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The modified SAE 10B22 steel has high hardenability, which provides its use in special engineering applications, such as in self-drilling screws, with carbonitrided layer, quenched and tempered. However, these components are susceptible to hydrogen embrittlement, which can cause damage to structural components. In addition, the study of the behavior regarding to hydrogen embrittlement of components with carbonitrided layer has not been done hitherto. In this work the tempering temperature influence on hydrogen embrittlement of modified SAE 10B22 steel, was evaluated after a carbonitriding process. Standard samples and M4 × 50 screws were tested. A galvanostatic circuit was used for hydrogen charging of the samples, which were characterized by low-strain tensile test and the samples fracture were analyzed by SEM. The obtained results demonstrate that by lowering tempering temperatures, the hydrogen-loaded samples presented a greater loss of mechanical properties and greater changes of the micromechanics of fracture. In addition, the geometry of the screw was more prone to the deleterious effects of the hydrogen charging than the conventional specimens. [ABSTRACT FROM AUTHOR]

The API 5CT P110 steel is employed in oil and gas industry due to its excellent mechanical properties. However, its poor corrosion resistance makes necessary the employment of a protection. Although nickel-based and cobalt-based coatings obtained by HVOF have been widely studied regarding corrosion resistance, they are normally associated with other elements. Pure nickel and/or pure cobalt HVOF-obtained coatings have not yet been studied. Therefore, in this work, the corrosion resistance of nickel and cobalt coatings obtained by high-velocity oxy-fuel thermal spraying on API 5CT P110 steel was evaluated. The coatings were characterized regarding morphology and structure by SEM, EDS, XRD, roughness, and Vickers microhardness. The corrosion resistance was evaluated by OCP monitoring and potentiodynamic polarization in a 3.5 wt% sodium chloride solution. The results showed that both coatings acted as a barrier and avoided the contact between the steel substrate and the electrolyte due to the low melting point of the metals employed, which resulted in effective fusion of the particles. Besides, the nickel coating, promoted a better corrosion resistance compared to cobalt coating. [ABSTRACT FROM AUTHOR]