Papers by Keyword: Austenitic Stainless Steel

Abstract: After being plasma carburized, the surface of AISI 316 austenitic stainless steel was covered with a layer of compact black thin-film. The surface polishing treatment, electrochemical brightening was carried out to remove the black thin-film and renew the original color of the stainless steel. The surface appearance, microstructures, micro hardness, surface roughness and corrosion resistance of the samples treated by electrochemical brightening process were analyzed. Experimental results show that the electrochemical brightening treatment can remove the black thin-film from and restore the original color of the plasma carburized stainless steel. After electrochemical brightening treatment, the thickness and surface hardness of the carburized layer were all decreased little, but the corrosion resistance was improved significantly. And the surface roughness (Ra) was lower than before. Therefore, the electrochemical surface brightening treatment can be used to improve the surface quality of the austenitic stainless steel treated by plasma carburizing.

Abstract: Differential scanning calorimetry was used to study melt and solidification and microstructure of austenitic stainless steels containing boron. The liquidus and solidus temperatures decreased because of the boron content, and boron inhibited the formation of δ-Fe. A large content of eutectic boride structure was detected when the boron content was higher. The boride was M2B, and the crystal structure was orthorhombic. The crystal structure and elemental composition of M2B were investigated in detail by SEM-EDS and XRD analysis.

Abstract: Nuclear spent fuel reprocessing and waste management plants use nitric acid as process fluid and type 304 L stainless steel as construction material. Tubular products like bars, tubes and pipes are prone to End Grain Corrosion from the exposed cross-sectional surfaces. In this study, type 304 L stainless steel is subjected to different heat treatment to induce selective segregation of phosphorus. The susceptibility to End Grain Corrosion was established in tests using boiling nitric acid containing oxidizing Cr(VI) ions. A clear effect on End Grain Corrosion was found for heat treatment reported to induce phosphorus segregation. Finally, specific annealing heat treatment is developed that erases out the segregation, without affecting the grain size or sensitization.

Abstract: The origin and role of S3 boundaries during dynamic recrystallization (DRX) and grain boundary engineering (GBE) of a Ti-modified austenitic stainless steel (alloy D9) is studied. Hot deformation tests were carried out on solution-annealed (SA) specimens to study the DRX behavior whereas a series of cold deformation and annealing were performed on SA specimens to realize GBE microstructure. A linear relationship between the area fraction of DRX and the number fraction of Σ3 boundaries was observed during hot deformation. This high fraction of Σ3 boundaries could account for the formation of coherent annealing twins by “growth accidents” during DRX. For certain combinations of cold deformation and annealing, a significant increase in S3 boundaries was observed. In contrast to hot deformation, majority of these new S3 boundaries during cold deformation and annealing were formed by geometrical interactions between the pre-existing Σ3 boundaries. The role of the S3 boundaries during DRX and on tailoring microstructure through grain boundary engineering approach is discussed.

Abstract: In order to form thin metal sleeve with the thickness of 0.03 mm, type 304 austenitic steel sheet was deeply drawn to a cup and spinning method applied to its body. The sleeve shows high strength with a dual-phase microstructure of fine austenite and transformed martensite. Pancaked austenite and martensite grains were highly elongated along RD (drawing direction) in the layer structure, and their grain width was about 100 nm. Dynamically recovered austenite grains were highly aligned from {101} to {101}. The strain-induced martensite grains mainly showed two components of {001} and {111}. Recover and recrystallization of the sleeve appeared at the temperature from 873 K to 1073 K. Annealed at 1073 K the austenite grains were mostly recrystallized with intensifying {101}, and the martensite grains were also reverse-transformed to austenite.

Abstract: The present study aims to understand the evolution of microstructure leading to nano/ultrafine grain formation during cyclic thermal process. A commercial grade of AISI 304L austenitic SS was cold rolled which resulted in a creation of a dual microstructure having strain induced martensite (43%) and heavily deformed retained austenite. The dual phase microstructure was subjected to cyclic thermal annealing process at 825 °C. The events occurring in; a) retained austenite and b) reverted austenite formed by phase reversion of strain induced martensite, during annealing treatment, were studied by the Electron backscattered diffraction (EBSD). The study revealed recrystallisation process of the two austenite grains, which resulted into ultrafine grain formation during cyclic thermal process.

Abstract: There has recently been significant interest in the problem of variant selection in the strain-induced transformation of austenite to α’-martensite in metastable austenitic stainless steels. Previous work has highlighted our poor understanding of the mechanisms leading to this transformation, in particular the role that the macroscopic stress plays in the transformation. In this work, we have sought to perform detailed experiments aimed at developing a statistical grain level view of variant selection in one particular grade of austenitic stainless steel. EBSD measurements made over a large number of grains as well as macroscopic texture measurements made at different levels of imposed plastic strain allow for comparison against various approaches for predicting variant selection based on the Patel-Cohen interaction energy.

Abstract: The microstructure evolution and the dynamic processes of grain refinement in a 304-type austenitic stainless steel during multiple calibre hot rolling at temperatures of 700-1000°C were studied. The structural changes are characterized by the elongation of original grains towards the rolling axis and the development of new fine grains, the mean size of which decreases with decreasing the deformation temperature. During multiple rolling at 1000°C, the new grains resulted from the development of discontinuous dynamic recrystallization involving a bulging of frequently corrugated grain boundaries. On the other hand, the new grain boundaries leading to remarkable refinement of original microstructure were developed at temperatures below 800°C as a result of continuous strain-induced reactions.

Abstract: Plain fatigue and fretting fatigue tests of sensitized SUS304 stainless steel under pressurized hot water at 7.3MPa and 288°C have been carried out. Fatigue strengths for both fatigue tests almost coincided. Fretting contact could nucleate small SCC cracks near the contact edge in the direction perpendicular to cyclic loading. High R–ratio reduced fatigue strength due to longer exposure time to corrosive environment at high mean stress. From the constant load SCC tests of the specimen with small SCC pre–crack induced by fretting contact, it was found that the threshold stress intensity factor for growth of small SCC precrack was 4.1MPa·m^1/2, which was significantly lower than that for long crack (10MPa·m^1/2).

Abstract: The stainless steel is more and more applications to the medical field; the most is the austenitic stainless steel. In this paper, 00Cr₁₈Ni₁₄Mo₃ mechanical properties of austenitic stainless steel screw, compared to the solution of the former and the sample microstructure after solution treatment, energy spectrum and the torque angle reverse faults, compared to solution treatment found that mechanical properties of the samples after meet the standard can be applied to practice.