Ahmet Küçük | BAYBURT University (original) (raw)

Papers by Ahmet Küçük

Surface & Coatings Technology, 2001

... They do not have enough inertia required to cross the streamlines in the spray jet, being pro... more ... They do not have enough inertia required to cross the streamlines in the spray jet, being projected to its periphery without depositing on the substrate. ... Thecross-sections of the samples were polished before the indentations. ...

Practical Failure Analysis, 2001

Thermal spray coatings enhance the material properties of substrates but this attribute may be ne... more Thermal spray coatings enhance the material properties of substrates but this attribute may be negated if the coatings themselves fail. This paper investigates the performance of an important family of coatings as one step in improving the resistance of the coating/substrate system to mechanical failure. Thermal barrier coatings of yttria partially stabilized zirconia (YSZ) with a NiCrAlY bond coat were

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2002

Journal of Failure Analysis and Prevention, 2001

Thermal spray coatings enhance the material properties of substrates but this attribute may be ne... more Thermal spray coatings enhance the material properties of substrates but this attribute may be negated if the coatings themselves fail. This paper investigates the performance of an important family of coatings as one step in improving the resistance of the coating/substrate system to mechanical failure. Thermal barrier coatings of yttria partially stabilized zirconia (YSZ) with a NiCrAlY bond coat were air plasma sprayed onto mild-steel substrates. The spray process parameters were varied according to top and bond coat thickness, stand off distance, and substrate temperature. These 17 groups of coating types, with six identical samples in each group, were four point bend tested while coupled with an in-situ acoustic emission transducer. Optical microscopy was then used to examine and map the resulting crack patterns. Measurements of the number of cracks, crack separation, delaminating length, and micro-crack density were also made. The combination of this information, along with properties obtained from the four point bend tests and acoustic emission signals, provided insight into the cracking and delaminating processes.

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2001

... while a thermal spray splat is a microscopic entity that exhibits many nanosized grains highl... more ... while a thermal spray splat is a microscopic entity that exhibits many nanosized grains highly bound among each other. This microstructural difference of nanograined agglomeration rather than a packed structure consisting of nanograins may produce differences in the coating ...

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2000

Journal of Materials Science Letters, 2002

Journal of Materials Engineering and Performance, 2000

Silicate glass and glass-silicon nitride composite coatings were atmospheric plasma sprayed onto ... more Silicate glass and glass-silicon nitride composite coatings were atmospheric plasma sprayed onto mild carbon steel substrates under varying process parameters such as torch power and H2/Ar ratios. The x-ray analysis revealed that Si3N4 in the composite coatings could be preserved under the harsh environmental conditions of the plasma spray process. The presence of Si3N4 as the reinforcement phase to the glass matrix conferred higher hardness properties to the coatings.

Journal of The American Ceramic Society, 2001

Journal of Materials Science, 2001

Journal of Biomedical Materials Research, 2001

The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has aroused as ... more The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has aroused as many controversies as interests over the last decade. Although faster and stronger fixation and more bone growth have been revealed, the performance of HA-coated implants has been doubted. This article will initially address the fundamentals of the material selection, design, and processing of the HA coating and show how the coating microstructure and properties can be a good predictor of the expected behavior in the body. Further discussion will clarify the major concerns with the clinical use of HA coatings and introduce a comprehensive review concerning the outcomes experienced with respect to clinical practice over the past 5 years. A reflection on the results indicates that HA coatings can promote earlier and stronger fixation but exhibit a durability that can be related to the coating quality. Specific relationships between coating quality and clinical performance are being established as characterization methods disclose more information about the coating. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 570–592, 2001

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2000

Journal of The American Ceramic Society, 2001

Yttria-partially-stabilized zirconia was atmospherically plasma sprayed by systematically varying... more Yttria-partially-stabilized zirconia was atmospherically plasma sprayed by systematically varying the process conditions including carrier gas flow rate, torch power, standoff distance, and Ar/H2 ratio in the plasma gas mixture. The in-flight particle parameters such as temperature, velocity, number, and size were determined using a commercially available diagnostic system. The particle parameters were controlled by the particle trajectory in the plume and plasma jet characteristics. The average temperature and the velocity of particles, which reached their maximum at an intermediate carrier gas flow rate of 3.5 L/min, varied as much as 6% and 25%, respectively, with a 75% variation in the carrier gas flow rate by going from the lowest to the intermediate rates. The average temperature and the velocity of particles were lower for a lower torch power, a higher Ar/H2 ratio, and a larger standoff distance. It was necessary to obtain data on particle populations larger than 1000 for statistically reliable and reproducible information from the diagnostic system.

Journal of Biomedical Materials Research, 2001

The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has aroused as ... more The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has aroused as many controversies as interests over the last decade. Although faster and stronger fixation and more bone growth have been revealed, the performance of HA-coated implants has been doubted. This article will initially address the fundamentals of the material selection, design, and processing of the HA coating and show how the coating microstructure and properties can be a good predictor of the expected behavior in the body. Further discussion will clarify the major concerns with the clinical use of HA coatings and introduce a comprehensive review concerning the outcomes experienced with respect to clinical practice over the past 5 years. A reflection on the results indicates that HA coatings can promote earlier and stronger fixation but exhibit a durability that can be related to the coating quality. Specific relationships between coating quality and clinical performance are being established as characterization methods disclose more information about the coating. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 570–592, 2001

Surface & Coatings Technology, 2001

... They do not have enough inertia required to cross the streamlines in the spray jet, being pro... more ... They do not have enough inertia required to cross the streamlines in the spray jet, being projected to its periphery without depositing on the substrate. ... Thecross-sections of the samples were polished before the indentations. ...

