Papers by Keyword: Fe-Cr Alloys

Abstract: The purpose of this study was to evaluate the chemical and metallurgical aspects, mechanical properties and hardness of the stainless steel of Fe-Cr alloy, the stainless steel of Fe-Cr alloys coating with Ni and Cu-Zn alloys coating with Ni alloys used for microsurgical instruments manufacturing.In dentistry are develop new materials and methods to obtain microsurgical instruments with complex form and who must to present mechanical resistance, good corrosion and a great cleaning identically like the glass. The new methods to obtain the microsurgical instruments try to realize quickly the complex form with a cost is expensive.Ni coating permit a better corrosion resistance of microsurgical instruments, because of the thin shiny layer protective, resistant and homogenous.Ni coating permit a better wear resistance of microsurgical instruments for long time.

Abstract: The aim of this work was to investigate the effect of Cr on the microstructure of neutron-irradiated Fe-Cr alloys. Neutron irradiation-induced damage at its early stage was simulated by ion implantation. Positron Annihilation Spectroscopy was applied to identify irradiation-induced defects depending on the Cr-content in Fe-Cr alloys. Different irradiation scenarios were used to investigate the influences of irradiation step by step.

Abstract: The decomposition of Fe-Cr solid solutions during thermal aging is modeled by Atomistic Kinetic Monte Carlo (AKMC) simulations, using a rigid lattice approximation with composition dependant pair interactions that can reproduce the change of sign of the mixing energy with the alloy composition. The interactions are fitted on ab initio mixing energies and on the experimental phase diagram, as well as on the migration barriers in iron and chromium rich phases. Simulated kinetics is compared with 3D atom probe and neutron scattering experiments.

Abstract: The hardening behavior of precipitation was studied during aging of Fe-Cr alloys. This mechanical behavior is associated with the nanometric modulation structure of the coherent decomposed Fe-rich and Cr-rich phases formed by the spinodal decomposition of the supersaturated solid solution. The growth kinetics of spinodal decomposition was very slow and it increased during coarsening stage. The morphology of decomposed phases consisted of an interconnected irregular shape with no preferential alignment for short aging times and a further aging caused the change to a plate shape of the decomposed Cr-rich phase aligned in the <110> directions of the Fe-rich matrix. The rapid increase in hardness and embrittlement seem to be associated with the coherency and nanometer size of the spinodally-decomposed phases in the aged alloys.

Abstract: The oxidation behaviour of binary Fe-Cr alloys containing 10 and 20 mass % Cr, respectively, was studied in Ar-20%O2, Ar-7%H2O and in Ar-4%H2-7%H2O at temperatures between 800 and 1050°C. Thermogravimetric analyses in combination with analytical studies using SEM/EDX and Raman Spectroscopy revealed, that in atmospheres in which water vapor is the source of oxygen, Cr exhibits a higher tendency to become internally oxidized than in the Ar-O2 gas. Contrary to previous studies which showed the presence of water vapor to affect transport processes in the surface oxide scale, the present results reveal that the presence of water vapor also affects the transport processes in the alloy. The enhanced internal oxidation, which is likely the result of water vapor increasing the solubility and/or the diffusivity of oxygen in the alloy, explains the frequently observed effect that Fe(Ni)Cr alloys with intermediate Cr contents (e.g. 10-20%, depending on temperature) exhibit protective oxidation in dry gases but breakaway type oxidation in steam. The temperature dependence of the change from protective to non-protective behaviour in Ar-H2O differs quantitatively, but not qualitatively from that in Ar-O2.

Abstract: Two boride layers were found to form at the interface of iiron-chromiium alllloys (10 and 25% Cr) or an industrial 13% Cr steel and boron at 850-950 oC and reaction times in the range 1-12 h. In the case of a Fe-10% Cr alloy and the steel, the layers are based on the FeB and Fe2B compounds. With a Fe-25% Cr alloy, the constituent phases are FeB and CrB for the outer layer and Fe2B and Cr2B for the inner layer. Both layers are characterized by a pronounced texture. Diffusional growth kinetics of boride layers are close to parabolic and can alternatively be described by a system of two non-linear differential equations, producing a good fit to the experimental data. The temperature dependence of the layer growth-rate constants obeys a relation of the Arrhenius type.

Abstract: This study is intended to reduce the difference of thermal expansion coefficient between metallic interconnector and solid electrolyte of SOFC (Solid Oxide Fuel Cell) without sacrificing of electrical conductivity. Fe-Cr alloys have been chosen as candidate materials due to its merit of low cost and high temperature oxidation resistance. Different amount of alloys element and compositions have been varied to optimize the properties by method of alloys design with aid of thermodynamics software Thermal-Cal. Phase diagrams of multi-components alloys have been drawn to predict the possible stable phases formed in the investigated metals. An arc melter and plasma melting furnace were used to melt the investigated alloys. The measurements of thermal expansion coefficients and electrical conductivities are carried out with TMA and ASR resistance instrument. The results indicate that the Fe-10Cr alloy exhibits the smallest thermal expansion coefficient among the alloys, while Fe-16Cr has a lowest electrical resistance .