Effect of Gr Contents on Wear Properties of Al2024/MgO/Al2O3/Gr Hybrid Composites

In the present study, hybrid metal matrix composites, Al2024/10Al2O3, Al2024/10Al2O3/3MgO, Al2024/10Al2O3/6MgO, Al2024/10Al2O3/3MgO/1.5 Gr, Al2024/10Al2O3/3MgO/3Gr, and reinforcement samples (AA 2024) produced with powder metallurgy process. AA 2024 and reinforcement powders were determined mixture rations and separately mixed during 30 minutes in a three-dimensional Turbula mixer. The mixed compositions were pressed at 300 MPa and sintered at 550°C during 1 h. After that, three materials were extruded at the same temperature. Experimental results show that hybrid metal matrix composites (HMMCs) a better wear resistance than the reinforcement samples because of higher hardness. Gr behave as a lubricant during wear process. The wear resistance of HMMCs can be optimized with controlling of the reinforcement content and type. © 2018 The Authors

AISI D2 soğuk iş takım çeliğine uygulanan endüstriyel kriyojenik işlemin aşınma davranışları üzerindeki etkisi

In this study, industrial cryogenic process after conventional heat treatment process for various holding time was applied to AISI D2 (DIN 1.2379) cold work tool steel. The effects of the industrial cryogenic process on the wear behavior was investigated. In the wear test 5,10 and 15 N forces were carried out to all group specimens at a constant shear rate (3,16 m/s) and three different wear distances. Experimental results show that cryogenic processing of AISI D2 cold work tool steels have a significant effect on wear behavior. It is determined that the cryogenic process increases the wear resistance of the samples with increasing sliding time. On the other hand, the lowest wear resistance was obtained in the as-cast sample. It has been determined that the wear behavior of the AISI D2 cold work tool steel can be optimized by controlling the cryogenic process parameters

Chill formation on the surface of ductile iron and the effects of austempering heat treatments on microstructures and mechanical properties

Bu çalısmada küresel grafitli dökme demirlerin yüzeyinde çil olusumu ve östemperleme ısıl isleminin mikroyapı ve mekanik özellikler üzerine etkisi incelenmistir. Bu amaçla, numune çapları (Ø10-50 mm), kalıp malzemesi türleri (Kum, Paslanmaz çelik, Çelik ve Bakır) ve et kalınlıkları farklı kalıplara dört farklı kimyasal kompozisyona sahip malzemelerin dökümleri gerçekleştirilmiş ve östemperleme ısıl islemi uygulanmıstır. Deneysel çalısma sonuçları, dökülmüs kosullardaki numunelerde kalıp et kalınlığının sabit tutulduğu ve numune çapının değistiği kosullarda numune çapı büyüdükçe çil derinliğinin azaldığını göstermistir. Bu numunelerde yüzeyden merkeze doğru grafit sayısı azalırken, grafit hacim oranı ve küreselliği artmıs ve özde soğuma hızına bağlı olarak perlitik ya da ferritik yapı olusmustur. Yine dökülmüs kosullardaki numunelerde numune çapının sabit tutulduğu kalıp et kalınlığının değistirildiği kosullarda, kalıp et kalınlığı artıkça yüzeyden merkeze doğru çil derinliği artmıstır. Bu eğilim ısı iletim katsayısı yüksek kalıp malzemesinin kullanılması ile daha belirgin hale gelmistir. Çapı büyük numunelerde (Ø30-50 mm) en yüksek çil derinliği 30 mm numune çapı ve 50 mm et kalınlığına sahip bakır kalıba dökülen numunelerde elde edilmistir. Dökülmüs kosullardaki numunelerde karbür hacim oranı arttıkça aşınma direnci ve çekme dayanımı artarken darbe dayanımı ve toplam uzama azalmıstır. Östemperlenmis kosullardaki I, II ve III nolu alasımlarda çil bölgesinin tamamen çözündüğü, düsük Si ve yüksek Cr içeren IV nolu alasımda ise çil bölgesinin varlığını bir miktar azalarak koruduğu gözlenmistir. Östemperleme ısıl islemi genel olarak darbe, çekme ve toplam uzamayı arttırırken asınma direncini düsürmüstür. Ancak IV. nolu alasımda aşınma direncindeki kayıp çok az gerçekleşmiştir. Yapay sinir ağları (YSA) ile yapılan matematiksel modelden elde edilen değerlerin deneysel sonuçlarla büyük oranda örtüstüğü belirlenmistir.In this study, the effects of chill formation on the surface of ductile iron and austempering heat treatment on microstructure and mechanical properties were investigated. For this aim, the casting of material having four different chemical compositions were carried out to moulds having different samples diameter (Ø10-50 mm), mould material type (Sand, Stainless Steel, Steel and Copper) and mould wall thickness than all sample were austempered. Experimental study results showed that in the as-cast samples, the chill depth decreased with increasing sample diameter when mould wall thickness was constant and sample diameter is variable. In these samples the graphite volüme fraction and the nodularity increased from surface to center and perlitic or ferritic structure was formed depending on the cooling rate. Again, in the ascast samples, the chill depth was increased with increasing the mould Wall thickness on the condition which the sample diameter was constant and the mould wall thickness was variable. This trend became more obvious by using the mould material having high heat transfer coefficient. In the large diameter samples (Ø30-50 mm), the highest chill depth was obtained in the sample having 30 mm diameter and 50 mm wall thickness. The wear resistance increased with increasing carbide volume fraction as impact strength, tensile strength and total elongation reduced in the as-cast samples. It was observed that the chill zone completely dissolved in the alloys of I, II and III at austempered conditions, but the chill zone in the IV. alloy containing low Si and high Cr content preserve its persistence with decreasing to some extend. Generally austempering heat treatments increase the impact strength, tensile strength and total elongation while it decreases wear resistance. It is defined that the value obtained from mathematical model performed with artificial neural network (ANN) is quite similar with experimental results

