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Öğe Effect of Double Austenitization and Pre-Annealing Heat Treatment on the Microstructural and Mechanical Properties of QT 41Cr4 Steel(Springer India, 2023) Celtik, Cansu; Ayhan, Ismail Irfan; Yurekturk, YakupIn this study, the effect of double austenitization and pre-annealing heat treatment on the final microstructure concerning changes in hardness, strength, impact toughness and hardenability characteristics of 41Cr4 steel has been examined in comparison with conventional quenching-tempering treatment. The microstructural changes were characterized by an optical microscope (OM) and scanning electron microscope (SEM), and also the variations in austenite grain sizes and carbide sizes were estimated with the Image J program. The results indicated that precursor microstructures formed with quenching and also subcritical annealing tailored the prior austenite grains and carbides in a manner of improving the strength and toughness without loss in hardness and ductility. 776 MPa yield strength and 30 J Charpy impact energy were obtained in conventional quench-tempering settings, and the corresponding values for double austenitization treatment were 886 MPa and 71 J, and 830 MPa and 34 J for pre-annealing treatment, respectively. Grain size reduction and modification of carbides in tempered martensite microstructure with the applied pre-heat treatments resulted in advanced Charpy impact energies including cryogenic test circumstances and room temperature strength values.Öğe Investigation of the effects of hot dip aluminizingand diffusion annealingon microstructural and tribological properties of dual phase (DP800) steels(Pamukkale Univ, 2024) Yurekturk, Yakup; Celtik, CansuIn this study, the effects of hot dip aluminizing (HDA) (90 s at 725 degrees C) and diffusion annealing on the microstructural and tribological properties of DP800 steel were investigated. After HDA treatment, one of the sample was left to cool in air (HDA-1) and the other one left to cool in air after being subjected to a diffusion annealing for 1 hour in an oven set at 300 degrees C (HDA-2). Evolution in mechanical and tribological properties depending on the developments in the coating microstructure investigated in terms of hardness and wear behaviour, respectively. Mechanical characterization results show that diffusion annealing increases the hardness value of hot dip aluminized steel to 1100 HV values. Considering the wear ball volume and friction coefficients, the most advanced tribological properties were observed in the diffusion-annealed HDA process (HDA-2).Öğe MICROSTRUCTURE AND WEAR PROPERTIES OF 42CRMO4 STEEL PREPARED BY VARIOUS HEAT TREATMENTS METHODS(Tanger Ltd, 2022) Celtik, Cansu; Yurekturk, Yakup42CrMo4 steels are widely used in automotive, aerospace applications and machine tools where wear resistance needs to be maintained throughout its lifetime. It is possible to change the initial microstructure of these steels with various heat treatments and improve their mechanical properties. For this purpose, the effect of different heat treatment processes on wear characteristics of 42CrMo4 quality steel was investigated in this study. After various heat treatments methods, spheroidized ferrite-perlite, tempered martensite, tempered martensite with spherical carbides microstructures were obtained in 42CrMo4 steel. Hardness measurements and the wear tests were performed with microhardness tester and reciprocating type tribometer, respectively. The microstructural features developed by the applied heat treatments were examined with an optical microscope, and the wear characteristics were studied in terms of friction coefficient, wear volume loss, and worn surfaces of samples.Öğe Si3N4 reinforced Al-Si-Mg matrix composites: Powder metallurgy fabrication, PEO coating and characterization(Elsevier, 2025) Yurekturk, Yakup; Senyurt, Berk; Celtik, Cansu; Kucukelyas, Burak; Akcamli, NazliSi3N4-reinforced Al-6.5Si-0.5Mg matrix composites were produced via a powder metallurgy (PM) method, which includes high-energy mechanical milling (HEBM) and pressureless sintering. An oxide-based ceramic protective coating was applied to the PM composites using the plasma electrolytic oxidation (PEO) technique. The novel aspect of this study lies in applying a PEO coating on particulate-reinforced AMCs produced through PM, which further enhances the composites' surface properties and corrosion resistance. The microstructural characterizations indicate that the mechanically alloyed (MA'ed) powders comprise Si and Mg phases integrated within the Al matrix along with embedded Si3N4 reinforcement particles, thus ensuring a composite structure. Hence, applying the mechanical alloying (MA) process and Si3N4 incorporation enhanced the densification and hardness properties of the Al-Si-Mg matrix, highlighting its reinforcing effect. The hardness of MA'ed and 15 wt% Si3N4incorporated composite increases to 144 HV. Also, the PEO-coated samples outperform all uncoated samples in terms of corrosion resistance. The PEO-coated Al-6.5Si-0.5Mg-15Si3N4 composite showed an approximate 89% decrease in corrosion rate compared to the uncoated Al-6.5Si-0.5Mg base alloy. Thus, the PEO-coated sample with 15 wt% Si3N4, demonstrates superior performance, with the highest polarization resistance and a balanced charge transfer resistance, making it the most effective in corrosion protection.Öğe Surface characteristics of plasma electrolytic oxidation coatings on Cp-Ti and hot-dip aluminised Cp-Ti(Taylor & Francis Ltd, 2022) Celtik, Cansu; Yurekturk, Yakup; Gecu, Ridvan; Kaboglu, Cihan; Muhaffel, FaizPlasma electrolytic oxidation (PEO) coatings on commercial pure titanium (Cp-Ti) and hot-dip aluminised Cp-Ti surfaces were prepared in an alkaline electrolyte. The morphological, structural, wear, and corrosion characteristics of the coatings were studied by using SEM, EDS, XRD, electrochemical polarisation, and dry sliding wear tests. The experimental results showed that the main compositions of the PEO coating on Cp-Ti are TiO2 and Al2TiO5 phases, while the PEO coating on hot-dip aluminised (HDA'ed) Cp-Ti mainly consists of the Al2O3 phase. The single PEO coating exhibited more porosity with small diameter micro-pores compared to the PEO coating on the HDA'ed sample. Electrochemical polarisation tests revealed that the PEO coating on the HDA'ed sample exhibited approximately 4.6 times more polarisation resistance than the single PEO coating and 10 times that of the bare Cp-Ti sample. According to the wear test results, the wear resistance of the bare Cp-Ti was doubled by hot-dip aluminising (HDA) and PEO treatments, while the single PEO treatment resulted in better resistance against dry sliding wear.
