Furthermore, a numerical model is established using the corrosion parameters from the experiment to simulate the electrochemical behavior of the joint in a neutral environment. The simulation results agree reasonably well with the experimental results in relation to the corrosion potentials, current densities, and the corresponding corrosion rates. Also, the model is capable of tracking the dissolution of the SUS316L side of the joint during the corrosion process for any period.