Serkan Islak

Characterization of hot pressed CuAl–TiC composites with different TiC grain sizes

In this study, the CuAl–TiC composite materials were produced using hot pressing process. Effect of TiC grain size (0.2, 4 and 20 μm) on some properties of these materials was investigated experimentally. Production of CuAl–TiC composites was carried out under pressure of 35 MPa, at 700°C, and for a sintering time of 5 minutes. SEM-MAP studies showed that the TiC grains were relatively homogeneously distributed in the CuAl matrix. Microstructure analysis revealed that the composite materials consist of Cu, Al, Cu9Al4, CuAl2 and TiC phases. With the decreasing of TiC grain size, the hardness, transverse rupture strength, relative density and sintered density of composites increased.

Wear Characteristics of Circular cBN/Diamond Saws Produced by Hot Pressing

Abstract This study describes the investigation of wear characteristics of circular cBN/diamond saws produced by hot pressing. In order to determine the usability of cBN instead of diamond, cBN and diamond grains were added to the bronze matrix. Production of the saws was performed at a sintering temperature of 600–700 °C for a sintering time of 3 minutes. Sawing tests were carried out to determine the wear characteristics of the saws by sawing natural stone. It is concluded that cBN together with diamond could be added to the matrix with a concentration of 12 (the rest of concentration of 30 is diamond) and that the saws will have more wear if this concentration is exceeded. After sawing, SEM analyses of the saws indicate that there were more fractures and wear in cBN grains in comparison to the diamond grains. The results concluded that cBN can be used to saw softer natural stones, or can be added to the matrix together with diamond.

Microstructure and Microhardness Characterization of Cr 3 C 2 -SiC Coatings Produced by the Plasma Transferred Arc Method

Abstract The purpose of this work was to investigate the coatings made of Cr3 C2 and SiC powder manufactured on AISI 304 stainless steel applied by the plasma transferred arc (PTA) welding process. SiC content in the produced coated layer was varied between 0–100 wt.% and the effect of SiC concentration on the microstructure and hardness of the coating was measured experimentally. SEM analyses revealed that the composite coatings had a homogeneous, nonporous, and crack-free microstructure. Dendrites and interdendrite eutectics formed on the coating layer, subject to the temperature gradient and the solidification ratio. There was a significant increase in the hardness of coating layers with the effect of the γ -(Fe,Ni), Cr7 C3, Cr23 C6, Fe5 C2, Cr3 Si, CrSi2, Fe>0.64 Ni0.36, CFe15.1, C-(Fe,Cr)-Si phases formed in the microstructure. In comparison to the substrate, the microhardness of the coatings produced by PTA were 2.5–3.5 times harder.

ESTIMATION OF MECHANICAL AND PHYSICAL PROPERTIES OF Cu-TiC COMPOSITES BY ARTIFICIAL NEURAL NETWORKS (ANN)MODEL

This study aims to estimate the mechanical and physical properties of Cu-TiC composites produced by hot pressing technique using artificial neural networks (ANN) model. The values of relative density, hardness, electrical conductivity, transverse rupture strength, and friction coefficient and wear rate were selected as the output values while the amount of titanium carbide added to copper matrix was selected as the input parameter. The amount of TiC in training data entries is 0, 1, 3, 5, 10 and 15 wt. %. After these values were trained, the output values of copper composites with 2, 4, 6, 8, 12 and 14 wt. % TiC contents were estimated. All estimates show that the regression values are very close to 1. This shows that the ANN model output is very close to the actual data.

