Hector Javier Vergara Hernández

Tecnológico Nacional de México/Instituto Tecnológico de Morelia · Division of Postgraduate Studies and Research (DEPI).

The kinematics of the wetting front, i.e., the loci of the boundary between stable vapor film and the presence of bubbles, during quenching operations largely determines the evolution of the microstructural and displacement fields which, in turn, control the properties of the quenched product. Thus, it is important to develop techniques that allow...

This study explores the optimization of Resistance Spot Welding (RSW) parameters for joining dissimilar thickness Dual Phase-270 steels. A full factorial design and Taguchi’s method were employed to identify optimal welding parameters maximizing joint strength. Tensile tests and Vickers hardness measurements were conducted to evaluate the mechanica...

Secondary hardening by precipitation of alloy carbides during tempering in an experimental Cr-Mo-V alloy steel was studied under continuous and isothermal conditions. Measurements of microhardness and nanohardness analysed the hardening behaviour during stage IV as a function of time, temperature, and heating rate. Scanning electron microscopy and...

The superficial quality of the strip is a very important issue in steel production. Considering the dimensions, the thickness is one of the most important variables in the production of a strip. In the present study, the elastic curve of Back Up Rolls (BURs) is analyzed, considering them as simply supported beams as well as the effect of rolls on t...

The superficial quality of the strip is a very important issue in steel production; the profile, flat-ness, and geometry of strip are indicators of supreme quality. Considering the dimensions, the thickness is one of the most important variables in the production of strip. In the present study the elastic curve of Back Up Rolls (BUR) is analyzed, c...

The tempering kinetics in a Cr–Mo–V medium-carbon low-alloy martensitic steel was determined by an analytical kinetic model of isochronous conversion and differential dilatometry under non-isothermal conditions. The tempering zone associated with stages II and III, and the degree of tempering was determined by dilatometric analysis and the lever ru...

Nowadays, there is a growing interest in processing of multifunctional components for several industrial applications. These components are designed as a combination of several materials with complementary properties to fulfill different functions. Powder metallurgy is able to produce components with adequate properties. Parts composed of two layer...

Multifunctional materials are of interest for biomedical applications due to the different features they exhibit to improve osseointegration of bone implants. Therefore, this work focuses on the fabrication of a three-layer component by powder metallurgy. Samples are composed of one dense layer, another porous and a composite layer using Ti6Al4V al...

The monitoring of the steel heating process is crucial for ensuring the quality and consistency of the final product as well as for optimizing the manufacturing process and reducing costs. This study explored deep learning for the semantic segmentation task of identifying steel heated to high temperatures using infrared thermography. The 1045 steel...

A physical model was developed to estimate the thermal history in hypoeutectoid steel under continuous cooling and forced convection conditions. The thermal histories were acquired at different cooling rates to emulate the forced-convection conditions in a controlled cooling conveyor and compared in every cooling condition with the microstructural...

Metals’ properties can be enhanced through high-temperature treatments. These treatments can also enhance the mechanical properties of metals, such as strength, hardness, and ductility. This is achieved by altering the microstructure of the metal, which can improve its ability to withstand stress and deformation. To ensure the effectiveness of the...

The present repository includes images, scripts, and steps to process digital metallographs using the depth-measurements script for ImageJ. Image2 or Fiji is required to run the scripts for each stage. The next sections explain the general procedure for preparing images for measurements and a basic statistical analysis using ImageJ commands and sc...

A physical model was developed to estimate the thermal history in hypoeutectoid steel under continuous cooling and forcedconvection conditions. The thermal histories were acquired at different cooling rates to emulate the forced-convection conditions in a controlled cooling conveyor and compared in every cooling condition with the microstructural e...

Ti6Al4V (Ti64) alloy is the most used metal material for bone implants because of its good biocompatibility and adapted mechanical properties. Nevertheless, it shows low antibacterial activity, which may favor its failure. Addition of antibacterial elements such as copper should avoid this drawback. This work studies the addition of Cu into a Ti64...

In the present work, the susceptibility to hydrogen embrittlement under hydrogen pressure was evaluated for an experimental X-120 microalloyed steel with four quenching treatments to determine the effect of hydrogen on the hardness and toughness behaviour, for its use in gas and oil transport. The steel was reheated at 820° and 900 °C and then quen...

The aim of the present work is to evaluate the activation energy (Ea) at different cathodic over-potentials (η) by potentiodynamic tests which were carried out at different temperatures of Ni-based, NiCr-m, and NiCr-p porous electrodes, during the alkaline electrolysis processes. On the other hand, the electrochemical stability of the electrodes wa...

