In this work, a semi-continuous functionally graded material (FGM) between an austenitic and a super duplex stainless steel was obtained. These materials are of great interest for the chemical, offshore, and oil and gas sectors since the austenitic stainless steel type 316L is common (and not so expensive) and super duplex stainless steels have better mechanical and corrosion resistance but are more expensive and complex in their microstructural phases formation and the obtention of the balance between their main phases. Using directed energy deposition, it was possible to efficiently combine two powders of different chemical compositions by automated mixing prior to their delivery into the nozzle, coaxially to the laser beam for melting. A dense material via additive manufacturing was obtained, with minimum defectology and with a semi-continuous and controlled chemical compositional gradient in the manufactured part. The evolution of ferrite formation has been verified and the phase fraction measured. The resulting microstructure, austenite/ferrite ratio, and hardness variations were evaluated, starting from 100% austenitic stainless-steel composition and with variants of 5% in wt.% until achieving 100% of super duplex steel at the end of the part. Finally, the correlation between the increase in hardness of the FGM with the increase in the ferrite phase area fraction was verified.
Nickel-based NiCrSiFeB alloy (Ni-Cr-Si-B self-fluxing family) are excellent candidates for replacing Cobalt-based alloys in aeronautical components such as sealing rings, valve seats, sliding bearing seats, etc. In this type of components, commonly manufactured by centrifugal casting and conventional processes, high temperature wear and stiffness under complex thermo-mechanical stresses cause lack of sealing and an increase in the wear rate. Metal additive manufacturing by direct laser metal deposition with powder (p-LMD) is presented as a potential manufacturing route for the complex processing of this type of alloys. This research work deals with the development of a new manufacturing route using p-LMD that ranges from the proper selection of the chemical composition for the starting powders, the development of the LMD process parameters to tackle the challenges associated to the wide solidification range and crack susceptibility of Ni-Cr-Si-B alloys, its monitoring and control, as well as the post-processing required to achieve the manufacture of aeronautical components. In this work, the porosity analysis, as-built microstructure, hardness at room temperature and at high temperature, and the strengthening mechanisms have been studied in cylinders manufactured with different chemical composition grades and LMD process parameter sets (slow, normal and fast deposition speed).
En el momento de escribir este trabajo, estamos viendo y sufriendo las consecuencias de más de tres meses de guerra en Ucrania, iniciada el 24 de febrero de 2022. Como europeo y español no podía concebir que, tras la Guerra Fría, la postguerra fría y el llamado Nuevo Orden Mundial, de carácter multipolar, con una tendencia creciente a la democratización de los estados, con una nueva agenda internacional con nuevos retos como el cambio climático, la reducción de los armamentos, los problemas demográficos, etc., pudiera estallar una guerra convencional en el Este de Europa. Protagonizada por una de las antiguas superpotencias, Rusia, hoy convertida en una estado autoritario, represor y antioccidental, que ha invadido el territorio de una de sus antigua repúblicas federadas, Ucrania, transformada en una democracia consolidada, abierta a Occidente, europeísta y con un gran progreso económico y social.
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