Applied Mechanics and Materials Vols. 752-753

Abstract: The objective of this present research was to study the surface liquid segregation (SLS) of 7075 aluminum alloy formed by semi-solid squeeze casting together with the gas induce semi-solid technique (GISS). The rheocasting times of 3, 5, 10, and 20 seconds, were used in GISS processes. The cross sectional areas of specimens near the mold were used to measure the surface segregation. The results revealed that longer rheocasting time gave higher amount of solid fraction in the semi-solid slurry. In addition, it was found that when solid fraction increased, the surface segregation increased.

Abstract: The effects of Gas Induced Semi-Solid (GISS) in the slurry die casting process on defects of 7075 aluminum alloy were studied, different initial solid fractions with 10, 15, and 20 sec of rheocasting time were investigated. The results showed that the percentage of porosity in semi-solid die casting was smaller than in the liquid die casting. In terms of the initial solid fraction in 7075 aluminum alloy, it was found that the defects were found when the initial solid fraction was high. In addition.

Abstract: In this study, a multi-chamber detonation sprayer (MCDS) was applied for deposition of Co-Cr-Al-Y powder coatings (200-250 mm thick) on nickel base superalloy JS6U (Russia). Powder Co-25Cr-11Al-1Y (d(0.1): 6.6 μm, d(0.5): 62.7 μm, d(0.9): 123,4 μm) was used to deposit of a coatings. The coatings microstructures and phase compositions were characterized using SEM, OM and XRD techniques. Measurement of the microhardness of samples was done with a micro-hardness tester DM – 8B using a Vickers’s indenter with load on of 0.1 N. It was established that MCDS has provided the conditions for formation of a dense layer with porosity 0.05% and microhardness 600±50 HV_0.1.

Abstract: Multi-chamber detonation sprayer (MCDS) was applied for deposition of WC-Co-Cr powder coatings on corrosion-resistant steel. Powder AMPERIT®554.074 WC-Co-Cr was used to deposit of a coatings. The coatings microstructures and phase compositions were characterized using SEM, OM and XRD techniques. Measurement of the microhardness of samples was done with a micro-hardness tester DM – 8B using a Vickers’s indenter with load on of 0.3 N. It was established that MCDS has provided the conditions for formation of a dense layer with porosity of less than 1.5 % and microhardness 750±50 HV_0.3.

Abstract: The ASTM T23 steel with a composition of Fe-2.25Cr-1.6W-0.1Mo in wt.% was corroded in the Na₂SO₄ salt at 800 and at 900°C, and its corrosion behavior was studied. It formed thick, porous oxide scales that consisted primarily of outer Fe-rich oxides and inner (Fe, Cr)-rich oxides. The corrosion of the T23 steel progressed mainly via oxidation.

Abstract: The corrosion behavior of the ASTM T92 steel in the Na₂SO₄ salt was studied at 800 and 900°C. At 800°C, the T92 steel formed thin (Fe, Cr)-rich oxide scales, indicating a good corrosion resistance due to 9%Cr presented in the alloy. However, at 900°C, the T92 steel displayed poor corrosion resistance, because the scales dissolved off rapidly owing to the increased corrosion rate.

Abstract: In order to improve the mechanical properties of the layer deposited by anodic oxidation of aluminum on the material EN AW-1050 H24, in the contribution was investigated the microhardness of the deposited layer as a function of the physic-chemical factors affecting in the process of anodic oxidation at the constant anodic current density J = 3 A.dm^-2 in electrolyte formed by sulfuric acid and oxalic acid, with the emphasis on the influence of electrolyte temperature in the range – 1,78 °C to 45,78 °C. The model of the studied dependence was compiled based on mathematical and statistical analysis of matrix from experimental obtained data from composite rotation plan of experiment with five independent variable factors (amount of sulfuric acid in the electrolyte, the amount of oxalic acid in the electrolyte, electrolyte, anodizing time and applied voltage).

Abstract: SUS 310 stainless steels were corroded at 600, 700 and 800°C for up to 30 h in 1 atm of N₂/H₂O/H₂S-mixed gas. The formed scales consisted primarily of (Fe_0.5Ni_0.5)_0.96S, FeNiS₂, and FeCr₂S₄. They were fragile, porous, and susceptible to spallation. During corrosion, Fe, Ni, and Mn diffused outward, while sulfur and a lesser amount of oxygen diffused inward. The diffusion of Cr and Si was not conspicuous. The formation of sulfide scales and the presence of hydrogen and water vapor in the mixed gases made SUS 310 corrode fast.

Abstract:

The identification of the optimum material of an endodontic prefabricated parallel post (EPPP) is carried out in the current study. The primary goal of the current work is to analyze the effect of post material on the stress distribution surrounding EPPP. Ten different post materials: 1-carbon fibre (CF), 2-gold alloy (GA), 3-titanium alloy (TA), 4-stainless steel (SS), 5-composite resin (CR), 6-fiber reinforced composite (FRFC), 7-carbon (C), 8-glass fiber (GF), 9-zirconia (Z), and 10-ribbond fiber+bonding agent+flowable composite (RBF) are used in the present work. In order to identify the best post material, the stress distribution surrounding EPPP with the previous materials are investigated through finite element analysis (FEA). The results obtained show that, the best material of an EPPP is GF. In this study, in order to identify the optimum material of an EPPP, the optimization technique is adopted. The results obtained show that, the optimum values of elastic modulus (E) and Poisson’s ratio (υ) equal to 63.69 GPa and 0.214115, respectively. These resulting values mean that, the optimum material of an EPPP is borosillicate glass (BG).