10 publications from this institution
In this study, new mold and modified secondary cooling scenario were applied at continuous casting part of a steel factory in Turkey to attain higher mold lifetime and good product quality with reduced process failures. In order to see the influence of these applications, a significant number of casting trials were performed in the factory to produce square steel billets. After finishing the casting, solidification and cooling of steel billets, the examinations were made to check whether the quality faults were formed or not on the products. A significant increase in productivity, quality and the mold lifetime were reached at the high-speed casting between 3.0 and 4.0 m/min for steel billet of 150x150 mm dimensions with the help of modifications made in both primary and secondary cooling zones. For the peritectic grade steels, higher casting speed and much lower breakouts were recorded compared to the old mold.
No abstract is provided for this article.
No abstract is provided for this article.
This study aimed to produce hybrid composites with a AA2024 matrix reinforced by TiC/B 4 C/nano-graphite through a microwave-assisted sintering technique at 560 °C for 60 min. The nano-graphite ratio in the produced composite samples was kept constant as 1 wt.%. TiC and B 4 C were used in equal ratios at 2, 6 and 10 % by weight total to determine their effects on tribological properties. Wear tests were conducted under three different loads: 3, 5 and 10 N. In the hybrid composites produced, an inverse correlation was observed between the increase in reinforcement ratio and sinterability, while a direct correlation relationship was found in hardness and wear resistance. Compared to the sample containing 2 % TiC/B 4 C in total by weight, a ∼50 % increase in Brinell hardness and a 52–68 % decrease in wear rate was obtained in the sample containing 10 % TiC/B 4 C. As the reinforcement ratio increased, tribofilm formation increased, and abrasive wear was replaced by mild-oxidative wear type.
Light magnesium nanocomposites, offering great weight savings, have a great potential to be utilized in aerospace and automotive industries. They have also been attracted much attention to be evaluated as biomaterial recently owing to their in vitro biodegradability and biocompatibility properties. In the present research, the Mg3Zn/TiB2-CNT nanocomposites were successfully manufactured using mechanical alloying, cold compaction at 600 MPa and finally sintering at 560 °C for 1 h. Their microstructural, mechanical, wear and corrosion properties were investigated extensively for comparison with the Mg3Zn alloy. It was found that the microhardness of the Mg3Zn nanocomposites increased directly with the hybrid reinforcement ratio. In parallel to the hardness, an addition of 15 vol % TiB2-CNT reinforcement to the Mg3Zn alloy allowed to the improvement of the compressive strength by of 46.3 % at a reasonable ductility level of ∼7.8 % compared to the Mg3Zn alloy. The crystallite size, decreasing with an augmentation in the reinforcement content steadily, was obtained to be smaller than 100 nm for the bulk Mg3Zn nanocomposites. Moreover, the wear loss of Mg3Zn alloy reduced by ∼45 % upon the incorporation of 15 % hybrid reinforcement due to the occurrence of a stable tribolayer between the working couple. An additional benefit of the incorporation of hybrid reinforcement into Mg3Zn alloy was also obtained in the progress of corrosion resistance significantly. The corrosion rate was recorded to be 1462.6 mpy for Mg3Zn but it decreased to 276 mpy upon the incorporation of 10 % hybrid reinforcement into the alloy.
In this paper, the welding quality of API 5L X60 steel pipes was investigated after the application of three different welding scenarios by applying submerged arc welding (SMAW), tungsten inert gas (TIG) and hybrid (TIG + SMAW) welding methods with an average heat input of ca. 1 kJ mm −1 for all passes. For this purpose, the ultrasonic and radiographic tests were done to detect possible discontinuities such as crack and porosity in the welding zones. In addition, the macro and microstructures of weld zones were made to examine different zones in terms of weld quality and phases. Moreover, the hardness, impact toughness and tensile tests were carried out to determine the mechanical properties of the weldments. The tensile strength of the pipe weldments was recorded to be ∼603, 610 and 625 MPa after the welding of pipes by SMAW, TIG + SMAW and TIG welding, respectively. In addition, the impact toughness of the welds was obtained to be 48, 76 and 66 J, for these welding methods, successively. According to the experimental findings, all three welding plans were successfully applied to the steel pipes and found to be suitable regarding the relevant international standards.
