Microstructure and Corrosion Properties of Wire Arc Additively Manufactured Multi-Trace and Multilayer Stainless Steel 321

Abstract

Because low thermal conductivity and high viscosity are common characteristics of austenitic steel, it is easy to cause a large amount of heat accumulation in the chip area, resulting in tool edge collapse or wear, and the traditional preparation method is unsuitable for preparing large and complex austenitic steel components. Wire + arc additive manufacturing (WAAM) provides a great application value for austenitic stainless steel because it can solve this problem. The cold metal transfer (CMT)-WAAM system with good control of heat input was used to fabricate the multi-trace and multilayer stainless steel 321 (SS 321) workpiece in this study. The microstructure and corrosion properties of the SS 321 workpiece were observed and compared with those of an SS 321 sheet. The results showed that the microstructure of the SS 321 workpiece from top to bottom was regularly and periodically repeated from the overlapping remelting zone, inter-layer remelting zone, and primary melting zone. There was white austenite matrix and black ferrite, and a small amount of skeleton and worm ferrite was distributed on the white austenite matrix. The average hardness value from the top to the bottom region was approximately uniform, indicating that the workpiece had good consistency. The corrosion properties in 0.5 mol/L H2SO4 solutions were compared between the SS 321 workpiece and the SS 321 sheet. The results showed that the corrosion properties of the top region of the workpiece were better than that of the middle and bottom part, and the corrosion properties of the SS 321 workpiece were better than that of the SS 321 sheet.

Corrosion response of steels fabricated through arc directed energy deposition additive manufacturing: a review

“…73 The influence of the location from which samples were extracted on the corrosion behavior of WAAM-fabricated 321 austenitic SS was also investigated in a sulfuric acid solution. 47 The repetitive thermal cycling during WAAM in the middle and bottom sections of WAAM 321 SS facilitated the precipitation of a continuous network of Cr-rich carbides adjacent to the grain boundaries at sensitization temperature. This phenomenon aids in interpreting the observed enhanced corrosion resistance in the top region.…”

“…This phenomenon aids in interpreting the observed enhanced corrosion resistance in the top region. 47 Furthermore, it was observed 47 that the as-printed alloy exhibited superior intergranular corrosion resistance compared to conventional 321 SS sheets. This improvement was attributed to the even dispersion of the ferrite phase within the austenite matrix, which disrupted the continuous network of chromium carbides at the austenite grain boundaries.…”

Microstructure and Corrosion Behavior of AISI 316 Steel Layers Deposited on AISI 347 Steel Substrate by Laser Metal Deposition

“…Therefore, the boundaries outline the austenite cells by etching darker than the interior of the cells owing to the compositional variations caused by microsegregation [14]. A high cooling rate and temperature gradient in the LAM process cause the formation of columnar grains and delta-ferrite [24] The presence of ferrite in the deposit is due to the high cooling rate, which leads to an incomplete delta-ferrite-to-austenite transformation when fully solidified [25,26].…”

Effect of Cl− on Passivation Properties of Fe-20Cr-20Mn-0.75N High Nitrogen Austenitic Stainless Steel

“…In the accelerating corrosion of ASS, there are various mechanisms at play, including the small size, high diffusion rate, and strong acidic anionic properties, leading to the acceleration of the hydrolysis of corrosion products by penetrating the passive film [10,11]. Thus, a localized acidification of the sample, such as pitting, crevice, and stress cracking corrosion, appears in ASS [12][13][14]. Furthermore, Cl − reacts with Fe and/or Cr elements, forming soluble chlorides on the surface of ASS, while also disrupting the formation and stability of the passive film [15,16].…”