New nanostructured Fe-(Nb,Cr)-(C,B) multicomponent alloys have been developed for hardfacing application. They have better wear resistance than traditional Fe-Cr-C alloys. The nanoalpha-Fe, eutectic and hard carboborides phases of the weld metal usually show variations with the welding procedure. 6 test samples with different heat input were welded. It was observed that the percentage of eutectic phase and the distance between carboborides increased for the high heat input. Microhardness of eutectic phases showed a linear relationship with the spacing. Samples with high percentage of alpha-Fe phases showed a severe plastic deformation. Wear resistance was optimal for thinner eutectics phases. The presence of needles carboborides improved wear resistance.

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Este es un artículo publicado en acceso (Open Access) abierto bajo la licencia Creative Commons Attribution NonCommercial, que permite su uso, distribución y reproducción en cualquier medio, sin restricciones siempre que sin fines comerciales y que el trabajo original sea debidamente citado.Recibido: 30 Jun., 2017 Aprobado: 24 Ago., 2017 E-mail: agustingualco@yahoo.com.ar (AG)Resumen: La soldadura de recargue es una temática que viene ganando relevancia en el último tiempo asociada a una gran cantidad de aplicaciones en diversas industrias. Los recargues duros de aceros multicomponentes nanoestructurados, de reciente creación, presentan un conjunto de propiedades sobresalientes. Sin embargo, es escasa la información disponible sobre su procesamiento. El objetivo de este trabajo fue analizar la influencia del calor aportado, sobre la dilución, la evolución microestructural y la dureza de depósitos nanoestructurados base hierro con carburos complejos, del sistema Cr-Mo-W-Nb-C-B-Fe. Se soldaron bajo la configuración "bead on plate", mediante el proceso de soldadura semiautomático FCAW con protección gaseosa, variando el aporte térmico entre 0,5 a 3,5 kJ/mm. Sobre cada cupón soldado se analizó la composición química, se determinó el porcentaje de dilución, se realizó el relevamiento dimensional de los cordones y se caracterizó la microestructura mediante difracción de rayos X y microscopías óptica y electrónica de barrido. Además se midió la microdureza Vickers en la zona central del cordón. Se encontró que la dilución del metal depositado se mantuvo entre 28 y 34%, sin observarse variaciones significativas con el aporte térmico. Se observó una microestructura formada por una matriz -Fe y carburos metálicos complejos. Se pudo ver que el tamaño de los precipitados aumentó con el incremento del calor aportado. La dureza de los cordones aumentó al disminuir el calor aportado, de 800 HV 2 para 3,5 kJ/mm a 970 HV2 para 0,5 kJ/mm.Palabras clave: Recubrimientos duros; FCAW; Materiales nanoestructurados; Calor aportado; Microestructura. Influence of Heat Input on Microstructure in Multicomponents (Cr, Mo, W, Nb, C, B) Fe-Based Nanostructured HardfacingsAbstract: Surfacing welding is an issue that was increasing in relevance in last years, related with a raising number of applications in several industries. Hardfacings of nanostructured multicomponent steel of recent creation, have a set of outstanding properties. Nevertheless, the information available related with its processing is still scarce. The aim of this work was to analyze the influence of heat input on the dilution, microstructure and microhardness of a Fe-based nanostructured alloy with complex carbides. Eight bead on plate samples were welded using heat inputs between 0.5 and 3.5 kJ/mm. The dimensional study was performed as well as chemical composition and percentage of dilution with the base metal were determined and the microstructure was analyzed using optical and electronic microscopy and X-ray diffraction. Microhardness was also measured. It was observed t...

New multi-component alloys have been recently developed for applications in coatings deposited by welding. These microstructures consist on the precipitates of ultra-hard carbo-borides in a matrix with high hardness. Post-weld heat treatment is a relevant aspect to adjusting the final propierties of the deposit. In the present work, the microstructural evolution, phase properties and resistance to abrasive wear of a Fe-Cr-Nb-B-C-Si-Mn alloy deposited on a low carbon steel by semi-automatic welding process were studied. The samples were heat treated for 3 hours at temperatures between 500 and 900 °C. They were compared with respect to the samples "as welded". The microstructure was analized by scanning electron microscopy, X-ray diffraction and transmission electron microscopy. A microstructure formed by tetragonal carboborides M 2 B and niobium carbides, with a microhardness of 1800 HV and 2440 HV, respectively, in a matrix formed by high hardness martensite (870 HV) was observed. The post-weld heat treatment produced the tempering of the martensite and the precipitation of secondary carbides from 500 to 800 °C, producing a decrease in hardness with increasing temperature. In the specimen heat-treated at 900 °C, the hardness increased at 1130 HV, reaching higher values than those obtained in the "welded" condition (940 HV), due to the formation of martensite and M 23 X 6 carbides. A linear relationship was found between hardness and abrasive wear rate.