Okan Unal | Karabuk University (original) (raw)
Address: Demir Celik Kampusu, 78050, Karabuk, Turkey.
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Papers by Okan Unal
Journal of Mineral, Metal and Material Engineering, 2016
Applied Surface Science, 2015
ABSTRACT Air blast conventional shot peening (CSP), severe shot peening (SSP) and repeening (RP) ... more ABSTRACT Air blast conventional shot peening (CSP), severe shot peening (SSP) and repeening (RP) as a severe plastic deformation applications on AISI 304 austenitic stainless steel is addressed. Shot peened specimens are investigated based on optical, FESEM and digital microscope. The investigations present the austenite transformation to metastable martensite via mechanical twinning due to plastic deformation with high strain rates. It is found that SSP induces thicker nanograin layer with compared to CSP. In XRD studies, the austenite peaks broaden by means of severe shot peening and FWHM increase reveals the grain size reduction below 25 nm regimes on the surface. In EDAX line analysis of CSP specimen, carbon content increase has been detected from deformed layer through the nanocrystalline layer then the content reduces. The carbon segregation takes place due to the energy level distinction between dislocations and Fesingle bondC bonds. 3d contour digital microscope studies and roughness investigations reveal that SSP has deleterious side effect on the surface roughness and surface flatness. However, RP is an effective way to reduce the surface roughness to reasonable values.
Materials Research Innovations, 2013
ABSTRACT In this study, the shot peening process which is a mechanical surface treatment was appl... more ABSTRACT In this study, the shot peening process which is a mechanical surface treatment was applied to AISI 1017 low carbon steel material. The free ball micro abrasion test was applied to the specimens following the peening process. The applied shot peening conditions expose the specimens to higher plastic deformation than traditional shot peening and the aimwas to establish fine grain structures on the surface and right underneath the surface. Conventional characterization techniques, such as optical microscopy, scanning electron microscopy and transmission electron microscopy were used to study the microstructure of the fine-grained layer. Microhardness measurements were also performed across the fine grained layer. As a result of the microstructure studies, it was observed that dislocation was extended as a result of plastic deformation in a layer of size 40 mmon the surface of the specimen. It was observed that the hardness and stiffness of the specimen surface increased due to the peening intensity, and the wear durability increased as a result.
Applied Surface Science, 2014
Journal of Mineral, Metal and Material Engineering, 2016
Applied Surface Science, 2015
ABSTRACT Air blast conventional shot peening (CSP), severe shot peening (SSP) and repeening (RP) ... more ABSTRACT Air blast conventional shot peening (CSP), severe shot peening (SSP) and repeening (RP) as a severe plastic deformation applications on AISI 304 austenitic stainless steel is addressed. Shot peened specimens are investigated based on optical, FESEM and digital microscope. The investigations present the austenite transformation to metastable martensite via mechanical twinning due to plastic deformation with high strain rates. It is found that SSP induces thicker nanograin layer with compared to CSP. In XRD studies, the austenite peaks broaden by means of severe shot peening and FWHM increase reveals the grain size reduction below 25 nm regimes on the surface. In EDAX line analysis of CSP specimen, carbon content increase has been detected from deformed layer through the nanocrystalline layer then the content reduces. The carbon segregation takes place due to the energy level distinction between dislocations and Fesingle bondC bonds. 3d contour digital microscope studies and roughness investigations reveal that SSP has deleterious side effect on the surface roughness and surface flatness. However, RP is an effective way to reduce the surface roughness to reasonable values.
Materials Research Innovations, 2013
ABSTRACT In this study, the shot peening process which is a mechanical surface treatment was appl... more ABSTRACT In this study, the shot peening process which is a mechanical surface treatment was applied to AISI 1017 low carbon steel material. The free ball micro abrasion test was applied to the specimens following the peening process. The applied shot peening conditions expose the specimens to higher plastic deformation than traditional shot peening and the aimwas to establish fine grain structures on the surface and right underneath the surface. Conventional characterization techniques, such as optical microscopy, scanning electron microscopy and transmission electron microscopy were used to study the microstructure of the fine-grained layer. Microhardness measurements were also performed across the fine grained layer. As a result of the microstructure studies, it was observed that dislocation was extended as a result of plastic deformation in a layer of size 40 mmon the surface of the specimen. It was observed that the hardness and stiffness of the specimen surface increased due to the peening intensity, and the wear durability increased as a result.
Applied Surface Science, 2014