Tracking the evolution of intergranular corrosion through twin-related domains in grain boundary networks

Christopher M Barr,Wayne Harlow,Sebastian Thomas,James L Hart,Elaf Anber,Mitra L Taheri

doi:10.1038/s41529-018-0032-7

Christopher M Barr, Wayne Harlow + Show 4 more

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https://doi.org/10.1038/s41529-018-0032-7

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Abstract

Tailoring the grain boundary network is desired to improve grain boundary-dependent phenomena such as intergranular corrosion. An important grain boundary network descriptor in heavily twinned microstructures is the twin-related domain, a cluster of twin-related grains. We indicate the advantages of using twin-related domains and subsequent statistics to provide new insight into how a grain boundary networks respond to intergranular corrosion in a heavily twinned grain boundary engineered 316L stainless steel. The results highlight that intergranular corrosion is typically arrested inside twin-related domains at coherent twins or low-angle grain boundaries. Isolated scenarios exist, however, where intergranular corrosion propagation persists in the grain boundary network through higher-order twin-related boundaries.

Highlights

Austenitic stainless steels including 304/304L and 316L are critical structural alloys used in a diverse number of engineering applications due to a combination of good mechanical properties, weldability, and overall corrosion resistance
The results indicate that intergranular corrosion (IGC) has a systematically different response at locations at the exterior and interior of a twin-related domains (TRD)
At the exterior of the TRDs, the random grain boundary (GB) network was typically shown to be susceptible to IGC propagation

Summary

Introduction

Austenitic stainless steels including 304/304L and 316L are critical structural alloys used in a diverse number of engineering applications due to a combination of good mechanical properties, weldability, and overall corrosion resistance. Intergranular corrosion (IGC) in austenitic stainless steels and other alloys can have a devastating effect on many of these industries, including nuclear, naval ship structures, high temperature processing equipment, and off-shore wind turbines. GB sensitization can occur during welding and heat treatment in the 500–800 °C temperature regime and results in the precipitation and growth of deleterious GB Cr-rich carbides and subsequent Cr-depleted zones.[1,2,3] Significant effort has been made to mitigate the deleterious effects of sensitization by introducing a high density of GBs resistant both Cr-rich carbide formation and IGC through grain boundary engineering (GBE).[4,5,6,7,8,9,10] GBE is the process of introducing a specific type and density of GBs through thermomechanical processing (TMP) to improve a GB-dependent property. Previous studies have shown GBE to be a successful method in mitigating intergranular stress corrosion cracking,[11,12] IGC,[5,13,14] hydrogen embrittlement,[15] and grain growth.[16]

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