scholarly journals Change in the Microstructure of Ferritic Stainless Steel with Surface Roughness and the Number of Thermal Cycles

2021 ◽  
Author(s):  
Myoung Youp SONG
Keyword(s):  
Surface Roughness ◽  
Stainless Steel ◽  
Oxide Layer ◽  
Ferritic Stainless Steel ◽  
Exposure Time ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Thermal Cycles ◽  
Total Oxygen ◽  
Oxygen Exposure

One of the candidates for metallic interconnects of solid oxide fuel cells is ferritic stainless steel, Crofer 22 APU. Ferritic stainless steel Crofer 22 APU specimens with different surface roughness were prepared by grinding with SiC powder papers of various grits and then thermally cycled in air. Variation in the microstructure of the samples having different roughness with thermal cycling was investigated. Polished Crofer 22 APU specimens after three and five thermal cycles had relatively flat oxide layers with thicknesses of about 13.8 and 17.9 μm, respectively. Micrographs of a trench made by milling with FIB (focused ion beam) for a Crofer 22 APU specimen ground with grit 80 SiC powder paper after 8 thermal cycles (total oxygen exposure time of 200 h at 1073 K), captured by ESB (energy selective back-scattering) and SE2 (type II secondary electrons), showed that the surface of the sample was very coarse and its oxide layer was undulated. In the oxide layer, the phase of the sublayer was Cr2O3, and that of the top layer was (Cr, Mn)3O4 spinel. The surface of the sample ground with grit 80 SiC powder paper was very rough after 60 thermal cycles (total oxygen exposure time of 1500 h at 1073 K). The polished Crofer 22 APU is a better applicant to an interconnect of SOFC than those with rougher surfaces.

Study on the Variation in Microstructure of a Ferritic Stainless Steel with Surface Roughness and Thermal Cycling in Air

2021 ◽  
Vol 21 (8) ◽  
pp. 4372-4382
Author(s):  
Myoung Youp Song ◽  
Daniel R. Mumm ◽  
Young Jun Kwak
Keyword(s):  
Stainless Steel ◽  
Oxide Layer ◽  
Ferritic Stainless Steel ◽  
Exposure Time ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Thermal Cycles ◽  
Total Oxygen ◽  
Oxygen Exposure ◽  
Better Than

A ferritic stainless steel, Crofer 22 APU, is one of candidates for metallic interconnects of solid oxide fuel cells. Ferritic stainless steel Crofer 22 APU specimens with different surface roughnesses were prepared by grinding with SiC powder papers of various grits and were then thermally cycled. Polished Crofer 22 APU specimens after one thermal cycle and five thermal cycles had relatively straight oxide layers with similar thicknesses of 30 μm, suggesting that after one cycle (total oxygen exposure time of 100 h at 1073 K), the oxidation does not progress. Micrographs of a trench made by milling with the FIB (focused ion beam) for a Crofer 22 APU specimen rubbed with grit 80 SiC powder paper after 8 thermal cycles (total oxygen exposure time of 200 h at 1073 K), captured by ESB, InLens, and SE2, showed that the surface of the sample was very coarse and its oxide layer was undulated. In the oxide layer, the phase of the sublayer was Cr2O3, and that of the top layer was (Cr, Mn)3O4 spinel. The sample ground with grit 80 SiC powder paper after 60 thermal cycles (total oxygen exposure time of 1500 h at 1073 K) was very coarse. Some ridges were quite straight and continuous. After 20 and 40 thermal cycles, ASR (area specific resistance) decreased as the number of grit of the SiC powder paper increased, suggesting that the polished Crofer 22 APU is better than those with rougher surfaces for application as an interconnect of SOFC.

The Effect of Sample Preparation on the Microstructure of Austenitic-Ferritic Stainless Steel

2016 ◽  
Vol 879 ◽  
pp. 873-878 ◽  
Author(s):  
Timo Juuti ◽  
Sampo Uusikallio ◽  
Antti J. Kaijalainen ◽  
Esa Heinonen ◽  
Nyo Tun Tun ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Sample Preparation ◽  
Ferritic Stainless Steel ◽  
Laser Scanning ◽  
Focused Ion Beam ◽  
Electron Backscatter Diffraction ◽  
Ion Beam ◽  
Sample Surface ◽  
Laser Scanning Confocal Microscopy ◽  
Mechanical Polishing

Sample preparation of metastable austenitic-ferritic steels can have a significant effect on the apparent microstructure due to the transformation of austenite to martensite (γ - α'). As a result, these steels often have a complex microstructure with ferrite and martensite, which have relatively similar crystal structures, making it very difficult to analyse. However, the quantitative analysis of such microstructures and the effect of the sample preparation are very important for the further study of the steel. In this research, the effect of sample preparation in metastable austenitic-ferritic stainless steel was studied by using three different sample preparation methods. In addition to conventional mechanical etching with colloidical silica and electropolishing, focused ion beam (FIB) milling was used to create an optimal sample surface to be further analysed with electron backscatter diffraction (EBSD). Micrographs were obtained from each sample before and after sample preparation using field emission scanning electron microscopy (FESEM) and laser scanning confocal microscopy (LSCM), and the microstructure was analysed using EBSD. The surface flatness required for good EBSD analysis was significantly better using FIB milling than mechanical polishing, while electropolishing results in the greatest topography and an arched sample surface. The amount of martensite was found to be dependent on the sample preparation: least martensite was formed during electropolishing, while surprisingly mechanical polishing and FIB milling resulted in equal amounts of martensite.

