SEARCH RESULT

Rolling has an important place in iron and steel industry due to the advantages such as production speed, continuity and easy to process applications. Roll materials must be resistant to high heat temperature conditions, high breaking resistance, good surface quality, proper hardness, good wear resistance and thermal shocks. However, producing an alloy material with all of these features together will be very costly. Instead of producing a roll material having all of these properties, it is more economical and practical approach to provide these characteristics by surface modification. In this study, External cooling rollers (ECR) coated by different four techniques which, Flame spray, boriding, titanizing and borotitanizing. After the coating process, the thickness of the coating layer, hardness, and layer structures examined by optic microscope, scanning electron microscope, micro hardness, and X-ray analyses. A wide range of coating thicknesses and microhardness values obtained depending on coating technique. The highest mircohardness obtained in the titanized sample, but the lowest coating thickness. The obtained hardness values were 3 times higher than those in the current application. The cost of rolling will be reduced by increase in ECR tool life.

International Iron & Steel Symposium
UDCS

Mehmet DEMİR Ali GÜNEN Mustafa Serdar KARAKAŞ Vahdettin Koç Mustafa Sabri Gök Ahmet ÇÜRÜK

Titanium (Ti) + Niobium (Ni) doped Interstitial Free (IF) steel grades (Ti + Nb IF steel) are widely used in steel industries because of their good formability properties. In this study, the effect of cold rolling reduction rate on the microstructure and mechanical properties of IF steel was investigated in details. The samples subjected to cold rolling with various reduction rates ranging from 40% to 80% at constant annealed temperature. The changes in microstructure were examined with optical microscope. Mechanical properties such as cupping values, anisotropy values (r) yield strength, tensile strength and elongation. were examined by Erichson and tensile test. The results affects the microstructural evolution and carbide precipitations significantly, in turn altering the mechanical properties. Increasing amount of cold rolling reduction rate resulted for an increase in the cupping values, anisotropy values, yield strength and elongation, whereas it leaded to a decrease in tensile strength. As a result of this trial experiment it can be said that reduction rate has a great effect on mechanical and microstructure properties of Ti+Nb doped IF steel. clearly demonstrated that the reduction rate of cold rolling.

International Iron & Steel Symposium
UDCS

Ali GÜNEN M. Mustafa ERŞEN Erdogan KANCA Murat YILDIZ Mehmet DEMİR Bülent KURT Mustafa Sabri Gök

This paper reviews performance of PVD coated steels under combined wear and corrosion conditions (tribocorrosion behaviour) in sliding contacts exposed to aqueous solutions. Available literature related to this context and the researches emerged on last two decades was especially overviewed. This study also aims to understand coupled interactions between mechanical wear and electrochemical processes. One of the key objectives of this review is to provide an overview on wear and corrosion of engineering coatings of steels. The study also identifies suitable applications for industrial environments and foregrounds additional issues associated with coated surfaces as well as main degradation mechanisms.

International Symposium on Light Alloys and Composite Materials
UHAKS

Sabri Alkan Mustafa Sabri Gök

In this research, adhesive wear behavior of FeCr slag coating in water environment was investigated. FeCr slag coatings, deposited onto AISI 420 stainless steel specimens with atmospheric plasma spray (APS) method, were subjected to adhesive wear tests in aqueous environment using a pin-on-disk tribometer. 7N load, 0,08 m/s sliding speed and 538 m sliding distance were used as sliding wear test parameters. In addition to the SEM analyses of the worn samples, friction coefficient graphs and 3D profilometer measurements were used to evaluate the wear performance of FeCr slag coatings in water environment. Surface wear micrographs of the FeCr slag coating worn under aqueous conditions indicate that, friction induced tribological layer formation is reduced as compared to dry sliding wear test results, and resulting surface cracks led to local spallations. Also, friction coefficient under aqueous conditions was found to be three times lower than the average friction coefficient obtained under dry conditions.

International Conference of Advanced Materials and Manufacturing Technologies
ICAMT

Y. Kucuk Mustafa Sabri Gök Mecit Oge

The milling of carbon fiber reinforced polymers (CFRP) is a challenging process due to the non-homogeneous, anisotropic structure and extreme hardness of this type of material. Tool wear occurring during the machining process and the resulting failure mechanisms including delamination, matrix and fiber breakage have severely adverse effects on surface quality of machined products. Since deterioration of machined surface quality may impair the strength of components, particular importance is attached to this situation especially in aviation industry. As a failure mechanism arising from the machining of the materials, this situation may result in timeless damages on critical components, such that, almost 60 % milled CFRP components are discarded due to delamination-related damages. In this context, investigation of the failure mechanisms resulting from delamination and delamination-related situations arising during the milling of CFRP composites was aimed in the present research.