It is obvious to many that metals produce a characteristic sound when struck. It is well known that for centuries people have subtly struck coins to differentiate between real and counterfeit coins. Unfortunately, when the materials present slight differences such as thermal or mechanical treatments, it is almost impossible for the human ear to dif...

Secondary hardeningSecondary hardening generated by the sequential precipitation of alloy carbidesAlloy carbides was studied on a medium-carbon low-alloy Cr–Mo steel during isothermal tempering. TemperingTempering was carried out at 500, 550, and 600 °C at different times: 0, 15, 30, 45, 60, 90, 120, 240, 360, 480, and 600 min from a fully martensi...

The effect of thickness and chemical composition on the electrical power and thermal resistance of dilatometric specimens heated by Joule heating are analyzed in different steels, using stepped tests of constant temperature and electrical current. In the stepped constant temperature tests, the electric current necessary to maintain the target tempe...

n this work, cylindrical steel bars with 0.6%C were instrumented and annealed by forced convection with air at room temperature emulating the industrial conditions for obtaining a medium carbon wire rod. Microstructure in the bars was analyzed by Scanning Electron Microscopy (SEM) and Vickers microhardness, and the thermal histories acquired during...

An alternative methodology is presented to recognize the internal state of a material, which, unlike other methods, it is not necessary to take destructive tests, in addition to the high time and costs involved. The methodology in question is summarized in a technique based on the acoustic-vibrational behaviour of metal alloys, to correlate their a...

Resumen El objetivo de este trabajo es fabricar y caracterizar materiales con dos capas con características y propiedades diferentes. Las capas están formadas de un compuesto de Ti-Co y otra de Ti con gran porosidad inducida mediante el método del espaciador para aplicaciones en implantes óseos. Las muestras fueron fabricadas mediante la ruta de me...

Resumen Los materiales más utilizados para la fabricación de implantes son el acero inoxidable 316L, CoCrMo y Ti6Al4V. Cada uno de ellos posee características que les permiten cumplir de manera aceptable su tarea de remplazar un hueso. Sin embargo, la combinación de dos o más de ellos podría generar un material que ayude a mejorar el desempeño y du...

Eje1. La investigación en las Ciencias Básicas Mesa 1. Ciencias Naturales y de Materiales Palabras Clave: (Nitruración, materiales porosos, dilatometría, DRX) Resumen Los materiales con módulo elástico relativamente alto tales como: 316, CoCrMo y Ti6Al4V usados como implantes a largo plazo (<10 años), pueden provocar apantallamiento de tensiones, f...

Resumen Un compuesto de Ti6Al4V reforzado con partículas de CoCrMo es obtenido mediante pulvimetalurgia convencional y sinterización en estado semi-sólido. Los compuestos se fabrican mezclando diferentes fracciones de volumen de partículas de CoCrMo (10-30 % vol.) como partículas de refuerzo en la matriz de Ti6Al4V. La sinterización se estudia medi...

Resumen Los materiales más utilizados para la fabricación de implantes son el acero inoxidable 316L, CoCrMo y Ti6Al4V. Cada uno de ellos posee características que les permiten cumplir de manera aceptable su tarea de remplazar un hueso. Sin embargo, la combinación de dos o más de ellos podría generar un material que ayude a mejorar el desempeño y du...

This work presents a methodology to produce materials with specific properties by conventional powder metallurgy route. The fabricated component is a dental implant based on Ti6Al4V powders, with different microstructures and properties that will allow a better and faster osseointegration. This component is made of three different layers, an upper...

We present a novel Ti64/20Ag highly porous composite fabricated by powder metallurgy for biomedical applications and provide an insight into its microstructure and mechanical proprieties. In this work, the Ti64/20Ag highly porous composites were successfully fabricated by the space holder technique and consolidated by liquid phase sintering, at low...

El efecto de las condiciones de temple y revenido se estudiaron en un acero experimental de medio carbono y baja aleación Cr-Mo mediante ensayos de permeabilidad de hidrógeno para determinar el efecto de la condición microestructural sobre los tiempos de carga. El tratamiento térmico de temple se llevó a cabo en membranas del acero experimental con...

This research work aimed to determine the hydrogen gas pressure effect on the mechanical properties of an experimental X-120 microalloyed steel, subjected to heat treatments and quenched in different mediums. The steel in its as-received condition was reheated at 900 °C and quenched in spray water (900QSW), pressurized air (900QPA), and emulsion of...

Optical decarburization measurements are preferred for quality tests, modeling, or indirect methods over carbon steel products. The measurements are commonly done by metallographs and can be supported by image processing. Image processing allows the collection of multiple measurements from digital micrographs. Nevertheless, limited attention has be...

