Relationship between microstructure and fracture types in a UNS S32205 duplex stainless steel

Duplex stainless steels are susceptible to the formation of sigma phase at high temperature which could potentially be responsible for catastrophic service failure of components. Thermal treatments were applied to duplex stainless steels in order to promote the precipitation of different fractions of sigma phase into a ferrite-austenite microstructure. Quantitative image analysis was employed to characterize the microstructure and Charpy impact tests were used in order to evaluate the mechanical degradation caused by sigma phase presence. The fracture morphology of the Charpy test specimens were thoroughly observed in SEM, looking for a correlation between the microstructure and the fracture types in UNS S32205 duplex stainless steel. The main conclusion is the strong embrittlement effect of sigma phase since it is possible to observe a transition from transgranular fracture to intergranular fracture as increases the percentage of sigma phase. Thus, the mixed modes of fracture are predominant in the present study with high dependence on sigma phase percentages obtained by different thermal treatments

Isothermal and Cyclic Aging of 310S Austenitic Stainless Steel

Unusual damage and high creep strain rates have been observed on components made of 310S stainless steel subjected to thermal cycles between room temperature and 1143 K (870 °C). Microstructural characterization of such components after service evidenced high contents in sigma phase which formed first from δ-ferrite and then from γ-austenite. To get some insight into this microstructural evolution, isothermal and cyclic aging of 310S stainless steel has been studied experimentally and discussed on the basis of numerical simulations. The higher contents of sigma phase observed after cyclic agings than after isothermal treatments are clearly associated with nucleation triggered by thermal cycling

Is There an Association between Long-Term Sick Leave and Disability Pension and Unemployment beyond the Effect of Health Status? – A Cohort Study

Background: Studies have shown that long-term sick leave is a strong predictor of disability pension. However, few have aimed to disentangle the effect of sick leave and of health status. The objective of this study was to investigate whether there is an association between long-term sick leave and disability pension and unemployment, when taking health status into account. Methods/Principal Findings: The study was based on the Stockholm Public Health Cohort, restricted to 13,027 employed individuals (45.9 % men) aged 18–59 in 2002 and followed until 2007. Hazard ratios (HR) with 95 % Confidence Interval (CI) were estimated by Cox regression models adjusting for socio-demographic factors and five measures of health status. Having been on long-term sick leave increased the risk of disability pension (HR 4.01; 95 % CI 3.19–5.05) and longterm unemployment (HR 1.45; 95 % CI 1.05–2.00), after adjustment for health status. The analyses of long-term sick leave due to specific illness showed that the increased risk for long-term unemployment was confined to the group on sick leave due to musculoskeletal (HR 1.70 95 % CI 1.00–2.89) and mental illness (HR 1.80 95 % CI 1.13–2.88) and further that there was an increased risk for short-term unemployment in the group on sick leave due to mental illness (HR1.57 95%CI 1.09–2.26). Conclusions/Significance: Long-term sick leave increases the risks of both disability pension and unemployment even when taking health status into account. The results support the hypothesis that long-term sick leave may start a process o

Characterization of thermal oxide films formed on a duplex stainless steel by means of confocal-Raman microscopy and electrochemical techniques

In this work oxide films have been developed on the surface of a duplex stainless steel (UNS 1.4462) using high temperature confocal microscopy to follow their growth. The characteristics of these oxide films have been analyzed by means of weight-gain measurements, Raman microscopy and electrochemical techniques, namely potentiodynamic polarization curves and electrochemical impedance spectroscopy. The results show an increase in the amount of oxides (particularly γ-Fe2O3 and Fe3O4) with temperature. Regarding the electrochemical properties of these films, the corrosion resistance of the film tends to be lower with the heat treatment temperature, probably due to a more porous and heterogeneous scale. Mott–Schottky plots show the n-type semiconductive behavior of the films with donor densities that decrease with the enhancement of the temperature.We wish to express our gratitude to MICINN (CTQ2009-07518) (UPVO8-3E-012), to Universitat Politecnica de Valencia (CEI-01-11), to the Generalitat Valenciana for its help in the CLSM acquisition (MY08/ISIRM/S/100), and to Dr. Asuncion Jaime for her translation assistance.Sánchez Tovar, R.; Leiva García, R.; García Antón, J. (2015). Characterization of thermal oxide films formed on a duplex stainless steel by means of confocal-Raman microscopy and electrochemical techniques. Thin Solid Films. 576:1-10. https://doi.org/10.1016/j.tsf.2014.12.024S11057

Study of the sensitisation process of a duplex stainless steel (UNS 1.4462) by means of confocal microscopy and localised electrochemical techniques

When duplex stainless steels are heated, they can become sensitised and intermetallic phases can appear. In this work, samples of duplex stainless steel, UNS 1.4462, have been heated (850 degrees C for 1 and 2 h) in a heating unit that can be accommodated to a confocal microscope in order to study the morphological changes in-situ. The electrochemical behaviour of the samples has been analysed by means of conventional and localised electrochemical techniques. According to the results, there is a general decrease in the steel resistance to localised corrosion; this decrease can be related to defects in the formed passive film.We wish to express our gratitude to MICINN (CTQ2009-07518), to Universitat Politecnica de Valencia (CEI-01-11), to the Generalitat Valenciana for its help in the CLSM acquisition (MY08/ISIRM/S/100), to Professor Alda Simoes and Andreia Marques for the help on LEIS measurements and to Dr. Asuncion Jaime for her translation assistance.Leiva García, R.; Fernandes, JS.; Muñoz-Portero, M.; Garcia-Anton, J. (2015). Study of the sensitisation process of a duplex stainless steel (UNS 1.4462) by means of confocal microscopy and localised electrochemical techniques. Corrosion Science. 94:327-341. https://doi.org/10.1016/j.corsci.2015.02.016S3273419