International Conference of Advanced Materials and Manufacturing Technologies
ICAMT

Dervis Ozkan Mustafa Sabri Gök Hasan GÖKKAYA Abdullah Cahit KARAOGLANLI

In this study, a comparative examination of the effect of sliding speed, as a ball-on-disc sliding wear test parameter, was investigated under aqueous conditions. For this purpose, AISI 420 stainless steel specimens were prepared in cylindrical form (Ø25x8 mm), then they were coated with commercially available ceramic coatings (Cr2O3 and Al2O3) using APS technique. Adhesive wear tests were carried out by the use of a ball-on-disc testing rig. The tests were performed under 7N load, 0.08 m/s and 0.12 m/s sliding speeds. After the wear tests, worn samples were subjected to SEM analysis and profilometer measurements. The effect of sliding speed on wear performance of ceramic coatings was evaluated based on the analysis and measurement results. SEM images of Al2O3 coating indicate that, increasing sliding speed also increased the effect of plastic deformation, further inducing tribological layer formation. SEM images of Cr2O3 coating surface, on the other hand, indicated no significant effect of sliding speed at macro or micro level, which is mainly attributed to the higher hardness of Cr2O3 coating than Al2O3 coating. Friction coefficient graphs of both coatings indicated no significant change at both sliding speeds.

International Conference of Advanced Materials and Manufacturing Technologies
ICAMT

Mustafa Sabri Gök Y. Kucuk Mecit Oge

In the present research on milling of carbon fiber reinforced polymer (CFRPs) composites widely used in aviation industry, the effects of different cutting speeds and feed rates on the surface roughness was investigated using tungsten carbidecobalt based (WC-Co) carbide cutting tools. A CFRP composite with 6 mm thickness and 24 layers was used as the work-piece. The tests were performed on a CNC vertical processing center with 100, 200 and 300 m/min cutting speeds, 0.05-0.15 and 0.25 mm/tooth feed rates and 1 mm constant cutting width under dry conditions. Following the tests, the surface roughness of the work-piece was investigated. 5.7 µm surface roughness was obtained with 100 m/min cutting speed and 0.25 mm/tooth feed rate.

International Conference of Advanced Materials and Manufacturing Technologies
ICAMT

Dervis Ozkan Mustafa Sabri Gök Hasan GÖKKAYA Abdullah Cahit KARAOGLANLI

As a protective coating method initially developed for space and aviation industry thermal spray coating techniques have been widely used in several fields. Among a vast number of thermal spray coating techniques, Atmospheric Plasma Spraying (APS) and High Velocity Oxygen Fuel (HVOF) techniques are widely applied against harsh conditions such as wear, oxidation and corrosion due to their high applicability and cost efficiency. In the present research NiCr coating was deposited on Inconel 718 substrate materials using plasma spray and HVOF methods, and the coated specimens were subjected to dry sliding wear tests under 3, 5, 7 and 10N loads at 0,08 m/s sliding speed using a pin-on-disc tribometer. Characterization of the coated specimens was performed before and after the wear tests using conventional characterization techniques. According to the wear loss and coefficient of friction values obtained after the performed tests, the coatings deposited with HVOF technique exhibited a higher wear performance as compared to those deposited with APS technique.

International Conference of Advanced Materials and Manufacturing Technologies
ICAMT

Mecit Oge Fettullah Yildiz S. Parlakyigit Mustafa Sabri Gök Abdullah Cahit KARAOGLANLI

In this research Al2O3 (Metco 130SF) powder was deposited on AISI 420 stainless streel substrates using Atmosperic Plasma Spray (APS) technique. Wear tests were performed on a ball-on-disc wear testing rig (Turkyus brand) to evaluate the dry and aqueous adhesive wear behaviors of the obtained coatings. Test parameters were specified as 7N load and 0.08 m/s sliding speed. The SEM micrographs of the wear track surface and friction coefficients were used in the analysis of the coating’s wear behavior. Additionally, volumetric mass loss calculations were conducted using a 3D optical profilometer. Friction coefficients were respectively found as 0.7 and 0.35 for dry and aqueous conditions, indicating a nearly 50% reduction in the latter case. The decline in worn volume values was also in proportion with the decline in friction coefficient. The comparison of dry and aqueous environment SEM micrographs show that, tribological layer formation occurred at a reduced level in water, which is attributed to the increase in local heat transfer. Also, surface cracks are more apparent under dry conditions, whereas radial crack formations are observed nearby the edges of the wear track under aqueous conditions.

International Conference of Advanced Materials and Manufacturing Technologies
ICAMT

Y. Kucuk Mustafa Sabri Gök Mecit Oge

In this research, sliding wear behavior of Cr2O3 (Metco 6156) coating, deposited onto AISI 420 specimens prepared in a cylindrical form (Ø25x8 mm) using atmospheric plasma spray (APS) methods, was evaluated in water environment. For this purpose, Cr2O3 powder, obtained from Sulzer Metco with commercial code Metco 6156 was deposited on AISI 420 stainless steel substrates. Wear mechanisms were interpreted using SEM analyses and 3D profilometer measurements of the samples worn in aqueous media. Adhesive wear behaviors of the coating were comparatively evaluated for dry and aqueous conditions using the same test parameters. The average friction coefficient value was found as 0.3 under dry conditions, whereas this value was found to be nearly 30% lower after the tests in water. SEM micrographs of the worn surfaces show that, the effect of plastic deformation was reduced in water. Also, the amount and lengths of the cracks forming on the worn surface were found to be lower than those of dry conditions, and such cracks resulted in fatigue induced de-bonding.

International Conference of Advanced Materials and Manufacturing Technologies
ICAMT

Y. Kucuk Mustafa Sabri Gök Mecit Oge