TRD YÖNTEMİYLE SUPAP ÇELİĞİ YÜZEYİNDE ÜRETİLEN KAPLAMALARIN MİKROYAPI VE AŞINMA ÖZELLİKLERİ

Bu calismada, kullanim yeri itibariyle surekli asinmaya maruz kalan supaplarin Termoreaktif Difuzyon (TRD) teknigi kullanilarak karisik nitrur esasli kaplamalarla ile kaplanmasi ve mikroyapi ozelliklerinin incelenmesi gerceklestirilmistir. Bu amacla, supap yuzeyine once nitrurasyon islemi uygulanmistir ve sonra TRD yontemiyle supap yuzeyine bor gecistirilmistir. Uretilen kaplamalarin mikroyapi ve faz bilesimi incelemesi, taramali elektron mikroskobu (SEM), X-isin difraktogrami (XRD), X isini enerji dagilim spektrometresi (EDS) ile yapilmistir. Kaplamalarin sertlikleri vikers olarak olculmustur. Kaplamalarin asinma davranisi, tum numunelere ayni kosullarda uygulanan ball on disk asinma testleri yapilarak karsilastirilmistir. Kaplamalarin surtunme katsayilari nispeten dusuk cikmistir.

Yüksek Hızlı Oksi Yakıt ile Üretilen WCCo-Mo Esaslı Kaplamaların Mikroyapı Karakterizasyonu

Bu calisma, yuksek hizli oksi yakit (HVOF) isil puskurtme yontemi ile SAE 4140 celigi uzerinde uretilen WCCo-Mo kompozit kaplamalarin mikroyapisal ozelliklerini arastirmak icin yapilmistir. Bu amac icin WCCo tozlarina ilave edilen Mo miktari % ag. 10, 20, 30 ve 40 olarak degistirilmistir. Kaplamalar, faz bilesimi, mikroyapi ve sertlik ozellikleri acisindan karsilastirilmistir. Kaplama tabakalarinin faz bilesimi ve mikroyapisi X-isini difraktogrami (XRD) ve taramali elektron mikroskobu (SEM) ile incelenmistir. XRD sonuclari, WCCo-Mo kaplama tabakasinin WC, W2C, Co3W3C, Mo2C, MoO2, Mo ve Co fazlardan olustugunu gostermistir. Kaplamalarin sertligi Mo artisi ile artmistir. The present study has been carried out in order to investigate the microstructural properties of WCCo-Mo composite coatings deposited onto a SAE 4140 steel substrate by high velocity oxygen fuel (HVOF) thermal spray. For this purpose, the Mo quantity added to the WCCo was changed as 10, 20, 30 and 40 wt. % percents. The coatings are compared in terms of their phase composition, microstructure and hardness. Phase compound and microstructure of coating layers were examined using X-ray diffractometer (XRD) and scanning electron microscope (SEM). XRD results showed that WCCo-Mo composite coatings were mainly composed of WC, W2C, Co3W3C, Mo2C, MoO2, Mo and Co phases. The average hardness of the coatings increased with increasing Mo content. Anahtar kelimeler: Mo, WCCo, HVOF, Mikroyapi, Sertlik

Effect of sintering temperature on transverse rupture strength of hot pressed Cu-TiC composites

Abstract In this study, effect of sintering temperature on transverse rupture strength (TRS) of Cu-TiC composites produced using hot pressing (HP) technique has been studied. Copper matrix composites reinforced with 10 wt.-% TiC particles were produced under a pressure of 50 MPa, at 600, 700 and 800 °C, and for a sintering time of 4 minutes, respectively. The TRS of the composites were determined using three-point bending test. SEM was used to analyze the fractured surfaces of composites. SEM results showed that with increasing sintering temperature, pores and gaps in the fractured surfaces decreased. The ultimate transverse rupture strength of Cu-TiC composites was found to increase with increasing sintering temperature.

Effect of boron carbide on the microstructure and the mechanical properties of segments produced using hot pressing method

In this study, effect of boron carbide (B4C) addition on microstructure and mechanical properties of diamond cutting segments was investigated. For this purpose, the boron carbide addition quantity was changed as 2, 5 and 10 wt%. In all of the experiments, hot pressing process was carried out at 35 MPa, at 700°C and sintering time of 3 min. Microstructure and phase composition of segments were determined by Scanning Electron Microscopy, Energy Dispersive Spectroscopy (SEM/EDS) and X-ray diffraction (XRD) analysis. Hardness and bending strength values were measured by hardness and three-point bending test devices, respectively. Hardness and bending strength values of segments changed depending on boron carbide rate.