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Caliskan H.,Bartyn University | Erdogan A.,Bartyn University | Panjan P.,Jozef Stefan Institute | Gok M.S.,Bartyn University | Karaoglanli A.C.,Bartyn University
Materiali in Tehnologije | Year: 2013

Nanostructured hard coatings are widely used to improve the wear resistance of tool steels in tribological applications. These coatings generally work under abrasive conditions and, therefore, a determination of their abrasive wear resistance has great importance. In this study, the free-ball micro-scale abrasion test, based on the ball-crater technique, has been used to evaluate the wear resistance of a multilayer nanocomposite nc-TiAlSiN/TiSiN/TiAlN hard coating. The coating was deposited on the AISI H11 cold-work tool steel using the industrial magnetron sputtering system. The microhardness and adhesion of the coating to the substrate were measured with the nanoindentation and scratch tests, respectively. The wear tests have been performed using SiC abrasive slurry on ball-cratering equipment. The crater-wear volumes have been evaluated using an optical microscope (OM). An analysis of the worn craters was conducted with a scanning electron microscope (SEM). It was found that the nc-TiAlSiN/TiSiN/TiAlN hard coating has a better adhesion to the AISI H11 steel substrate and a higher abrasive wear resistance than a conventional TiN coating. A two-fold increase in the sliding speed resulted in an approximately two-fold increase in the removed-wear volume. Three different wear mechanisms, i.e., micro-scratch, lateral fracture and plastic deformation, took place on the craters formed on the nc-TiAlSiN/TiSiN/TiAlN coated steel.

Aytekin H.,Afyon Kocatepe University | Said G.,Bartyn University | Aktapb D.,Bartyn University
Strength of Materials | Year: 2015

In this study, a mathematical approach was presented to theoretically determine the change of the yield strength of bcc metals and alloys with temperature and strain rate, which can be determined for any desired strain rate by conducting experiments at two different strain rates. © 2015 Springer Science+Business Media New York.

Varol T.,Bartyn University | Ertugrul M.,Bartyn University
Fresenius Environmental Bulletin | Year: 2015

The climate change has significant effects on the fire activity. Fire statistics in Turkey have been kept since 1937. When these records are analyzed, it can be seen that the large fires have been more active in the Mediterranean region after 1990, while the small fires have been active in the Aegean region. When top 5 years, in which large fires are seen in the Mediterranean region, are examined, there is 14.75 times increase in terms of the area burned in fires that occurred after 1990. In the Aegean region, where the number of small fires is at highest, there are no fires before 1990 in the largest five fires in respect of burned area. In the fires that occurred after 1990, 5% of the forests of the Mediterranean region and 2% of the forests of the Aegean region have been damaged. In this article, the fire statistics obtained from the General Directorate of Forestry and climate data obtained from General Directorate of Meteorology for the years 1973-2009 were used. The statistical analysis of the fire and climate data of 36 years indicates that the fire activity in both regions has increased. © by PSP.

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