Effect of Electrolyte Concentration on Anodised Titanium in Mixture of β-Glycerophosphate (β-GP) and Calcium Acetate (CA)

2015 ◽  
Vol 1087 ◽  
pp. 116-120 ◽  
Author(s):  
Te Chuan Lee ◽  
Maizlinda Izwana Idris ◽  
Hasan Zuhudi Abdullah ◽  
Charles Christopher Sorrell
Keyword(s):  
Oxide Layer ◽  
Applied Voltage ◽  
Focused Ion Beam ◽  
Electrolyte Concentration ◽  
Ion Beam ◽  
Digital Camera ◽  
Disodium Salt ◽  
Calcium Acetate ◽  
Anode Surface ◽  
Ion Diffusion

Anodic oxidation is a surface modification method which combines electric field driven metal and oxygen ion diffusion for formation of oxide layer on the anode surface. Anodised titanium has been widely use in biomedical applications especially in dental implant. This study aimed to investigate the effect of electrolyte concentration on titanium. Specifically, the titanium foil was anodised in mixture of β-glycerophosphate disodium salt pentahydrate (β-GP) and calcium acetate monohydrate (CA) with different concentration (0.02 M + 0.2 M and 0.04 M + 0.4 M), anodising time (10 min), applied voltage (150, 200, 250, 300 and 350 V) and current density (10 mA.cm-2) at room temperature. Surface oxide properties of anodised titanium were characterised by using glancing angle X-ray diffraction (GAXRD), field emission scanning electron microscope (FESEM), focused ion beam (FIB) milling and digital camera. With increasing electrolyte concentration, the oxide layer became more porous. The GAXRD results also showed that rutile formed at high applied voltage (≥300 V) when the higher concentration of electrolyte was used.

Surface roughness of a Co-less WC micro-die fabricated by focused-ion-beam machining

2004 ◽  
Vol 84 (3) ◽  
pp. 149-155 ◽  
Author(s):  
Hiroyuki Hosokawa ◽  
Koji Shimojima ◽  
Mamoru Mabuchi
Keyword(s):  
Surface Roughness ◽  
Focused Ion Beam ◽  
Ion Beam

scholarly journals Investigation on the Corrosion Behavior of Lean Duplex Stainless Steel 2404 after Aging within the 650–850 °C Temperature Range

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 529 ◽  
Author(s):  
Federica Zanotto ◽  
Vincenzo Grassi ◽  
Andrea Balbo ◽  
Fabrizio Zucchi ◽  
Cecilia Monticelli
Keyword(s):  
Stainless Steel ◽  
Grain Boundaries ◽  
Duplex Stainless Steel ◽  
Corrosion Behavior ◽  
Thermal Aging ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Localized Corrosion ◽  
Fast Diffusion ◽  
Lean Duplex Stainless Steel

This paper reports the effects of thermal aging between 650 and 850 °C on the localized corrosion behavior of lean duplex stainless steel (LDSS 2404). Critical pitting temperature (CPT) and double loop electrochemical potentiokinetic reactivation (DL-EPR) tests were performed. The localization of pitting attack and intergranular corrosion (IGC) attack after DL-EPR was investigated by optical (OM) and scanning electron microscopy (SEM) and by focused ion beam (FIB) coupled to SEM. Thermal aging caused the precipitation of mainly chromium nitrides at grain boundaries. Aging at 650 °C or short aging times (5 min) at 750 °C caused nitride precipitation mainly at α/α grain boundaries as a result of fast diffusion of chromium in this phase. Aging at 850 °C or aging times from 10 to 60 min at 750 °C also allowed the precipitation at the α/γ interface. Nitrides at γ/γ grain boundaries were observed rarely and only after long aging times (60 min) at 850 °C. Electrochemical tests showed that in as-received samples, pitting attack only affected the α phase. Conversely, in aged samples, pitting and IGC attack were detected close to nitrides in correspondence of α/α and α/γ grain boundaries depending on aging temperatures and times.

scholarly journals Formation of Nanospikes on AISI 420 Martensitic Stainless Steel under Gallium Ion Bombardment

Nanomaterials ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1492
Author(s):  
Zoran Cenev ◽  
Malte Bartenwerfer ◽  
Waldemar Klauser ◽  
Ville Jokinen ◽  
Sergej Fatikow ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Focused Ion Beam ◽  
Martensitic Stainless Steel ◽  
Incident Angle ◽  
Ion Beam ◽  
Curvature Radius ◽  
Aisi 420 ◽  
430 Stainless Steel ◽  
Aisi 316 ◽  
Aisi 430

The focused ion beam (FIB) has proven to be an extremely powerful tool for the nanometer-scale machining and patterning of nanostructures. In this work, we experimentally study the behavior of AISI 420 martensitic stainless steel when bombarded by Ga+ ions in a FIB system. The results show the formation of nanometer sized spiky structures. Utilizing the nanospiking effect, we fabricated a single-tip needle with a measured 15.15 nanometer curvature radius and a microneedle with a nanometer sized spiky surface. The nanospikes can be made straight or angled, depending on the incident angle between the sample and the beam. We also show that the nanospiking effect is present in ferritic AISI 430 stainless steel. The weak occurrence of the nanospiking effect in between nano-rough regions (nano-cliffs) was also witnessed for austenitic AISI 316 and martensitic AISI 431 stainless steel samples.

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