Abrasive wear behavior of various reinforced AA6061 matrix composites produced with hot pressing process: A comparative study

The effects of various reinforcements (boron carbide -silicon carbide-alumina) with constant volume fraction (20 %) on the abrasive wear properties of AA6061 matrix composites produced with hot pressing process were investigated. The wear tests were carried out using a pin-on-disk wear tester by sliding at sliding speeds of 1.2 m/s against silicon carbide paper. Applied normal loads have 5, 10 and 15 N magnitude at room temperature. The wear morphologies of the worn surfaces were analyzed using a scanning electron microscope in order to examine the wear characteristics and to investigate the wear mechanisms. The effects of reinforcement type on the wear behavior of AA6061 matrix composites were observed. Results exhibited that the optimum wear resistance obtained with the boron carbide reinforced composite parts. All reinforced samples showed better wear resistance compared to as-received samples in all the studied conditions. Scanning electron microscope characterization showed that test specimens have complex combination of wear mechanisms on the worn surface. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinhei

Tribological performance of glass/epoxy composites filled with MWCNTs

The effect of addition of multi-walled carbon nanotubes (MWCNTs) on the wear behaviour of glass/epoxy compo-sites manufactured using the pre-preg method was investi-gated. The MWCNT filling rates were 0.5, 1, and 2 wt.%, and unfilled composite samples were used for comparison. The worn surfaces were characterised by means of scanning electron microscopy for evaluating the wear mechanisms. The experimental results showed that all the composites filled with MWCNTs have a lower wear loss than the un-filled composite sample, and the wear resistance increased with increase in the amount of MWCNTs. It is revealed that the abrasive wear resistance of the glass/epoxy composites is mainly related to the adhesion at the matrix and fibre in-terface. © 2018 Carl Hanser Verlag. All rights reserved

Machinability analysis in drilling glass/epoxy composites with filled MWCNTs

Drilling is the most used machining process in the assemble of Glass/epoxy composites. Material removing leads to damage and delamination in the drilling process. The present paper deals the effect of drill wt.% of multi walled carbon nanotubes (MWCNTs) on the drilling of glass/epoxy composites in term of torque and push-out delamination. Glass/epoxy composites manufactured by using pre-preg method. The filled rates were considered as 0.5, 1 and 2 wt.%. MWCNTs. Also, the unfilled composite samples were used for comparison. Various cutting speeds (40, 50 and 60 m/min) and feed rates (0.075, 0.1 and 0,125 mm/rev) for coated drills were used. The experimental result showed that the machinability properties of glass/epoxy composites samples can be improved with filling MWCNTs. Higher cutting speed and feed rate increase delamination. Push-out more severe than that of peel-up delamination. © 2017 Trans Tech Publications, Switzerland

Effect of Microstructure on Fatigue Strength of Intercritically Austenitized and Austempered Ductile Irons With Dual Matrix Structures

