Role of Grain Boundaries in Intergranular Corrosion in Austenitic Stainless Steels

2002 ◽  
Author(s):  
D. N. Wasnik ◽  
V. Kain ◽  
I. Samajdar
Keyword(s):  
Stainless Steel ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Intergranular Corrosion ◽  
Austenitic Stainless Steels ◽  
304 Stainless Steel ◽  
Grain Boundary Character Distribution ◽  
Orientation Imaging ◽  
Grain Boundary Character ◽  
Degree Of Sensitization

Grain boundaries play a very important role in intergranular corrosion. They determine whether the material is prone to intergranular corrosion or not. A study has been carried out to determine the influence of grain boundaries on the degree sensitization of Type 304 stainless steel (SS) and Type 316L stainless steel. The alloys were different thermomechanical treatment to obtain a variation in grain boundaries. They were then annealed and sensitized. The degree of sensitization was evaluated by using the Double Loop Electrochemical Potentiokinetic Reactivation (DL-EPR) technique and intergranular corrosion was evaluated by ferric sulfate-sulfuric acid test. In these tests, the degree of sensitization was measured by determining the ratio of the maximum current generated by a reactivation scan to that of the anodic scan, i.e. Ir: Ia, and intergranular corrosion was measured from weight loss of specimens. The grain boundary character distribution was measured with the help of Orientation Imaging Microscope (OIM). The degree of sensitization was then related to the grain boundary measurements. It was found that the degree of sensitization and intergranular corrosion is low at high angle grain boundaries in both types of stainless steel.

DISTRIBUTION AND CORROSION BEHAVIORS OF THE TRIPLE JUNCTIONS IN A GRAIN BOUNDARY ENGINEERED 304 STAINLESS STEEL

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1110-1115 ◽  
Author(s):  
XIAOYING FANG ◽  
WEIGUO WANG ◽  
HONG GUO ◽  
CONGXIANG QIN ◽  
BANGXIN ZHOU
Keyword(s):  
Stainless Steel ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Intergranular Corrosion ◽  
Electron Back Scatter Diffraction ◽  
304 Stainless Steel ◽  
Grain Boundary Character Distribution ◽  
Triple Junctions ◽  
Grain Boundary Character ◽  
Character Distribution

Grain boundary character distribution (GBCD) and triple junction character distribution (TJCD) in a 304 stainless steel cold rolled with the thickness reduction of 6% and then annealed at 1323K for 5 minutes(GBE process) were analyzed by electron back scatter diffraction (EBSD). The intergranular corrosion (IGC) resistance of various triple junctions and grain boundaries were evaluated after sensitization treatment at 1073K for 30 minutes. The results showed special TJ containing 2 or 3 CSL boundaries exhibit higher resistance to IGC than other TJs. In addition, the {411} and {221} symmetrical tilt grain boundaries (STGBs) are more resistant to intergranular corrosion for Σ9 boundaries.

Determination of Percolation Threshold for Random Boundary Network on the Basis of EBSD/OIM Observations

2007 ◽  
Vol 539-543 ◽  
pp. 2371-2376
Author(s):  
Sadahiro Tsurekawa ◽  
Shinya Nakamichi ◽  
Tadao Watanabe
Keyword(s):  
Stainless Steel ◽  
Grain Boundary ◽  
Percolation Threshold ◽  
Grain Boundaries ◽  
Intergranular Corrosion ◽  
Polycrystalline Materials ◽  
Grain Boundary Character Distribution ◽  
Grain Boundary Engineering ◽  
Triple Junctions ◽  
Random Boundary

