H. Svoboda has been working in the field of metallic materials, particularly in welding technology and materials processing. Their interests are related to the study of the relationship between process-structure-properties, with special emphasis in mechanical, tribological and corrosion behavior of materials processed
This paper analyses the effects of post-welding heat treatment on the tribological response of we... more This paper analyses the effects of post-welding heat treatment on the tribological response of weld metals for hardfacing. Applied load in wear tests was also studied. The deposit was a martensitic steel obtained with a gas metal arc welding metal-cored wire under gas shielding of Ar-2% CO2 and 2 kJ /mm of heat input. Cross sections were obtained from the welded coupon and subjected at 550°C for 2h. These samples, together with the as-welded (AW) specimens, constituted the system under study. Cross sections were also extracted for both conditions for determination of chemical composition, microstructure characterisation, microhardness measurements in addition to friction and metal-metal wear tests in pure sliding at 500, 1250 and 2000 N of applied load. A microstructure composed of martensite and retained austenite was observed for both conditions. The AW sample presented 16% of retained austenite, whereas the heat-treated one presented 8%. Heat-treated coupons showed secondary hardening associated with precipitation phenomena. In the specimens tested at 500 and 1250 N, the wear mechanism was oxidative and the AW specimens presented higher wear resistance and higher friction coefficient. On the contrary, the wear regimen of the samples tested at 2000 N was severe, with the heat-treated ones more wear resistant with a higher friction coefficient.Fil: Gualco, Agustín. Universidad Nacional de Lomas de Zamora. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Svoboda, Hernán Gabriel. Universidad de Buenos Aires. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Surian, Estela Silvia. Universidad Nacional de Lomas de Zamora. Facultad de Ingeniería; Argentina. Universidad Tecnológica Nacional. Facultad Regional San Nicolás; ArgentinaFil: de Vedia, Luis Alberto. Universidad Nacional de San Martín. Instituto Sabato; Argentin
Fil: Zappa Maidana, Norberto Sebastian. Universidad Nacional de Lomas de Zamora; Argentina. Conse... more Fil: Zappa Maidana, Norberto Sebastian. Universidad Nacional de Lomas de Zamora; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Houssay. Instituto de Tecnologias y Ciencias de la Ingenieria "Hilario Fernandez Long". Universidad de Buenos Aires. Facultad de Ingenieria. Instituto de Tecnologias y Ciencias de la Ingenieria ; Argentina
NiCrBSi coatings were produce by Flame Spray on a carbon steel substrate. The “as spray” coatings... more NiCrBSi coatings were produce by Flame Spray on a carbon steel substrate. The “as spray” coatings were refused by means of Pulsed Gas Tungsten Arc Welding (GTAW-P) process, following different patterns and welding procedure, with objective of optimize the coating characteristics and productivity. The patterns evaluated were oscillated triangular (OT) and oscillated sinusoidal (OS). Travel speed and workpiece-electrode distance were also analyzed. On each obtained sample the surface appearance, macro and microstructure on transverse cuts were evaluated, determining penetration, dilution and level of defects, among others features. Microhardness profiles and adherence were also evaluated. The OS pattern show a more uniform profile of the refused thickness, with less dilution with the base material. Travel speed and workpiece-electrode distance have both significant effect on the volume of refused material, affecting dilution and consequently the resultant coating hardness.
In the last few years, several welding consumables have been developed that deposit hard iron-bas... more In the last few years, several welding consumables have been developed that deposit hard iron-based nanostructured alloy coverings with high resistance to abrasive wear. The erosive and abrasive wear resistances are mainly controlled by the chemical composition and the microstructure. In turn, the microstructure of the deposited metal can show variations with the used welding procedure, particularly in relation to the heat input. The operating parameters that define the heat input (voltage, current and welding speed) affect aspects such as bead geometry (wide, penetration and reinforcement) and dilution with the base material. The purpose of this article is to study the effect of heat input on the geometric characteristics of the bead, the dilution and the microstructural evolution of a nanostructured iron-based alloy deposited by FCAW. Several samples with heat input between 0.5 and 3.5 kJ/mm were welded. A dimensional study was carried out for each welded coupon, the chemical composition was analysed and the microstructure was characterized using optical and electronic scanning microscopy and X-ray diffraction. Microhardness, crystallite size and degree of dilution were also measured. Great influence in these conditions in the process was observed about the geometry of the bead. The dilution varied between 30% and 40%; microhardness of the deposit was found between 800 and 870 HV1, and the size of the crystallite varies between 105 and 130 nm, depending on process variables used. The highest hardnesses and the lowest crystallite sizes were obtained with the lowest heat input, associated with a lower dilution.
