Effect of Cr Addition on Properties and Tribological Behavior at Elevated Temperature of Boride Layers Grown on Borosintered Powder Metallurgy Alloys

Ali Günen,Ömer Saltuk Bölükbaşı,Yasin Özgürlük,Derviş Özkan,Okan Odabaş,İlyas Somunkıran 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.3

This study focused on chromium addition (0 wt%, 3 wt%, 6 wt%, 9 wt% and 12 wt%) on the boride layer formation, microhardness,fracture toughness and elevated temperature friction and wear behaviour of alloys formed by powder metallurgy(P/M). The boride layers obtained on P/M alloys were characterized by examining density, porosity, surface roughness,scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, surface profilometry, microhardness,and fracture toughness. The addition of Cr has a significant effect on both boride layer formation and friction-wearbehaviour of P/M alloys. Increasing the Cr addition up to 6 wt% has an improving effect on the microhardness, fracturetoughness and wear resistance of the P/M alloys, whereas in the case of 9–12 wt% Cr addition causes exfoliation in the boridelayer and low fracture toughness, thus reducing wear resistance. Coefficients of friction and wear volume losses at elevatedtemperatures are higher than room temperature. The best wear resistance at room temperature was obtained in the samplecontaining 3 wt% Cr with the highest fracture toughness, while the best wear resistance at 250 °C and 500 °C was obtainedin the sample containing 6 wt% Cr, where the highest hardness value was obtained.

Pack-Boriding of Monel 400: Microstructural Characterization and Boriding Kinetics

Ali Günen,Mourad Keddam,Azmi Erdoğan,Mustafa Serdar Karakaş 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.8

Monel 400 was pack-borided in the temperature range of 1173–1273 K for exposure times of 2–6 h. The boride layersproduced on the surface of the alloy were examined by scanning electron microscopy and phase identification was carriedout by X-ray diffraction. The topmost layer on the borided Monel 400 was compact and contained the Ni2Bphase whilethe diffusion zone contained grain boundary precipitates of borides. Boride layers of 35–290 μm thickness and 1002–1476HV0.025hardness were obtained. SEM observations revealed a smooth interface between the boride layer and the diffusionzone. A kinetic model based on the integral method was applied to investigate the kinetics of Ni2Blayer. The boron activationenergy in the Ni2Blayer was estimated as equal to 300.7 kJ mol−1. An experimental validation of the model was madeby comparing the experimental layer thicknesses obtained, after boriding at 1198 K for 1 and 3 h, with predicted values.

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.

Properties of Aluminum Nano Composites Bearing Alumina Particles and Multiwall Carbon Nanotubes Manufactured by Mechanical Alloying and Microwave Sintering

Ali Günen,Ömer Saltuk Bölükbaşı,Yasin Özgürlük,Derviş Özkan,Okan Odabaş,İlyas Somunkıran 대한금속ᆞ재료학회 2023 METALS AND MATERIALS International Vol.29 No.2

This study focused on chromium addition (0 wt%, 3 wt%, 6 wt%, 9 wt% and 12 wt%) on the boride layer formation, microhardness,fracture toughness and elevated temperature friction and wear behaviour of alloys formed by powder metallurgy(P/M). The boride layers obtained on P/M alloys were characterized by examining density, porosity, surface roughness,scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, surface profilometry, microhardness,and fracture toughness. The addition of Cr has a significant effect on both boride layer formation and friction-wearbehaviour of P/M alloys. Increasing the Cr addition up to 6 wt% has an improving effect on the microhardness, fracturetoughness and wear resistance of the P/M alloys, whereas in the case of 9–12 wt% Cr addition causes exfoliation in the boridelayer and low fracture toughness, thus reducing wear resistance. Coefficients of friction and wear volume losses at elevatedtemperatures are higher than room temperature. The best wear resistance at room temperature was obtained in the samplecontaining 3 wt% Cr with the highest fracture toughness, while the best wear resistance at 250 °C and 500 °C was obtainedin the sample containing 6 wt% Cr, where the highest hardness value was obtained.

Characterisation of Phenotypic and Genotypic Antibiotic Resistance Profile of Enterococci from Cheeses in Turkey

Cemil Kürekci,Sevda Pehlivanlar Önen,Mustafa Yipel,Özkan Aslantas,Aycan Gündogdu 한국축산식품학회 2016 한국축산식품학회지 Vol.36 No.3

The aim of this study was to determine the prevalence of enterococci in cheese samples and to characterize their antimicrobial resistance profiles as well as the associated resistance genes. A total of 139 enterococci were isolated from 99 cheese samples, the isolates were identified as E. faecalis (61.2%), E. faecium (15.1%), E. gallinarum (12.9%), E. durans (5.0%), E. casseliflavis (2.9%) and E. avium (2.9%). The most frequent antimicrobial resistance observed in enterococci isolates was to lincomycin (88.5%), followed by kanamycin (84.2%), gentamycin (low level, 51.1%), rifampin (46.8%) and tetracycline (33.8%). Among the isolates, the frequencies of high level gentamycin and streptomycin resistant enterococci strains were 2.2% and 5.8%, respectively. Apart from the mentioned antibiotics, low levels of resistance to ciprofloxacin, erythromycin and chloramphenicol were found. Moreover no resistance was observed against penicillin and ampicillin. The antimicrobial resistance genes including tetM, tetL, ermB, cat, aph(3’)-IIIa, ant(6)-Ia and aac(6’)-Ieaph(2’’)-Ia were found in enterococci from Turkish cheese samples. In the current study, we provided data for antibiotic resistance and the occurrence of resistance genes among enterococci. Regulatory and quality control programs for milk and other dairy products from farms to retail outlets has to be established and strengthened to monitor trends in antimicrobial resistance among emerging food borne pathogens in Turkey.

