Effects of microstructural evolution on the corrosion properties of AISI 420 martensitic stainless steel during cold rolling process

Effects of Secondary-Phase Formation on the Electrochemical Performance of a Wire Arc Additive Manufactured 420 Martensitic Stainless Steel under Different Heat Treatment Conditions

“…Figure 8 shows the obtained Nyquist diagrams for the as-printed and heat-treated samples, after 1 and 120 h of immersion times. Nyquist diagrams of all samples exhibited one broad capacitive semicircle, as a result of the superposition of two individual peaks with neutral time constants for both immersion times (Ref 15 ). The significantly larger semicircle curves in the Nyquist diagrams for the Q&T sample at both immersion times as compared to the other two samples confirm the more protective nature of the passive film formed on the Q&T sample (Ref 15 ), consistent with the observed trend in the PDP results.…”

“…Nyquist diagrams of all samples exhibited one broad capacitive semicircle, as a result of the superposition of two individual peaks with neutral time constants for both immersion times (Ref 15 ). The significantly larger semicircle curves in the Nyquist diagrams for the Q&T sample at both immersion times as compared to the other two samples confirm the more protective nature of the passive film formed on the Q&T sample (Ref 15 ), consistent with the observed trend in the PDP results. After the longer immersion time of 120 h, a significant reduction in the radius of the Nyquist curves was detected, ascribed to the continuous dissolution of the passive layer into the solution over time, causing severe deterioration in the electrochemical stability (Ref 15 ).…”

“…In this model (Ref 19 ), the C eff is described as: , where ε is the passive film dielectric constant (~15.6 for Cr 2 O 3 ), ε 0 is the vacuum permittivity (8.854 ×10 −14 F cm −1 ) (Ref 20 ), g is a function of n ( ), and is the passive layer resistance at its maximum thickness. The passive layer thickness in steady-state condition ( L ss ) can be estimated based on the EIS data and using the plate capacitor relationship as suggested in (Ref 15 , 21 ): , where A is the is the surface area of the corroded sample. The calculated L ss and C eff values for the samples, presented in Table 5 , confirmed a higher passive layer thickness for the Q&T sample, while it decreases for the other samples in the order of annealed sample > as-printed sample, consistent with the OCP, PDP, and EIS results.…”

“…Most commercial sheets of MSSs are available in the soft annealed condition with islands of spherical carbides embedded in a ferritic matrix, possessing high ductility and relatively lower strength, leading to their outstanding formability (Ref 3 ). MSSs can also be heat treated through a quenching and tempering (Q&T) cycle, in which newly-precipitated carbides form in a martensitic matrix, resulting in a higher hardness and strength (Ref 4 , 5 ). Among all MSSs, 420 MSS with 13 wt.% chromium is commonly used for plastic molding applications, where sufficient corrosion and wear resistance is required (Ref 6 ).…”

“…Hence, developing a systematic post-printing heat treatment cycle is required to eliminate the formation of unfavorable micro-constituents and enhance the mechanical and corrosion performance of the WAAM part. Furthermore, the variation of crystallographic orientation (texture) during post-printing heat treatment can also contribute to the overall corrosion resistance of the alloy either by formation of a preferential texture during the heat treatment process or altering the misorientation nature of grain boundaries (Ref 4 , 15 ). Therefore, this study aims to characterize the effect of different post-printing heat treatments, i.e., annealing and quenching and tempering, on the corrosion performance of a WAAM fabricated 420 MSS with respect to the micro-constituents’ evolution and texture annihilation during heat treatment.…”