In the present study the fatigue strength of austempered ductile irons with dual matrix structures (ADI with DMS) has been studied for an unalloyed ductile cast iron. For this purpose, specimens were intercritically austenitized (partially austenitized) in two phase region (alpha + gamma) at various temperatures (810 degrees C, 820 degrees C and 830 degrees C) for 20 minutes and then quenched into salt bath held at austempering temperature of 315 degrees C and 375 degrees C for 120 minutes and then air cooled to room temperature to obtain various ausferrite volume fractions and their morphologies. Conventionally austempered specimens (austempered from 900 degrees C) with fully ausferritic matrix and unalloyed as cast specimens having ferrit + pearlite structures were also tested for a comparison. Rotating bending fatigue test were carried out an the experimental results showed that, in ADI with DMS, volume fraction of ausferrite and continuity of ausferritic structure along intercellular boundaries play important role in determining fatigue strength. The fatigue strength of these specimens increases with increasing ausferrite volume fraction. The fatigue strength was correlated with the ausferrite volume fraction and high carbon austenite and its carbon content. Conventionally austempered specimens exhibited much greater fatigue strength than ADI with DMS specimens.WoSScopu

Wear and mechanical properties of Al6061/SiC/B4C hybrid composites produced with powder metallurgy

This study investigates the production of various reinforced and non-reinforced composite materials using powder metallurgy (PM). It presents the new approach into optimize the mechanical properties of hybrid composites (Al-SiC-B4C) produced with powder extrusion process. A16061 powders are used as the matrix material and B4C and SiC powders are used as the reinforcement materials. Matrix and reinforcement materials are mixed in a three-dimensional mixer. The mixtures are then subjected to cold pressing to form metal block samples. Block samples are subjected to hot extrusion in an extrusion mold after being subjected to a sintering process. This produces samples with a cross-sectional area of 25 x 30 mm(2). These extruded samples were subjected to T6 heat treatment. The composite materials produced are examined in terms of density, hardness, transverse rupture strength, tensile strength, and wear resistance. Furthermore, optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and XRD are performed to examine the microstructure, surface fractures, and surface abrasion. In this study, high density A16061/B4C/SiC hybrid composite materials were successfully produced. After extrusion, some micro particles were found to crack. The highest hardness occurred in 12%B4C reinforced composites. The lowest hardness was obtained in A16061 alloy without reinforcement. The highest tensile strength occurred in 12%SiC particle reinforced composite material. The highest wear resistance was obtained for 9%B4C+3%SiC samples due to the hardness of B4C and the good adhesion properties of the matrix and SiC. (C) 2019 The Authors. Published by Elsevier B.V.C1 [Karakoc, Halil] Hacettepe Univ, Dept Mech Program, TR-06935 Ankara, Turkey.[Ovali, Ismail] Pamukkale Univ, Dept Mfg Engn, TR-20160 Denizli, Turkey.[Dundar, Sibel; Citak, Ramazan] Gazi Univ, Dept Met & Mat Engn, TR-06500 Ankara, Turkey

Effect of Gr Contents on Wear Properties of Al2024/MgO/Al2O3/Gr Hybrid Composites

In the present study, hybrid metal matrix composites, Al2024/10Al2O3, Al2024/10Al2O3/3MgO, Al2024/10Al2O3/6MgO, Al2024/10Al2O3/3MgO/1.5 Gr, Al2024/10Al2O3/3MgO/3Gr, and reinforcement samples (AA 2024) produced with powder metallurgy process. AA 2024 and reinforcement powders were determined mixture rations and separately mixed during 30 minutes in a three-dimensional Turbula mixer. The mixed compositions were pressed at 300 MPa and sintered at 550°C during 1 h. After that, three materials were extruded at the same temperature. Experimental results show that hybrid metal matrix composites (HMMCs) a better wear resistance than the reinforcement samples because of higher hardness. Gr behave as a lubricant during wear process. The wear resistance of HMMCs can be optimized with controlling of the reinforcement content and type

Laser treatment of dual matrix structured cast iron surface: Corrosion resistance of surface

Laser gas assisted treatment of dual matrix structured cast iron surface is carried out and the corrosion response of the surface is examined. A carbon film containing 15% SiC particles and remaining 85% carbon are formed at the workpiece surface prior to the laser treatment process. The formation of carbon film enhances the absorption of the incident laser beam and accommodates uniformly the SiC particles at the workpiece surface. Nitrogen at high pressure is used as an assisting gas during the laser treatment process. Metallurgical and morphological changes in the laser treated layer are examined using a scanning electron microscope, energy dispersive spectroscopy, and X-ray diffraction. Electrochemical tests are carried out to measure the corrosion response of the laser treated and untreated workpiece surfaces. It is found that laser treatment results in a dense layer consisting of fine grains, partially dissolved SiC, and nitrogen compounds in the treated region, which improves corrosion resistance of the laser treated workpiece surface. © 2014 Elsevier Ltd