Search

Bu çalışmada Mg-4Sb-2Al alaşımına, ağırlıkça % 0,5, 1, 2 oranlarında Ce (seryum) elementi ilavesinin etkisi incelenmiştir. Döküm prosesi olarak yüksek basınçlı kokil kalıba döküm yöntemi kullanılmıştır. Üretilmesi planlanan ürünler direk olarak çekme ve darbe numunesi şeklinde üretilmiştir ve çekme numuneleri yarı endüstriyel pilot ölçekli numuneleri temsil etmektedir. Üretilen numunelerin mekanik özelliklerini tespit etmek için çekme deneyleri, sertlik deneyleri, metalurjik ilişkiyi tespit etmek için ise metalografik inceleme, SEM ve XRD incelemeleri yapılmıştır. İlave edilen Ce oranına bağlı olarak mekanik özellikler artmıştır. Bu sonuçlara göre Mg3Sb2, Mg12Ce, CeSb ve Mg fazlarının varlığı tespit edilmiştir. İlave edilen Ce oranının artmasına bağlı olarak yeni bir faz olan CeSb fazının şiddeti artmıştır. CeSb ve Mg3Sb3 intermetalik fazlarının tane sınırlarında biriktiği anlaşılmıştır. Tane sınırlarında çubuğumsu bir şekilde birikim gösteren bu yapılar, dislokasyon hareketini engellemek ve ince taneli bir yapı oluşturmak sureti ile çekme mukavemetini ve sertlik değerlerini artırmıştır. Çekme mukavemeti değerleri %0,5 Ce, %1 Ce, %2 Ce ilave edilen alaşımlar için sırası ile 145-148 MPa, 164-168 MPa, 163-167 MPa aralığında, uzama yüzdeleri ise sırası ile %12, %13 ve %16 olarak tespit edilmiştir. Ce ilavesi ile sertlik değeri 48 BHN’den 54 BHNe’ye artmıştır.

Yüzey özelliklerinin iyileştirilmesinde elektrolit olarak ara-yer elementlerinin kimyasal bağlı olduğu bileşikler saf su içinde çözündürülerek kullanılmıştır. Elektrolitler suda çözünebilen N (azot) ve C (karbon) gibi ara-yer element içeren inorganik tuzlardan seçilmiştir. 3 farklı elektrolit oluşturulmuştur. Birinci elektrolit H2N-CO-NH2, ikincisi NH4NO3 esaslı olarak seçilmiştir. Elektrolit/316 L ara yüzeyinde 300V ve daha yüksek gerilim uygulanarak yüksek enerjili plazma oluşturulmuştur. Yüksek enerjili plazma içinde iyonize olan N ve C elementleri 316L yüzeyine difüze olmuştur. Elektrolitik plazma difüzyon işlemleri, farklı çözeltiler kullanılarak 316 L paslanmaz çelik altlık için gerçekleştirilmiştir. Plazma difüzyon süresi 5 saniye ile 30 dakika arasında seçilmiştir. İşlemler sonucunda yüzeylerin N, C ve O içeren fazlardan oluştuğu, artan süreye bağlı olarak difüzyon mesafesinin ve sertliğin arttığı gözlenmiştir

Surfaces of cam shafts made of AISI 8620 steels were hardened by boriding processes in both solid and liquid mediums. Various chemical agents were used to achieve boride layers on the surfaces of the cam shafts in these processes. It was aimed to examine effects of the chemical agents on microhardness and thickness of the boride layers obtained. It was concluded that a bath composition of 5% B4C-90% SiC-5% KBF4 was appropriate for the hardest and thickest boride layer achieved in the solid medium, and a composition of 70% Na2B4O7-30% B4C in the liquid medium.

