Kaplan, Emine Boynueğri; Şüküroğlu, Süleyman; Şüküroğlu, Ebru Emine

This study focuses on enhancing the surface properties and minimizing the mechanical incompatibility between the AZ91 magnesium alloy and the coating by applying CrAlYN/CrYN gradient coatings through the HiPIMS-PVD method, combined with the enlargement of a MgO intermediate layer via the Micro Arc Oxidation (MAO) method. The duplex coating approach was designed to strengthen adhesion and structural integrity between the substrate and the coating. Coating parameters for both MAO and HiPIMS-PVD processes were optimized using a Taguchi L4 orthogonal array, and the coatings were analyzed using SEM, EDS, XRD and scratch testing. MAO coatings exhibited porous and rough surfaces with volcanic morphologies. The best adhesion performance under MAO conditions was achieved with 650 V, 700 Hz, and a Type B solution, resulting in a critical load value of Lc₂ = 24 N. CrAlYN/CrYN gradient coatings alone showed coating thicknesses from 0.83 μm to 1.66 μm with compact and homogeneous microstructures. Adhesive strength was relatively low (Lc₂ = 5–10 N). In the duplex coating configuration, CrAlYN/CrYN coatings were deposited on the MAO-formed MgO layer, significantly increasing adhesion. Critical load values (Lc₂) ranged from 90 to 110 N, with the highest adhesion achieved under low CrY target voltage and current conditions. The findings demonstrate that the MAO/HiPIMS-PVD duplex coating method substantially improves adhesion and surface characteristics of AZ91 alloy, offering a promising solution for advanced surface engineering applications.

Kaya, Selim

This work presents an analysis of the effect of BaO incorporation on the gamma-ray attenuation properties of systematically evaluated SiO₂-B₂O₃-SrO-ZrO₂ glass matrices. Radiation shielding parameters determined using XCOM and EGS4 calculation codes were compared. There was an increase in glass density from 5.84 g/cm3 to 6.32 g/cm3 when the BaO content rose from roughly 10% to 40%. Using sophisticated WinXCom and EGS-4 calculations, the mass attenuation values (µ/ρ) of BaO doped SiO₂-B₂O₃-SrO-ZrO₂ glass systems (abbreviated BaSiBSZ) were found. This study systematically and thoroughly evaluated the effect of BaO integration on the radiation shielding capabilities of the glass system over a wide range of gamma-ray photon energies, specifically between 59.5 keV and 1332 keV. Initially, HVL (half-value layer) and MFP (mean free path) values were derived from the calculated mass attenuation coefficients. The evaluation of several crucial shielding parameters, including RPE, Zeff, ΣR, and kγ, came next. The steady reduction of SrO oxide concentration and substitution of BaO in BaSiSBZ glass systems resulted in notable modifications in radiation protection properties. The BaSiBSZ glass systems showed a similar decrease in both HVL and MFP at a constant energy level as the BaO doping concentration was progressively raised. Concurrently, a notable enhancement was noted in RPE, Zeff, ΣR, and kγ coefficients. The results demonstrate that higher BaO concentrations greatly enhance the material's radiation-shielding capabilities, enhancing both photon and neutron attenuation and bolstering the overall performance of the glass system.