Person: SARIOĞLU, CEVAT
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SARIOĞLU
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CEVAT
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Publication Metadata only Residual stresses in (Zr,Hf)N films (up to 11.9 at.% Hf) measured by X-ray diffraction using experimentally calculated XECs(ELSEVIER SCIENCE SA, 2005) SARIOĞLU, CEVAT; Atar, E; Sarioglu, C; Cimenoglu, H; Kayali, ESIn the present work, the residual stresses of (Zr,Hf)N films were measured using X-ray diffraction (XRD) fixed incident multiplane technique (FIM) for varying amounts of Hf addition by assuming the film was isotropic and anisotropic (Kronel model). The residual stress values calculated according to isotropic and anisotropic models were almost the same (-6 GPa). Addition up to 11.9 at.% Hf into ZrN films did not affect the level of residual stress. (C) 2004 Elsevier B.V. All rights reserved.Publication Metadata only The effect of anisotropy on residual stress values and modification of Serruys approach to residual stress calculations for coatings such as TiN, ZrN and HfN(ELSEVIER SCIENCE SA, 2006) SARIOĞLU, CEVAT; Sarioglu, CevatThe residual stresses in literature on hard coatings (e.g., TiN, CrN, HfN and ZrN) are usually calculated using the mechanical elastic constants often determined by indentation technique by assuming isotropic behavior. The effect of anisotropy of the hard coatings on residual stress values such as TiN, ZrN and HfN has been documented using classical technique and Thin Film techniques (fixed incidence multiplane (FIM) Technique). Due to lack of the single crystal data, the anisotropy of coatings has been taken into account through XECs determined experimentally for ZrN, HfN and TiN films. Recently, single crystal elastic constants of the ZrN, HfN and NbN have been measured. In the light of single crystal elastic constant data, residual stresses reported in the literature were reevaluated according to Reuss, Voigt, Hill (or mixed) and Kroner models using the best fitting approach after modifying Serruys approach. The modified Serruys approach captures the anisotropic behavior of coatings such as ZrN and Zr(Hf)N. The residual stress calculations were improved and the residual stress values were significantly increased as high as 30% compared to the previously published data. The best fitting approach (modified Serruys approach) was compared to the procedure used by Perry using experimentally determined XECs. (c) 2006 Elsevier B.V. All rights reserved.Publication Metadata only Analysis of XRD stress measurement data of naturally grown oxide films Al2O3 and Cr2O3 based on existing Reuss, Voigt, and Hill models(MANEY PUBLISHING, 2002) SARIOĞLU, CEVAT; Sarioglu, CThe resistance of naturally grown alumina (Al2O3) and chromia (Cr2O3) scales to cracking and spalling under influence of growth and thermal stresses is a critical aspect of the environmental resistance of high temperature alloys such as Fe and Ni based alloys. The driving force for scale failure is the residual stress developed in the scale. In this study, strain and stress measurement techniques by XRD were reviewed. XRD data for Al2O3 and Cr2O3 films were analysed and discussed with respect to existing models. It was experimentally found that the Reuss model provided the best description of the measured strain data for these films. Strain and stress states of Al2O3 and Cr2O3 films here determined. (C) 2002 IoM Communications Ltd.Publication Metadata only X-ray determination of stresses in alumina scales on high temperature alloys(SCIENCE REVIEWS 2000 LTD, 2000) SARIOĞLU, CEVAT; Sarioglu, C; Schumann, E; Blachere, JR; Pettit, FS; Meier, GHThe resistance of alumina scales to cracking and spalling under the influence of growth and thermal stresses is a critical aspect of the environmental resistance of high temperature structural alloys, oxidation resistant coatings, and bond coats for thermal barrier coatings. However, the relative magnitudes of the stresses and their distribution are often not known. In this study several X-ray diffraction techniques are being used to measure the strains in alumina scales on a variety of high temperature alloys both during oxidation and after cooling to room temperature. The corresponding stresses are being calculated using appropriate elastic constants. The results include the observations that: (1) Growth stresses are higher in alumina formed on FeCrAl alloys as compared to that formed on nickel-base alloys, such as NiAl or single crystal superalloys (studies have not yet been performed on NiCrAl or CoCrAl alloys). (2) Yttrium additions to do not result in lower growth stresses in alumina scales on FeCrAl alloys even though the additions decrease the amount of lateral scale growth. (3) Growth stresses can be relaxed by plastic deformation of both the alloy and oxide. The implications of these results with regard to alumina adhesion are discussed.Publication Metadata only Measurement of residual stresses by X-ray diffraction techniques in MoN and Mo2N coatings deposited by arc PVD on high-speed steel substrate(ELSEVIER SCIENCE SA, 2005) SARIOĞLU, CEVAT; Sarioglu, C; Demirler, U; Kazmanli, MK; Urgen, MPolycrystalline MoN and Mo2N films have promising physical and mechanical properties, which made them candidates for wear- and corrosion-resistant coatings and diffusion barriers in microelectronics. The residual stresses in MoN and Mo2N films consist of thermal and growth stresses or intrinsic stress generated during deposition. Residual stresses in the MoN and Mo2N coatings deposited by arc PVD techniques on HSS substrate were measured by XRD using the Rocking and the Fixed Incidence Multiplane (FIM) techniques. Residual stresses measured by both techniques in Mo2N (face center cubic, f.c.c.) and in MoN (hexagonal) films were about 5 and 10 GPa (compressive), respectively. These results indicated that residual stresses in the MoN film was two times greater than the residual stresses in the Mo2N film. (C) 2004 Elsevier B.V. All rights reserved.Publication Metadata only High-temperature stress measurements during the oxidation of NiAl(Kluwer Academic/Plenum Publ Corp, New York, 2000) SARIOĞLU, CEVAT; Schumann E., Sarioglu C., Blachere J.R., Pettit F.S., Meier G.H.The growth stresses in α-alumina scales growing on stoichiometric NiAl during oxidation in air at 1100 °C have been measured by two X-ray diffraction techniques: the classic rocking technique and a newly developed fixed-incidence multiplane (FIM) technique. The growth stresses were found to be within the experimental uncertainty of the measurements, i.e., near zero. Measurement of the residual stresses using an optical-fluorescence spectroscopy (OFS) technique in adherent regions of the scale, after cooling to room temperature, were consistent with the growth stresses having been negligibly small. These measurements contrast with previous measurements of growth stresses in α-alumina growing on Fe-Cr-Al alloys, using the FIM technique, which indicated compressive growth stresses on the order of 1 GPa. Possible reasons for these differences are discussed.