In the study, the effects of hybrid reinforcement (nano-alumina and MWCNT) and heat treatment on the wear behavior of the Al–4Cu nanocomposites were investigated under dry sliding condition against W–6Co ball by means of a ball-on-disk type tribometer. The load and the sliding speed were kept constant and selected to be 10 N and 0.1 m s −1 , respectively, in the course of the wear tests. Meanwhile, the wear tests were completed after a total sliding distance of 1500 m was reached for each case. During these tests, the wear loss of the nanocomposites was measured at every 250 m. The worn surfaces of the nanocomposites were examined with the help of stereo and scanning electron microscopes. The volumetric wear rates, wear coefficients and wear mechanisms were identified for the nanocomposites to clarify the influence of reinforcement content and heat treatment on their wear resistance. The volume loss at the wear distance of 1500 m was obtained as 24.9 and 8.2 mm 3 for the annealed and aged Al–4Cu alloy, respectively. On the other hand, it decreased to 4.6 and 3.2 mm 3 in the case of the nanocomposites with 15% hybrid reinforcement in the annealed and aged conditions, successively. Moreover, increasing the hybrid reinforcement amount decreased the wear loss of the aged nanocomposites substantially in such a way that it resulted in the mild wear.
In this study, B 4 C and SiC hybrid reinforced Al–Cu–Mg–Si alloy Matrix composites were fabricated using a microwave sintering technique at a sintering temperature of 550 °C for 60 min. In the produced hybrid composites, while the B 4 C ratio was kept constant (3 wt%), SiC was used in four different amounts (3, 6, 9, and 12 wt%). In these produced hybrid composites, as a result of microwave sintering, thanks to the high microwave absorption of SiC, the porosities closed at a rate of 36.65–40.90%. In 3, 6, 9, and 12 wt% SiC reinforced composites, the microhardness of 100.1, 106.8, 114.4, and 117.2 HV 0.05 were achieved, respectively. Due to agglomeration increasing with SiC reinforcement rate, delamination wears increased in 12 wt% SiC reinforced hybrid composite. As a result, the lowest specific wear rate was measured as 0.3374 × 10 −3 mm 3 ·(Nm) −1 in the 3 wt% B 4 C+9 wt% SiC reinforced sample.
In this study, AISI 1040 and AISI 4140 steels were boriding using Ekabor-II commercial boriding powder with powder-pack boriding method using microwave and conventional heating methods. The samples were borided at 950 °C for 2 and 6 hours in an Ar atmosphere in a microwave oven of Enerzi-Mh2912-V8. Biphasic structure (FeB/Fe2B) was formed in all borided AISI 4140 samples and AISI 1040 samples borided for 6 hours. A single-phase structure was observed in AISI 1040 steel borided for 2 hours. Compared to the conventional method, a 1.5-1.6 times thicker boride layer was obtained in AISI 4140 and AISI 1040 steels with microwave-assisted powder-pack boriding. The highest hardness was measured as 1561.8 HV0.05 for boriding AISI 4140 steel and 1499.7 HV0.05 for boriding AISI 1040 steel. The Vickers indentation fracture toughness of borided steels with microwave energy varied between 2.31 and 3.46 MPa·m1/2. It was determined that in all samples borided by the microwave-assisted and conventional powder-pack boriding method, the adhesion strength between the boride layers and the substrate obtained was sufficient.
The study aimed to improve the hardness, wear, and corrosion resistance of powder metal AISI 316 stainless steel alloy using boro-sintering to form FeB and Fe2B compounds on the sample surface at different temperatures and durations utilizing Ekabor II boriding powder. The boride layer thickness was measured, and boron diffusion kinetics were determined. The boron diffusion activation energy was computed at 190.29 kJ·mol-1 during boro-sintering. The microhardness test revealed 12.5 times increase in the hardness of the AISI 316 stainless steel substrate. Adhesion tests using Daimler-Benz Rockwell C confirmed adequate substrate-coating adhesion of the formed boride layers. The ball-on-disc method results indicated that the wear resistance of boro-sintered samples exceeded that of unboronized AISI 316 stainless steel by a ratio ranging from 8.32 to 14.17. Corrosion tests of boronized powder metal AISI 316 stainless steel alloy samples were conducted in 3.5 % NaCl solution, demonstrating a 50 % reduction in corrosion rate with the boro-sintering process.
