Evaluation of mechanical properties and corrosion behavior of wire arc additively manufactured 13CR (AISI 420)

Lunde, Jonas Halvorsen (2021) Evaluation of mechanical properties and corrosion behavior of wire arc additively manufactured 13CR (AISI 420). Masters thesis, Memorial University of Newfoundland.

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Abstract

In this study, a 13Cr stainless steel multi-layer thin-wall part was fabricated using wire arc additive manufacturing (WAAM). In Chapter 1 the microstructure and mechanical properties of the bottom, middle and top regions in as-printed condition were investigated. A multi-phase microstructure consisting of a hard martensitic matrix along with retained austenite and delta ferrite was detected for all regions. The top region exhibited both lower strength and elongation compared with the other regions, due to the presence of harder martensite with vermicular delta ferrite. In Chapter 2 a post-fabrication heat treatment was applied to the as-printed part. Here, austenitizing and quenching eliminated the detrimental secondary phases and the microstructure and corrosion behavior after tempering at 300°C, 400°C, 500°C, and 600°C for 2 hours were investigated. Electrochemical tests revealed that tempering at 400°C provided the best corrosion resistance and tempering at 500°C provided the worst resistance. In chapter 3 tempering at 400°C was looked into further by varying the tempering time; 1 h, 2h, 4h, and 8h were investigated by microstructural observations and electrochemical testing. A decreasing corrosion resistance with increasing tempering time was found due to the growth of intergranular carbide precipitates.

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