Proangiogenic Hypoxia-Mimicking Agents Attenuate Osteogenic Potential of Adipose Stem/Stromal Cells

Abu-Shahba Ahmed G.,Gebraad Arjen,Kaur Sippy,Paananen Riku O.,Peltoniemi Hilkka,Seppänen-Kaijansinkko Riitta,Mannerström Bettina 한국조직공학과 재생의학회 2020 조직공학과 재생의학 Vol.17 No.4

BACKGROUND: Insufficient vascularization hampers bone tissue engineering strategies for reconstructing large bone defects. Delivery of prolyl-hydroxylase inhibitors (PHIs) is an interesting approach to upregulate vascular endothelial growth factor (VEGF) by mimicking hypoxic stabilization of hypoxia-inducible factor-1alpha (HIF-1α). This study assessed two PHIs: dimethyloxalylglycine (DMOG) and baicalein for their effects on human adipose tissue-derived mesenchymal stem/stromal cells (AT-MSCs). METHODS: Isolated AT-MSCs were characterized and treated with PHIs to assess the cellular proliferation response. Immunostaining and western-blots served to verify the HIF-1α stabilization response. The optimized concentrations for long-term treatment were tested for their effects on the cell cycle, apoptosis, cytokine secretion, and osteogenic differentiation of AT-MSCs. Gene expression levels were evaluated for alkaline phosphatase (ALPL), bone morphogenetic protein 2 (BMP2), runt-related transcription factor 2 (RUNX2), vascular endothelial growth factor A (VEGFA), secreted phosphoprotein 1 (SPP1), and collagen type I alpha 1 (COL1A1). In addition, stemness-related genes Kruppel-like factor 4 (KLF4), Nanog homeobox (NANOG), and octamer-binding transcription factor 4 (OCT4) were assessed. RESULTS: PHIs stabilized HIF-1α in a dose-dependent manner and showed evident dose- and time dependent antiproliferative effects. With doses maintaining proliferation, DMOG and baicalein diminished the effect of osteogenic induction on the expression of RUNX2, ALPL, and COL1A1, and suppressed the formation of mineralized matrix. Suppressed osteogenic response of AT-MSCs was accompanied by an upregulation of stemness-related genes. CONCLUSION: PHIs significantly reduced the osteogenic differentiation of AT-MSCs and rather upregulated stemness-related genes. PHIs proangiogenic potential should be weighed against their longterm direct inhibitory effects on the osteogenic differentiation of AT-MSCs.

The Process of Branding a City

Cemal Yü,kselen,Emel Gö,nenç,Gü,ler,R,Ayş,en Wolff 세계문화관광학회 2010 International Journal of Culture and tourism Resea Vol.3 No.1

In studies about the branding of destinations, one finds the need to involve all the local and international stakeholders in the process of SWOT analysis and prepare a unique action plan. The Brand Destination Project of the Ministry of Culture and Tourism in Turkey is interested in making various famous cities culturally attractive to tourists. They expect economic and social development as they carry their historical values into the future. Antioch, the ancient name of Antakya, is one of the destinations targeted for branding in this project. Antioch was once the third largest trade and tourism center in the Roman Empire. It was also one of the first places to become a center for Christianity, drawing many pilgrims. It was a melting pot for many ancient civilizations in Anatolia. The purpose of this paper is to brand Antioch as a place where people have been living in the spirit of tolerance and brotherhood for many centuries against the backdrop of different religions and ethnicities. Furthermore, this paper includes suggestions for branding processes, responsibilities of stakeholders, and conclusions which may be realized by SWOT analysis and other exploratory research.

The Process of Branding a City

Cemal Yü,kselen,Emel Gö,nenç,Gü,ler,R. AyĢ,en Wolff 세계문화관광학회 2010 Conference Proceedings Vol.11 No.0

In studies about the branding of destinations, one finds the need to involve all the local and international stakeholders in the process of SWOT analysis and prepare a unique action plan. The Brand Destination Project of the Ministry of Culture and Tourism in Turkey is interested in making various famous cities culturally attractive to tourists. They expect economic and social development as they carry their historical values into the future. Antioch, the ancient name of Antakya, is one of the destinations targeted for branding in this project. Antioch was once the third largest trade and tourism center in the Roman Empire. It was also one of the first places to become a center for Christianity, drawing many pilgrims. It was a melting pot for many ancient civilizations in Anatolia. The purpose of this paper is to brand Antioch as a place where people have been living in the spirit of tolerance and brotherhood for many centuries against the backdrop of different religions and ethnicities. Furthermore, this paper includes suggestions for branding processes, responsibilities of stakeholders, and conclusions which may be realized by SWOT analysis and other exploratory research.