International Journal of Refractory Metals & Hard Materials, Apr 1, 2020
Abstract The optimization of the tribological properties of the surfaces by means of hardfacing t... more Abstract The optimization of the tribological properties of the surfaces by means of hardfacing techniques has made great progress in the metallurgical field in recent times. Alloys of the Fe-Cr-C and Fe-C-B type present excellent wear performance under severe conditions, where the incorporation of Nb, Mo and W improves the performance of severe abrasive wear. In this context, new semi-automatic welding consumables have been designed that deposit iron base material of high alloy, with complex carboborides of W, Mo and Cr which present very high hardness and resistant to abrasive wear. The purpose of this work was to compare microstructural variations coupons welded with one or two layers, with or without shielding gas. The chemical composition was measured on each coupon, the microstructure was characterized by X-ray diffraction and scanning electron microscopy. Dilution percentage was determined and Vickers microhardness profiles (HV2) were made on the different phases (HV0.025). It was found that the dilution with and without shielding gas were 26% and 19%. The hardness was 960 and 1100 HV2. An increase in hardness was observed in the recrystallized areas, as well as a higher percentage of carboborides in the last bead.
This paper analyses the effects of post-welding heat treatment on the tribological response of we... more This paper analyses the effects of post-welding heat treatment on the tribological response of weld metals for hardfacing. Applied load in wear tests was also studied. The deposit was a martensitic steel obtained with a gas metal arc welding metal-cored wire under gas shielding of Ar-2% CO2 and 2 kJ /mm of heat input. Cross sections were obtained from the welded coupon and subjected at 550°C for 2h. These samples, together with the as-welded (AW) specimens, constituted the system under study. Cross sections were also extracted for both conditions for determination of chemical composition, microstructure characterisation, microhardness measurements in addition to friction and metal-metal wear tests in pure sliding at 500, 1250 and 2000 N of applied load. A microstructure composed of martensite and retained austenite was observed for both conditions. The AW sample presented 16% of retained austenite, whereas the heat-treated one presented 8%. Heat-treated coupons showed secondary hardening associated with precipitation phenomena. In the specimens tested at 500 and 1250 N, the wear mechanism was oxidative and the AW specimens presented higher wear resistance and higher friction coefficient. On the contrary, the wear regimen of the samples tested at 2000 N was severe, with the heat-treated ones more wear resistant with a higher friction coefficient.Fil: Gualco, Agustín. Universidad Nacional de Lomas de Zamora. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Svoboda, Hernán Gabriel. Universidad de Buenos Aires. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Surian, Estela Silvia. Universidad Nacional de Lomas de Zamora. Facultad de Ingeniería; Argentina. Universidad Tecnológica Nacional. Facultad Regional San Nicolás; ArgentinaFil: de Vedia, Luis Alberto. Universidad Nacional de San Martín. Instituto Sabato; Argentin
Fil: Zappa Maidana, Norberto Sebastian. Universidad Nacional de Lomas de Zamora; Argentina. Conse... more Fil: Zappa Maidana, Norberto Sebastian. Universidad Nacional de Lomas de Zamora; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Houssay. Instituto de Tecnologias y Ciencias de la Ingenieria "Hilario Fernandez Long". Universidad de Buenos Aires. Facultad de Ingenieria. Instituto de Tecnologias y Ciencias de la Ingenieria ; Argentina
NiCrBSi coatings were produce by Flame Spray on a carbon steel substrate. The “as spray” coatings... more NiCrBSi coatings were produce by Flame Spray on a carbon steel substrate. The “as spray” coatings were refused by means of Pulsed Gas Tungsten Arc Welding (GTAW-P) process, following different patterns and welding procedure, with objective of optimize the coating characteristics and productivity. The patterns evaluated were oscillated triangular (OT) and oscillated sinusoidal (OS). Travel speed and workpiece-electrode distance were also analyzed. On each obtained sample the surface appearance, macro and microstructure on transverse cuts were evaluated, determining penetration, dilution and level of defects, among others features. Microhardness profiles and adherence were also evaluated. The OS pattern show a more uniform profile of the refused thickness, with less dilution with the base material. Travel speed and workpiece-electrode distance have both significant effect on the volume of refused material, affecting dilution and consequently the resultant coating hardness.