Different weight ratios of cerium (0.5, 1 and 2 wt.%) were produced in a controlled atmosphere by High Pressure Die Cast method to Mg-6Al-0.3Mn-1Sn alloy. The influence of cerium on microstructure and high-temperature mechanical properties was investigated. The microstructure study revealed that the main alloy contains intermetallic phases such as alpha-Mg, beta- Mg17Al12, Mg2Sn and Al11Ce3. The hardness values of the alloys were increased with the addition of 0.5%, 1 and 2 cerium. With the addition of 0.5 wt.% Ce, the yield strength increased to 145 MPa. With the addition of 2 wt.% of Ce, it was found to be 160 MPa with an increase of 14%. Tensile strength was obtained as 190 MPa. Elevated temperature tensile test was carried out at 120 degrees C, 180 degrees C and 240 degrees C, to all the alloys. It was found that increased Ce ratio increased the high-temperature mechanical strength. At 120 degrees C, the highest tensile and yield strength values were obtained with 159 MPa and 147 MPa, respectively, in the alloy with 2% wt. cerium added. In the tensile test performed at 180 degrees C, the highest tensile and yield strength were measured as 91 MPa and 77 MPa, respectively. The operating temperature of Mg alloys produced industrially by HPDC has a significant effect on mechanical properties. High operating temperatures reduce mechanical properties. However, the mechanical properties at high test temperatures were increased by the addition of Ce metal to the AM60-1Sn-XCe alloy produced with HPDC.

In the present study, the effect of an La alloying element with different quantities (1, 3 and 5 wt.-%) on the microstructure, mechanical and dry sliding wear properties of Mg- 3Al-3Sn-3Sb alloy was investigated. The wear tests were done on the alloys using pin on-disk equipment against a 4140 steel disc as counterpart under three different sliding velocities of 0.3, 0.6 and 1.2 ms-1 and four different loads of 5, 10, 20 and 40 N. The microstructural results showed that the new intermetallic phases (La5Sn3 and LaSnSb2) were formed with addition of La to the main alloy. Also, it was observed that the hardness of the Mg-3Al-3Sn-3Sb alloy was raised with increasing La addition. Furthermore, the tensile properties of the Mg-3Al-3Sn-3Sb alloy improved with rising La content at room and elevated temperature. The wear rates of the alloys increase with increasing of the sliding speed and load. In addition to this, the wear rate of the Mg-3Al-3Sn-3Sb alloy was found to be higher than that of the La content alloys for all test conditions.

WOS: 000425075700017, The effect of Cerium addition to Mg-5Sn alloy and its influence on the microstructure and mechanical properties of the alloy were investigated in this work. The microstructural investigations indicate that the alloying addition of Ce leads to effective grain refinement. Also, it was observed that adding Ce to the Mg-5Sn alloy results in the formation of new phases in the alloy such as Ce5Sn4 and CeMgSn. These intermetallic phases were considered to be effective on the enhancement of the hardness of Mg-5Sn alloy. Furthermore, the tensile test results at room temperature and elevated temperatures revealed that the yield and tensile strength of the Ce added alloy were higher than those of the base alloy. The elongation was also improved up to 5 wt% Ce addition while higher amounts decreased the elongation both at room and elevated temperatures., Mersin University Scientific Research Project Unit [2016-2-TP2-1928], The authors wish to thank Mersin University Scientific Research Project Unit (grant no.: 2016-2-TP2-1928) for financial support in this study.

In this study the determinations of melt quality was carried out by thermal analysis of ductile iron. The aim of the study was to determine the limits of feederless casting after the determination of inoculation quality in cast iron. Production method of pouring into a sand mold in the entirety and without using feeder systems has been investigated. Forms of the solidification and volume change have been investigated with simulation program as functions of inoculation quality, type of resin in the mold and mold rigidity. Results of the analysis have been compared with the results of experimental iron casting. © 2017, Polish Academy of Sciences. All rights reserved.

