ABSTRACT

Additive manufacturing is a method to manufacture 3D shape of resin or metal. Searching proper manufacturing condition and evaluating mechanical property and microstructure of Titanium-base, Cobalt-base, Nickel-base alloys and stainless steel for the fields such as aerospace, medical and defense field have been progressed. However, there are not many reports about corrosion and oxidation resistance of these alloys especially, there are a few reports about their corrosion resistance in acidic solutions. In this study, high and low porosity specimens of additively manufactured (AM) alloys of UNS+ N06210 and UNS S31603 were prepared intendedly with the selective laser melting (SLM) method. The high and low porosity specimens of AM N06210 and AM S31603 were immersed in several kinds of acidic solutions to estimate their corrosion rate and understand the dependency of the corrosion properties of those on porosity. The paper reveals that corrosion rates of low porosity AM S31603 and AM N06210 in several kinds of acidic solutions were similar to those of wrought alloys respectively, the corrosion rates of AM S31603 and AM N06210 became higher with increasing porosity of each specimen.

INTRODUCTION

Additive manufacturing (AM) is a method to manufacture 3D shape of resin or metals. Metal AM was developed by University of Texas in Austin in the 1980s1, and it has been developed in several countries. Searching proper manufacturing condition and evaluating mechanical property and microstructure of Titanium-base, Cobalt-base, Nickel-base alloys and stainless steel for the fields such as aerospace, medical and defense field have been progressed2-8. However, there are not many reports about corrosion and oxidation resistance of these alloys and especially, there are a few reports about corrosion resistance of them in acidic solutions9-14. Hamu reported corrosion behavior of AM and wrought alloy R56400 specimens with ASTM G5 method10. The paper showed that corrosion property of AM specimens depended on building direction of AM and surface conditions and a wrought R56400 exhibited a higher corrosion rate in comparison to the cross sectional condition of the AM specimens. Klapper reported corrosion properties of age-hardened AM alloy N07718 in deaerated 13wt% NaCl at 80°C and in aerated 21wt% NaCl + 0.1N HCl at 90°C with electrochemical technique11. The paper showed that the electrochemical behavior of AM N07718 material as-built surface was independent of the building orientation. Cao et. al reported corrosion property of AM alloy S17400, N06625 and R56400 with electrochemical technique12. The paper reported that every AM materials showed comparable corrosion behavior with its wrought counterpart in several kinds of solutions. Sander et. al. reported that corrosion property of AM S31603 that have several kinds of porosities under 0.4% with electrochemical technique14. The paper reported that AM S31603 showed more resistant to pitting initiation than wrought S31603 and the Ecorr, icorr and Epit values of the AM specimens didn't vary significantly with the porosities of AM specimens.

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