Unexpected Interface Corrosion and Sensitization Susceptibility in Additively Manufactured Austenitic Stainless Steel

This communication describes observations of unexpected microstructural interface susceptibility to accelerated dissolution in additively manufactured (AM) Type 316L stainless steel prepared by selective laser melting. Observations include accelerated microstructural interface dissolution in the as-...

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Bibliographic Details
Published inCorrosion (Houston, Tex.) Vol. 74; no. 2; pp. 153 - 157
Main Authors Macatangay, D.A., Thomas, S., Birbilis, N., Kelly, R.G.
Format Journal Article
LanguageEnglish
Published Houston NACE International 01.02.2018
Subjects
Additive manufacturing
Annealing
Austenitic stainless steels
Boundaries
Communication
Corrosion
Dissolution
Dissolving
Electrolytic etching
Etching
Exposure
Grain boundaries
High temperature
Interfaces
Interferometry
Laser beam melting
Lasers
Light microscopy
Melt pools
Optical microscopy
Scanning electron microscopy
Stainless steel
Susceptibility
Temperature
Titanium alloys
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Summary:This communication describes observations of unexpected microstructural interface susceptibility to accelerated dissolution in additively manufactured (AM) Type 316L stainless steel prepared by selective laser melting. Observations include accelerated microstructural interface dissolution in the as-built condition, as well as more rapid sensitization of grain boundaries upon exposure to elevated temperature. Electrolytic etching in persulfate solution was used to evaluate the susceptibility of microstructural interfaces to accelerated dissolution in both wrought and AM 316L. Post-test optical microscopy and profilometry on AM 316L revealed that the melt pool boundaries in the as-built condition were susceptible to accelerated attack, although the small grains within the prior melt pools were not. Furthermore, short, elevated temperature exposure (1 h at 675°C) also induced sensitization of the grain boundaries. Identical testing on as-manufactured wrought 316L confirmed that no microstructural interfaces showed susceptibility to accelerated dissolution, and grain boundaries could be sensitized only by extended periods (24 h) at elevated temperature (675°C). Annealing was capable of removing sensitization in wrought 316L, but activated the surface of the AM 316L, leading to widespread, uniform dissolution.
ISSN:0010-9312
1938-159X
DOI:10.5006/2723