The Effect of a Slow Strain Rate on the Stress Corrosion Resistance of Austenitic Stainless Steel Produced by the Wire Laser Additive Manufacturing Process

Abstract

The wire laser additive manufacturing (WLAM) process is considered a direct-energy deposition method that aims at addressing the need to produce large components having relatively simple geometrics at an affordable cost. This additive manufacturing (AM) process uses wires as raw materials instead of powders and is capable of reaching a deposition rate of up to 3 kg/h, compared with only 0.1 kg/h with common powder bed fusion (PBF) processes. Despite the attractiveness of the WLAM process, there has been only limited research on this technique. In particular, the stress corrosion properties of components produced by this technology have not been the subject of much study. The current study aims at evaluating the effect of a slow strain rate on the stress corrosion resistance of 316L stainless steel produced by the WLAM process in comparison with its counterpart: AISI 316L alloy. Microstructure examination was carried out using optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction analysis, while the mechanical properties were evaluated using tensile strength and hardness measurements. The general corrosion resistance was examined by potentiodynamic polarization and impedance spectroscopy analysis, while the stress corrosion performance was assessed by slow strain rate testing (SSRT) in a 3.5% NaCl solution at ambient temperature. The attained results highlight the inferior mechanical properties, corrosion resistance and stress corrosion performance, especially at a slow strain rate, of the WLAM samples compared with the regular AISI 316L alloy. The differences between the WLAM alloy and AISI 316L alloy were mainly attributed to their dissimilarities in terms of phase compositions, structural morphology and inherent defects.