In the last few years, several welding consumables have been developed that deposit hard iron-bas... more In the last few years, several welding consumables have been developed that deposit hard iron-based nanostructured alloy coverings with high resistance to abrasive wear. The erosive and abrasive wear resistances are mainly controlled by the chemical composition and the microstructure. In turn, the microstructure of the deposited metal can show variations with the used welding procedure, particularly in relation to the heat input. The operating parameters that define the heat input (voltage, current and welding speed) affect aspects such as bead geometry (wide, penetration and reinforcement) and dilution with the base material. The purpose of this article is to study the effect of heat input on the geometric characteristics of the bead, the dilution and the microstructural evolution of a nanostructured iron-based alloy deposited by FCAW. Several samples with heat input between 0.5 and 3.5 kJ/mm were welded. A dimensional study was carried out for each welded coupon, the chemical composition was analysed and the microstructure was characterized using optical and electronic scanning microscopy and X-ray diffraction. Microhardness, crystallite size and degree of dilution were also measured. Great influence in these conditions in the process was observed about the geometry of the bead. The dilution varied between 30% and 40%; microhardness of the deposit was found between 800 and 870 HV1, and the size of the crystallite varies between 105 and 130 nm, depending on process variables used. The highest hardnesses and the lowest crystallite sizes were obtained with the lowest heat input, associated with a lower dilution.
International Journal of Refractory Metals & Hard Materials, Apr 1, 2020
Abstract The optimization of the tribological properties of the surfaces by means of hardfacing t... more Abstract The optimization of the tribological properties of the surfaces by means of hardfacing techniques has made great progress in the metallurgical field in recent times. Alloys of the Fe-Cr-C and Fe-C-B type present excellent wear performance under severe conditions, where the incorporation of Nb, Mo and W improves the performance of severe abrasive wear. In this context, new semi-automatic welding consumables have been designed that deposit iron base material of high alloy, with complex carboborides of W, Mo and Cr which present very high hardness and resistant to abrasive wear. The purpose of this work was to compare microstructural variations coupons welded with one or two layers, with or without shielding gas. The chemical composition was measured on each coupon, the microstructure was characterized by X-ray diffraction and scanning electron microscopy. Dilution percentage was determined and Vickers microhardness profiles (HV2) were made on the different phases (HV0.025). It was found that the dilution with and without shielding gas were 26% and 19%. The hardness was 960 and 1100 HV2. An increase in hardness was observed in the recrystallized areas, as well as a higher percentage of carboborides in the last bead.
La arqueometría en Argentina y Latinoamérica, S. Bertolino, G. R. Cattaneo, A. D. Izeta y G. Castellano (eds.), pp. 265-271., 2010
"Presentamos los resultados de la caracterización morfológica y microestructural –por metalografí... more "Presentamos los resultados de la caracterización morfológica y microestructural –por metalografía y análisis químicos– de un ancla hallada en cercanías del naufragio de la corbeta de guerra HMS Swift (1763-1770), Puerto Deseado. Determinamos algunos aspectos del proceso de fabricación y del material empleado. Las características de la pieza son consistentes con la tecnología de las anclas inglesas del siglo XVIII. En función de estos resultados, analizamos su posible filiación con el sitio Swift.
Palabras clave: Ancla – Siglo XVIII – Arqueometría – Metalografía – Análisis químico"
Actas del XI Congreso Iberoamericano de Metalurgia (IBEROMET XI) and X Congreso Internacional de Metalurgia y Materiales (CONAMET/SAM), 2010
El Comandante Luis Piedrabuena, destacado navegante de los mares del sur argentino, naufragó el 1... more El Comandante Luis Piedrabuena, destacado navegante de los mares del sur argentino, naufragó el 10 de marzo de 1873 con su goleta Espora en Caleta Lacroix (Bahía Franklin, Isla de los Estados). En apenas 57 días, don Luis construyó una embarcación (cúter) de 12 metros de eslora y 18 toneladas, con la que se hizo nuevamente a la mar. La llamó Luisito, en homenaje a su hijo. Su construcción, inmersa en esos parajes deshabitados, con muy pocos hombres y ninguna infraestructura, fue una verdadera hazaña técnica. Con esta pequeña nave no sólo logró volver al continente, sino que además siguió navegando durante varios años. Este marino unía a sus dotes de navegante una probada habilidad como carpintero, diseñador naval y metalurgista, de la cual muy poco se ha hablado. En el presente trabajo se estudiaron restos de clavos recuperados del maderamen de un naufragio hallado en la zona intermareal de Bahía Franklin, que fue identificado como el Espora. Sobre las muestras obtenidas se realizó la caracterización dimensional, química y microestructural, mediante microscopía óptica (LM), microscopía electrónica de barrido (SEM/EDS) y mediciones de microdureza (HV). Ambos clavos fueron realizados con un latón alfa (Cu-Zn) y bajo contenido del Sn. La microestructura de los mismos corresponde a una estructura de solidificación, propia de un proceso de fundición, con presencia de macro y microrechupes. A se vez, se detectó descincificación y bandas de deslizamiento en la zona de la punta. Las características de las piezas son consistentes con la tecnología de los clavos utilizados en el forro de madera del casco de las embarcaciones durante el siglo XIX.
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Papers by HERNAN GABRIEL SVOBODA
Palabras clave: Ancla – Siglo XVIII – Arqueometría – Metalografía – Análisis químico"