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Maraging steels are martensitic steels hardened by precipitation of intermetallic compounds in thermal aging, with good machining properties and high strength, fracture toughness and corrosion resistance, being used in aircraft parts and rocket motor-case, tooling applications and nuclear plants. During thermal aging in steam atmosphere a protective and corrosion resistant oxide layer is formed over the bulk. In this work, conventional Bragg-Brentano geometry was used to identify the phases formed in four specimens of maraging steel grade 300 with different surface finishes that were previously solution annealed twice at (950 ± 5) °C for 1 h, air-cooled, and submitted to oxidation process under positive pressure about 1.5 kPa of steam at (480 ± 5) °C for 6 h, followed by forced air-cooling. Diffraction patterns were measured employing CuKα radiation, ranging 20º < 2θ < 85º and the Rietveld method was used to better characterize the structures identified. Through Rietveld refinements it was possible to conclude that the layer formed during heat treatment process is constituted by a transition metallic phase with a quasi-cubic face centered unit cell, and an oxide layer that includes hematite, magnetite and a spinel structure type MFe2O4, where M could be an alloying element, for all analyzed samples.

Maraging steels are martensitic steels hardened by precipitation during thermal aging, with good machining properties and high strength and corrosion resistance. It is well suited for applications which require high strength-to-weight material, being used in aerospace, aeronautics and nuclear industries. A protective and corrosion resistant oxide layer can be formed during age hardening if treated in steam atmosphere. This work aims to use grazing incidence X-ray diffraction (GIXRD) to evaluate qualitatively the thickness of the layers formed during this process. GIXRD and scanning electron microscopy (SEM) were employed to identify and order the layered structure formed on four specimens of maraging steel grade 300 with different surface finishes that were previously solution annealed twice at (950 ± 5) °C for 1 h, air-cooled, and submitted to oxidation process under positive pressure around 1.5 kPa of steam at (480 ± 5) °C for 6 h followed by forced air cooling. The diffraction patterns were measured employing CuKα radiation and parallel beam, in step scan mode, using incident angles varying from 0.2º to 4.0º and 20º < 2θ < 85º. The results revealed the formation of two layers, the innermost was formed by γ-iron (austenite – fcc) phase followed by a mixture of oxides (hematite and magnetite) on the top, regardless of surface finish, which was confirmed by the SEM analysis that also allowed the measurement of the average layer’s thickness of oxides (1.130 ± 0.094) µm and austenite (0.507 ± 0.090) µm phases, and corroborated the qualitative thicknesses analysis made from GIXRD results.

In this paper we review the new information and communication technologies (ICT), defining what are Learning Objects (LO) and how they have been used in teaching physics. Also reviewed the work of Vygotsky seeking indications of his educational theory to investigate the applicability of learning activities in teaching Physics that use OA in high school. We developed a survey instrument designed for teachers of high school to evaluate its effective use in Brazilian public and private schools and the functional limitations identified by them when they use these computing resources. Based on the literature, and under a vygotskian perspective, we apply some activities with pre-selected LO and evaluated with other research instrument the student's opinions about their use for teaching physics. Our study could support the good acceptance from the students with respect to their use, as reported in the literature and also by teachers, but showed that in addition to limitations of the LO's use, especially of computer simulations, highlighted in the literature and related to cognitive limitations that they can bring when used indiscriminately, there are deeper problems of functional nature that have limited the spread of its effective use by teaching staff.