Cathodic electrolytic plasma hardening is a novel thermochemical surface modification and hardening process, used to increase wear resistance and surface hardness of metallic components in a local area of interest. The heating efficiency is related with the plasma nozzle design, applied current and electrolyte. The nozzle design is also a critical factor for the hardening of complex shapes, such as gears and camshafts. In this work, lobes of camshafts, fabricated from several cast iron and steel grades were hardened by cathodic electrolytic plasma hardening in aqueous carbonate electrolyte, using a specific plasma nozzle. The camshafts were attached to CNC lathe for turning them in the horizontal axis. In order to optimise heating and to achieve the ideal flowing and wetting by the electrolyte of the lobe case, the ceramic ellipse-shaped nozzle outlet was designed. As a result of preliminary studies, external surface of lobes was heated and subsequently quenched by electrolyte. The hardness of processed surface was in the range of 50-60 HRc for the different camshafts. No distortion was observed on the surface of lobes. Hardness depth was measured to be from 0.1 mm to 5 mm for several lobes. © 2017, Polish Academy of Sciences. All rights reserved., Cumhuriyet Üniversitesi: M582, This work has been supported by the Cumhuriyet University (Cubap-) project Nr. M582.

10th International Conference on Materials Science and Engineering, BraMat 2017 -- 8 March 2017 through 11 March 2017, A sintered material based on pre-alloyed powders (Fe-Ni-Mo) is expansively applied in the automotive industry and Distaloy is today the most widely used raw material worldwide for the production of complex, precise, high strength PM machine parts. In this study a diffusion bonded powder type of Distaloy DC (Fe-2 wt. % Ni-1.5 wt. % Mo, Höganäs-Sweden) was used. It was alloyed by 0.5 and 1 wt. % silicon carbide with the addition of 0.6 wt. % lubricant in the form of introlube®. All the powder mixtures were compacted at 600 MPa, and then sintered for 30 min. in argon atmosphere at 1120° C. After the completed sintering process, the sintered alloy samples were gas-nitrided 1h at 490 °C and 6h at 540 °C, respectively, and cooled slowly to room temperature still under the ammonia atmosphere. The effects of varied amounts of SiC particles on the tribological behavior of nitrided-sintered Distaloy DC composites were investigated. © 2017 Trans Tech Publications, Switzerland.

9Bu calismada, metal-karbon nano-kompozit uretimi hedeflenmistir ve katki malzemesi olarak kullanilacak olan nano-karbon formlari (grafen), elektro eksfoliasyon yontemiyle uretilmistir. Uretilmis olan grafen, alkol ve polimer bazli cozuculerde cozulup, hidrofilik ozellik elde edilmistir takiben metal tozlari bu cozeltiye ilave edilerek homojen bir Grafen-Metal tozu karisimi elde edilmistir. Uretilmis olan bu karisim tozlar direkt olarak tek eksenli pres ve soguk isostatik pres ile pes pese preslenmistir, daha sonra argon ve azot atmosferinde sinterlenmis ve nihai olarak da mikroyapi teksturu, mekanik (sertlik, v.b) ve fiziksel ozellikler (porozite, yogunluk) olculmustur ve karakterizasyon sonuclari tartisilmistir. Ilave edilen ag..%3 Mg ve %1 Zr, Aluminyumun baslangic sertlik degerini 20-30 Hv den 80 HV ye yukselmistir. Artan pres kuvveti ve artan sinterleme sicakligina bagli olarak sertligin 80 HV ve uzeri seviyelerine yukseldigi olculmustur ancak belirli bir degerden sonra mekanik degerlerde azalma oldugu olculmustur. Bu alasima ilave edilen ag.% 0.05, 0.15, 0.3, 0.45 g grafen takviyesi de yine sertlikte ve mukavemette artis saglamistir. Sertlik ve mukavemet degeri sirasi ile 100 HV ve 250 MPa daha ust degerlere uzerine yukselmistir. Grafenin uretimi, kompozit takviye yontemi ve sinterleme sureci ile ilgili sistematik yeni bir yontem elde edilmistir ve bunun sonucunda grafen ilave edilmesinin, matris icinde dolgu etkisi yaparak, mukavemet ve sertlik degerlerinde artisa yol actigi gozlenmistir. Ayrica grafen takviyeli, Al-3Mg-1Zr alasimda asinma direncinin artigi gozlemlenmis ve toz sikistirma surecinde surtunmenin azaldigi ve sikistirilabilirligin arttigi tespit edilmistir. Boyle bir sonucun ozellikle ekstruzyon veya derin cekme gibi islemlerde, sekil verme islemleri sirasinda surtunme kuvvetlerini azaltarak ve deformasyon kabiliyetini artirarak, muhendislik fayda saglayacagina inanilmaktadir.