Grain boundary engineering through the control of grain boundary character distribution (GBCD) has been extensively employed as a powerful tool for achieving enhanced properties and for development of high performance both structural and functional polycrystalline materials. Many efforts were made firstly to increase the frequency of low-energy CSL boundaries of polycrystalline materials in grain boundary engineering. However, the connectivity of grain boundaries can be an important microstructural parameter governing bulk properties of polycrystalline materials as well as the GBCD. In the present work, the connectivity of random grain boundaries was quantitatively evaluated using both the triple junction distribution and random boundary cluster length on the basis of SEM-EBSD/OIM observations, and then these evaluated parameters were linked to intergranular corrosion of SUS304 stainless steel. We have found that the length of the maximum random boundary cluster drastically decrease with increasing CSL boundaries in the fraction ranging 60 – 80% CSL boundaries, which leads to percolation threshold occurring at approximately 70±5% CSL boundary fraction (at 30±5% random boundary fraction). The experimentally observed percolation threshold is much higher than theoretically obtained one based on randomly assembled network (at 35% resistant bonds for a 2D hexagonal lattice). In addition, the fraction of resistant triple junctions is found to increase with increasing the the CSL boundary fraction. An increase in the frequency of resistant triple junctions can enhance intergranular corrosion resistance of polycrystalline austenitic stainless steel even if the GBCD is the same.

The Relationship between Grain Boundary Character Distribution and Intergranular Corrosion Resistance of 304 Austenitic Stainless Steel

2011 ◽  
Vol 689 ◽  
pp. 239-244
Author(s):  
Xiao Ying Fang ◽  
Xiao Cui ◽  
Cong Xiang Qin ◽  
Wei Guo Wang
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Grain Boundary ◽  
Intergranular Corrosion ◽  
Electron Backscatter Diffraction ◽  
Grain Boundary Character Distribution ◽  
Surface Appearance ◽  
Boundary Character ◽  
Grain Boundary Character ◽  
304 Austenitic Stainless Steel

A wedge-shaped 304 austenitic stainless steel with varied thickness longitudinally was cold rolled into a flat one and then annealed at 1323K for 10 min. The grain boundary character distributions (GBCDs) in the specimen as processed were examined by the means of Electron backscatter diffraction (EBSD). The results showed that, at the regions with low pre-strains ranged from 4% to 6%, quite high fractions of S3n (n=0,1,2,3) grain boundaries and large-sized S3n (n=0,1,2,3) grain clusters are introduced compared with the regions of quite low ( less than 2.5%) or relatively high pre-strain. The surface appearance of after corrosion test reveals that grain dropping due to intergranular corrosion (IGC) is depressed and the penetration of IGC from the surface into the interior in the cross-section is arrested significantly as well in the regions with high fractions of S3n boundaries and large-sized S3n grain clusters.

Thermal Stability of Microstructure in Grain Boundary Character Distribution-Optimized and Cold-Worked Austenitic Stainless Steel Developed for Nuclear Reactor Application

2009 ◽  
Vol 1215 ◽  
Author(s):  
Shinichiro Yamashita ◽  
Yasuhide Yano ◽  
Ryusuke Tanikawa ◽  
Norihito Sakaguchi ◽  
Seiichi Watanabe ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Grain Boundary Character Distribution ◽  
Boundary Character ◽  
Grain Boundary Character ◽  
Character Distribution ◽  
Boundary Character Distribution ◽  
Cold Worked

AbstractGrain boundary character distribution-optimized (GBCD) Type 316 corresponding austenitic stainless steel and its cold-worked ones (GBCD+CW) are one of prospective nuclear materials to be considered for next generation energy systems. These steels were thermally-aged at 973 K for 1 and 100 h and were examined by transmission electron microscopy (TEM) to evaluate microstructural stability during high temperature exposure. TEM results revealed that microstructures of both specimens prior to ageing contained step-wise boundaries which is composed of coincidence site lattice (CSL) and random grain boundaries and also that the GBCD+CW specimens had dislocation cells and networks as well as deformation twins whereas as the GBCD one possessed few dislocations. After thermal ageing, the precipitates formed on not only random grain boundaries but also dislocations, contributing to prevent significant microstructural change occurring such as recrystallization and dislocation recovery.

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