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Properties and Corrosion Resistance of AISI H13 Hot-Work Tool Steel with Borided B4C Powders
Ali Günen,İsmail Hakki Karahan,Mustafa Serdar Karakaş,Bülent Kurt,Yusuf Kanca,Vedat Veli Çay,Murat Yıldız 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.9
In this study, the surface of AISI H13 steel was borided with powder blends of B4Cand NaBF4using the powder-pack methodat 800, 900 and 1000 °C for 2, 4 and 6 h. The structural and mechanical characteristics of the boride layers formed on thesurface were characterized using scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometry, 2Dsurface profilometry, microhardness and electrochemical corrosion (3.5 wt% NaCl) tests. The boride layer exhibited a singlephase structure (Fe2B) in samples coated at 800 °C and a dual-phase structure (FeB + Fe2B) at higher boriding temperatures(900 and 1000 °C). The boride layers were compact and crack-free in all boriding conditions. Depending on boridingparameters, the thickness, hardness and average surface roughness (Ra) of the coatings were found to range between 5.81and 102.46 μm, 1635–1915 HV and 0.315–0.650 μm, respectively. The borided AISI H13 steel displayed up to 33.5 timesand 2.4 times higher corrosion resistance than untreated AISI H13 steel and martensitic AISI 431 steel, respectively. Thissuggests potential use of borided AISI H13 steel in the steam turbines and marine applications as an alternative to the morecostly martensitic and duplex stainless steel grades. The corrosion resistance depended on the phase structure (single- ordual-layer), density, thickness and surface roughness of the boride coatings.
Güray Can,Emrah Poşul,Bülent Yılmaz,Hatice Can,Uğur Korkmaz,Fatih Ermiş,Mevlüt Kurt,Ülkü Dağlı 대한내과학회 2019 The Korean Journal of Internal Medicine Vol.34 No.3
Background/Aims: There are only a few epidemiological study about inflammatory bowel disease in the last 10 years in Turkey, especially in Western Blacksea region. In our study, we aimed to identify the changes in the incidence and the prevalence of inflammatory bowel disease in Western Blacksea region at the last 10 years. Methods: Totally 223 patients with inf lammatory bowel disease (160 ulcerative colitis, 63 Crohn’s disease) were enrolled in the study followed up between 2004 to 2013 years. The epidemiological characteristics of patients were recorded. Results: The prevalences were 12.53/105 and 31.83/105 for Crohn’s disease and ulcerative colitis respectively. Mean annual incidences increased from 0.99/105 and 0.45/105 for ulcerative colitis and Crohn’s disease (2004 to 2005 years) to 4.87/105 and 2.09/105 for ulcerative colitis and Crohn’s disease respectively (2011 to 2013 years). While the prevalence was higher in urban areas in Crohn’s disease (12.60/105), it was higher in rural areas in ulcerative colitis (36.17/105). In ulcerative colitis, mean annual incidences were 2.91/105 and 2.86/105 for urban and rural areas respectively. In Crohn’s disease, they were 1.37/105 and 1.08/105 for urban and rural areas respectively. Conclusions: The incidence of inflammatory bowel disease seems to increase in Western Blacksea region at the last 10 years. This increment is more prevalent in rural areas.