WOS: 000372383700015, Boronizing of GGG-60 nodular cast iron samples were performed by immersion in molten salts. These were based on borax containing eight reducing agents: Na2CO3, CaCl2, NaCl, NaOH, B4C, SiC, Al and ferrosilicon. Also the cast iron samples were boronized with pack boronizing method using different mixture compositions such as B4C, borax, Na2CO3, and SiC. This work gives a survey on the nature and quality of the layers which were obtained according to the boronizing composition. The effects of the boronizing bath composition on the obtained layers' quality are also discussed. The results of the studies show that the most suitable boronizing compositions for electroless liquid boronizing of GGG-60 cast iron are %65 borax - 25% Fe-Si - 10% NaOH and 70% borax - 30% B4C in order to obtain the hardest and the thickest boride layer. On the other hand, the suggestible composition for pack boronizing of it is 85% B4C - 15% Na2CO3. (C) 2016 Elsevier Ltd. All rights reserved., Scientific and Technological Research Council of Turkey (TUBITAK) [1139B411402970], The study has been supported by The Scientific and Technological Research Council of Turkey (TUBITAK, 1139B411402970)

Micro arc oxidation of wire arc sprayed Al-Mg6, Al-Si12 and Pure Al coatings on low carbon steel has been performed. The coatings have been analyzed using optic microscope, scanning electron microscopy, X-ray diffraction and surface roughness tester. At the same time, voltage and current regimes are investigated during the process. Then after MAO process, uniform Al2O3 ceramic coatings have been deposited on surface of Al-Mg6, Al-Si12 and Al coated steel. The ceramic coatings are mainly composed of Al2O3 phase. The compound coatings show high hardness and significant improvement of corrosion resistance property.

Electrolytic plasma is an emerging, environmentally friendly surface engineering technology that can be used for cleaning of metal surfaces and removing several coating. The present work was concerned with cleaning of corrosion products (oxides and contamination) on steel surfaces for corrosion protection. The e ects of processing parameters on cleaning steel surfaces were investigated. The results show that electrolytic plasma can e ectively produce clean surfaces and remove iron oxides. Also the arc spray coatings deposited on steel was removed by electrolytic plasma.

Plasma electrolysis is an electrolytic-chemical-thermal technique that can be used for local hardening of the difierent type of steels. The feasibility of hardening the 1.2333 cold work tool steel by applying a single-stage-local surface treatment, which combines the methods of plasma electrolysis, is discussed. The effects of treatment dura- tions of plasma electrolytic hardening on the surface microstructural, mechanical, and tribological characteristics of 1.2333 cold work steel substrates are studied. The major advantage of the plasma electrolytic hardening is shown to be hardened layer (maximum 900 Hv-minimum 500 Hv) of the substrates consisting of martensitic phase in very short treatment durations, approximately 7 mm thick/0.5 min. Reciprocating-sliding friction and wear tests against an alumina ball counter face have shown that the application of a plasma electrolysis promotes a change in wear mechanism of the friction pair from relatively severe adhesion-abrasion to mild deformation. This results in simultaneous reduction of the volumetric wear rate from 0.18-0.2 mm3 to 0.04 mm3., Kumruoglu, L.C.; University of Sakarya, Engineering Faculty, Metallurgy and Materials Department, Sakarya, Turkey; email: lkumruoglu@sakarya.edu.tr