Practical Failure Analysis, 2001

Thermal spray coatings enhance the material properties of substrates but this attribute may be ne... more Thermal spray coatings enhance the material properties of substrates but this attribute may be negated if the coatings themselves fail. This paper investigates the performance of an important family of coatings as one step in improving the resistance of the coating/substrate system to mechanical failure. Thermal barrier coatings of yttria partially stabilized zirconia (YSZ) with a NiCrAlY bond coat were

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2002

Journal of Failure Analysis and Prevention, 2001

Thermal spray coatings enhance the material properties of substrates but this attribute may be ne... more Thermal spray coatings enhance the material properties of substrates but this attribute may be negated if the coatings themselves fail. This paper investigates the performance of an important family of coatings as one step in improving the resistance of the coating/substrate system to mechanical failure. Thermal barrier coatings of yttria partially stabilized zirconia (YSZ) with a NiCrAlY bond coat were air plasma sprayed onto mild-steel substrates. The spray process parameters were varied according to top and bond coat thickness, stand off distance, and substrate temperature. These 17 groups of coating types, with six identical samples in each group, were four point bend tested while coupled with an in-situ acoustic emission transducer. Optical microscopy was then used to examine and map the resulting crack patterns. Measurements of the number of cracks, crack separation, delaminating length, and micro-crack density were also made. The combination of this information, along with properties obtained from the four point bend tests and acoustic emission signals, provided insight into the cracking and delaminating processes.

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2001

... while a thermal spray splat is a microscopic entity that exhibits many nanosized grains highl... more ... while a thermal spray splat is a microscopic entity that exhibits many nanosized grains highly bound among each other. This microstructural difference of nanograined agglomeration rather than a packed structure consisting of nanograins may produce differences in the coating ...

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2000

Journal of Materials Science Letters, 2002

Journal of Materials Engineering and Performance, 2000

Silicate glass and glass-silicon nitride composite coatings were atmospheric plasma sprayed onto ... more Silicate glass and glass-silicon nitride composite coatings were atmospheric plasma sprayed onto mild carbon steel substrates under varying process parameters such as torch power and H2/Ar ratios. The x-ray analysis revealed that Si3N4 in the composite coatings could be preserved under the harsh environmental conditions of the plasma spray process. The presence of Si3N4 as the reinforcement phase to the glass matrix conferred higher hardness properties to the coatings.

Journal of The American Ceramic Society, 2001

Journal of Materials Science, 2001

Journal of Biomedical Materials Research, 2001

The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has aroused as ... more The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has aroused as many controversies as interests over the last decade. Although faster and stronger fixation and more bone growth have been revealed, the performance of HA-coated implants has been doubted. This article will initially address the fundamentals of the material selection, design, and processing of the HA coating and show how the coating microstructure and properties can be a good predictor of the expected behavior in the body. Further discussion will clarify the major concerns with the clinical use of HA coatings and introduce a comprehensive review concerning the outcomes experienced with respect to clinical practice over the past 5 years. A reflection on the results indicates that HA coatings can promote earlier and stronger fixation but exhibit a durability that can be related to the coating quality. Specific relationships between coating quality and clinical performance are being established as characterization methods disclose more information about the coating. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 570–592, 2001

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2000

Journal of The American Ceramic Society, 2001

Yttria-partially-stabilized zirconia was atmospherically plasma sprayed by systematically varying... more Yttria-partially-stabilized zirconia was atmospherically plasma sprayed by systematically varying the process conditions including carrier gas flow rate, torch power, standoff distance, and Ar/H2 ratio in the plasma gas mixture. The in-flight particle parameters such as temperature, velocity, number, and size were determined using a commercially available diagnostic system. The particle parameters were controlled by the particle trajectory in the plume and plasma jet characteristics. The average temperature and the velocity of particles, which reached their maximum at an intermediate carrier gas flow rate of 3.5 L/min, varied as much as 6% and 25%, respectively, with a 75% variation in the carrier gas flow rate by going from the lowest to the intermediate rates. The average temperature and the velocity of particles were lower for a lower torch power, a higher Ar/H2 ratio, and a larger standoff distance. It was necessary to obtain data on particle populations larger than 1000 for statistically reliable and reproducible information from the diagnostic system.

Journal of Biomedical Materials Research, 2001

The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has aroused as ... more The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has aroused as many controversies as interests over the last decade. Although faster and stronger fixation and more bone growth have been revealed, the performance of HA-coated implants has been doubted. This article will initially address the fundamentals of the material selection, design, and processing of the HA coating and show how the coating microstructure and properties can be a good predictor of the expected behavior in the body. Further discussion will clarify the major concerns with the clinical use of HA coatings and introduce a comprehensive review concerning the outcomes experienced with respect to clinical practice over the past 5 years. A reflection on the results indicates that HA coatings can promote earlier and stronger fixation but exhibit a durability that can be related to the coating quality. Specific relationships between coating quality and clinical performance are being established as characterization methods disclose more information about the coating. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 570–592, 2001