Kerim Emre Öksüz

The Effect of Al2O3-SiC and B4 Cadditions on Mechanical Properties of Cusnmatrix Composites for Cutting Tools

Keywords: Boron Carbide; Silisium Carbide; Composite; Powder Metallurgy. Abstract : In this study, effect of boron carbide (B4C), aluminium oxide (Al2O3) and silisium carbide (SiC) addition on microstructure and mechanical properties of diamond cutting segments was investigated. The effects of reinforcement particle additions on characteristic of CuSn matrix composites have been investigated. For this purpose, Al2O3, SiC and B4C addition quantity was added as 2 wt.%. Samples of segments were processed by cold pressing at 550 MPa, followed by sintering at 850°C/30min. Micro-structural aspects were observed by optical microscope. Density, hardness and wear tests were also performed. Wear behaviour and hardness values of segments changed depending on aluminium oxide, silisium carbide and boron carbide addition. The alloy CuSn– 2 wt.%. B4C presented the best results, available for use in cutting tools.

The Influence of Composition and Calcination Temperature on the Phases in (Ba 1- x Sr x Zr)O 3 Perovskites

Several ceramic materials with a perovskite structure often exhibit interesting electronic properties and, therefore, are often called “electroceramics”. Electroceramics with high dielectric constants are used in capacitors and superconductors. The effect on calcination temperatures (1000°C–1400°C) and the changing of ions in A and B sites on the phase formation and microstructure of barium strontium zirconate (Ba1-xSrxZr)O3, BSZ, x = 0.2 and 0.4 ceramics were investigated. The BSZ powders were prepared using the solid state reaction method. The phase purity, crystal structure and microstructure of samples were examined using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD). We found out that the percentage phase purity of perovskite increases with an increase in the calcination temperatures as expected and it was found that BSZ powders adopts a perovskite structure with a cubic () unit cell as well. The purity of perovskite powders was obtained above 1300°C and the purity phase of ceramics was detected in all samples.

Dielectric Properties of Sr-Doped BaZrO 3 Ceramics

Perovskite compounds have received keen interest from academic research due to their unique properties such as ferroelectric, pyroelectric, piezoelectric, and dielectric properties. Nano sized oxides of strontium doped barium zirconate of general formula Ba1-xSrxZrO3 (x= 0.2, 0.4, 0.6, 0.8) have been prepared by a solid-state procedure. The surface morphology, microstructure, and phase analysis, of the sintered ceramics were characterized by field emission scanning electron microscopy (FE-SEM). Scanning electron microscopic studies showed the formation of cubic and hexagonal nanoparticles with an average grain size of 1.6μm±0.47 and 0.82±0.35μm. Dielectric studies were carried out as a function of frequency to explore the electrical properties of Sr-doped BaZrO3.

Effect of SiC Particle Size on the Physical and Mechanical Properties of NiTi Alloys

NiTi shape memory alloys have attracted significant interest due to their unique superelasticity and high damping performance. In this work, the effect of SiC particle size on both physical and mechanical properties of NiTi matrix composite was investigated. Ni and Ti powders with particle sizes of 40 µm were used with the SiC addition with varying particle sizes of 20 µm and 40 µm, respectively. Composites of NiTi with 1wt. % SiC were fabricated by powder metallurgy technique. The effects of SiCp addition on hardness, relative density and wear behavior of NiTi composites have been investigated. The samples were examined by scanning electron microscope, for microstructural studies and phase development. The results showed that the distribution of the reinforced particle was uniform. Moreover, as the SiC particle size decreases, hardness and wear resistance increase. It was demonstrated that SiC particle size significantly enhanced the wear resistance of NiTi composite.

Synthesis and Characterization of CeO 2 Doped ZrO 2 Ceramics by a Simple Sol-Gel Route

It is well known that sol-gel technique is a simple method to produce nano sized ceramic powders. In this study, cerium oxide doped zirconia samples, with 10 mol%-12mol% and14mol% CeO2, were synthesized by sol-gel technique and characterized. The surface morphology, elemental composition, microstructure, and phase analysis, of the sintered CeO2 doped ZrO2 ceramics were characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDS) analysis, and X-ray diffraction (XRD) respectively. X-ray diffraction for samples sintered at 1550 °C for 4h revealed that the zirconia ceramics have a tetragonal phase structure. The addition of CeO2 can raise the content of the tetragonal phase, but the minor monoclinic phase exists even at the CeO2 content of 10 mol%. The effect of dopant concentration on the lattice parameter, average primary crystallite size and micro-strain was studied. Relative densities for CeO2 doped ZrO2 bulk ceramics varied between 95% and 99 %, depending on the CeO2 addition.

Tribological Behavior of Distaloy DC Components

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.

Characterization and Mechanical Properties of PM Fe-Cu/SiCp Alloys

FeCuCo alloys are the new generation of metal matrix for diamonds in PM processed cutting tools. These alloys were created with the purpose of reducing the cobalt content in diamond tools. Nevertheless, little have been published, once this is a matter of industrial interest. In this work, samples of Fe (10-20) wt. %Cu and Fe (10-20) wt. %Cu 1%wt SiCp alloys were processed by cold pressing at 350 MPa, followed by sintering at 1150 C/30 min. under argon atmosphere. After sintering, a study of structural and microstructural analyses was conducted. Brinell hardness and wear tests were carried out in the metal matrix, as well as the wear resistance of the metal matrix composites. The composition Fe-20%wt Cu-1%wt SiCp was the best among the studied ones, because it presented the best results of hardness and wear resistance.