High-pressure die casting offers reduced costs due to its small tolerances and smooth surface finish. Casting parts produced are consumed by the automotive industry in millions. In this study, the use of computer aided engineering applications on design of high-pressure die-casting was studied. The influence of casting process steps in die design was studied and analyzed. The casting simulation software was used to improve design and solve problems. By using the simulation software in analyses of die design, the final design was reached in a few hours and thus the design process of pre-production was shortened and mold production was carried out with no revision on die material. Radiographic test was applied on the casting parts and the result shows good correlation between simulations of solidification result data. Also the results proved that the application of squeeze pressure in the intensification phase of high-pressure die casting process could be examined in the casting simulation., Kumruoglu, L.C.; Metallurgical and Materials Engineering Department of University of Sakarya, Esentepe 54187, Turkey; email: lkumru@cumhuriyet.edu.tr

WOS: 000263249700001, In the present study, the mechanical and metallographic properties of camshafts produced from chilled cast iron were examined experimentally and numerically relating with the solidification, cooling rate and metal flow. First of all, with the help of the 3-dimensional drawing and design programs the whole casting methodology was planned. This planning was analyzed with casting simulation software. After that camshafts were produced experimentally at the foundry. Chill material was used in order to get rapid cooling. The phases, dendrite structure and dendrite arm spacing on the lobes of camshaft were examined with an optic microscope and XRD. The Brinell, Rockwell and Vickers hardness tests were carried out on surfaces of lobes and camshafts. On the rapid cooling areas, the ledeburitic phase and high hardness values, on the slow cooling surfaces, rosette like graphite in pearlitic and low ferrite phase and low hardness values were examined. On the chill areas 2-15 mu m DAS (dendrite arm spacing) were measured. (C) 2008 Elsevier Ltd. All rights reserved.

WOS: 000262072800009, Bimetal consisting of stainless steel (316L) and structural steel (30CrNiMo8) was produced by shell mould casting technique and interface region between two metals was characterized by metallographic examination and mechanical tests. Three types of interface occur during the solidification i.e., due to liquid-liquid steel interaction (Interface I), interaction of solid structural steel-liquid stainless steel (Interface II), and solid-solid interaction (Interface III). It is concluded that the Interface I and II have higher microhardness than the Interface III since the interaction region of Interface I and II has mixture of martensitic and bainitic microstructure. As C diffusion takes place from the structural steel to the stainless steel, Cr and Ni diffuse opposite direction of C diffusion. Mechanical properties of the bimetal were greater than that of stainless steel but smaller than that of structural steel. (C) 2008 Elsevier Ltd. All rights reserved.

In this study, 1.2333 cold work tool steel and cast iron (GG 25) were simultaneously melted in di erent furnaces to fabricate composite die mold used in sheet metal forming industry. To enhance the metallurgical bond between two components of composite part, the pouring temperature of cast iron was assessed just above the solidus temperature, then metallurgically prepared cast iron was poured on to the cast tool steel. The temperature and casting parameters were monitored and simulated. Experimental and simulation results were compared, nally the optimum parameters and casting route were revealed.

WOS: 000252514600026, Demands of the metal forming industry made the real time simulation method programs essential for good manufacturing of the finished product. In this paper, the CLF (critical liquid fraction) factor which is necessary for determining whether or not the solidification needs feeder and also where the feeder/feeders is/are needed to be placed is studied. If the value of liquid phase fraction inside a certain region is less than CLF, then liquid cannot pass through this region even under pressure or in the same meaning the feeder does not feed into more depth anymore. This study simulates the CLF factor in a range from 20% to 80% on nodular cast iron castings (GGG50). The solid model formation is considered and discussed with simulation program used. The results showed that by increasing CLF factor, the shrinkage ratio in feeder cavity decreases. (c) 2007 Elsevier B.V. All rights reserved.