Hydrogen permeation tests are carried out to evaluate the effect of the quenching medium and tempering temperature on the permeation parameters and density of hydrogen traps, of a Cr–Mo–V low-alloy medium-carbon steel. Three types of steel membranes are tested: 1) in the as-quenched condition, 2) tempered at 235 °C and 3) tempered at 530 °C; each o...

El presente documento introduce una metodología para la medición de profundidad de capa descarburada en metalografías usando procesamiento de imágenes. La metodología utiliza como base el software ImageJ y funciones de procesamiento del propio software, así como propias. El procesamiento de las imágenes digitales (metalografías) pasa por un preproc...

La invención se refiere a un dispositivo para la medición de la expansión y/o contracción térmica lineal de una probeta metálica cilíndrica hueca de estructura cristalina sometida a un tratamiento térmico. El procedimiento de medición de la probeta de trabajo depende de las rampas de calentamiento y enfriamiento programadas por el usuario a través...

El dispositivo presentado en esta invención mide la expansión y/o contracción térmica lineal de una probeta metálica cilíndrica hueca de estructura cristalina sometida a un calentamiento mediante el efecto Joule. La probeta está montada a un sistema de sujeción que cuenta con un par de mordazas porta-electrodo que permiten realizar el calentamiento...

El dispositivo presentadoen esta invención mide la expamción y/o contracción térmica lineal de una probeta metálica cilíndrica hueca de estructura cristalina sometida a un calentamiento por efecto Joule. La probeta está montada a un sistema de mordazas porta-electrodo que permiten realizar el calentamiento por efecto Joule, al interior de las morda...

Pitting corrosion in stainless steel (SS) is a punctual defect that promotes fatigue and cracks propagation. Martensitic steel of steam turbine is exposed to the thermal cycle of welding, high pressures, and corrosive environments in the heat-affected zone (HAZ). The presence of δ-ferrite in HAZ causes crystalline grain boundaries sensitization and...

This study reported a theoretical-experimental analysis of dissimilar metals duplex stainless steel (DSS) grade 2205 and twinning induced plasticity (TWIP) steel joined. Welded joints were performed in autogenous mode and using filler metal (ER2209) by the pulsed gas tungsten arc welding (GTAW-P) process. Critical weld regions were characterized me...

A non-isothermal transformation model was proposed to determine the austenite formation kinetics in a steel alloyed with 2.6% wt. Si by dilatometric analysis, considering that the nucleation mechanism does not change with the heating rate. From the dilatometric analysis, it was observed that the austenite formation occurs in two stages; critical te...

The austenite formation kinetics of a low–carbon steel under two initial conditions—annealed and cold– rolled (0.08C–1.22Mn–0.73Si) were determined by dilatometric analysis during continuous heating. In both conditions, the austenite formation occurred in two stages. The critical transformation temperatures are a function of the heating rate but no...

High-temperature surface oxidation kinetics were determined for low-carbon steel using a Joule heating device on hollow cylindrical specimens. The growth of the oxide layer was measured in situ between 800 and 1050 ∘C under isothermal oxidation conditions and in an air laboratory atmosphere (O2 = 20.3% and humidity = 42%). Through a laser and infra...

The medium frequency transformer (MFT) with nanocrystalline alloys is quintessential in new DC–DC converters involved in various front-end applications. The center piece to achieve high-performance, efficient MFTs is the core. There are various options of core materials; however, no deep information is available about which material characteristics...

En México hay un incremento en la demanda por aceros para trefilado en frío con un mejor desempeño en sus propiedades mecánicas. Para ello, es necesario tener una homogeneidad microestructural en el espaciado interlaminar de la perlita a través del control de los parámetros en los tratamientos térmicos. Con este fin, probetas cilíndricas de un acer...

Low-carbon steels alloyed with Si and Mn are used in welding electrodes manufacture, due to their ductility, weldability, mechanical resistance, and toughness, all of which depend on microstructure and mechanical properties, associated in turn with austenite decomposition kinetics. Due to this, there is great interest in controlling phase formation...

Microalamabres de Zn − 22%Al − 4%Ag, obtenidos por rolado y trefilado se caracterizaron mediante difracción de Rayos-X (DRX) de manera cualitativa y cuantitativa, a la par se observaron mediante Microscopía Electrónica de Barrido (MEB). Los resultados se compararon con microalambres obtenidos del proceso de solidificación rápida por tambor rotativo...

Hot cracking susceptibility and the formation of brittle martensite phase are the main factors that limit the weldability of a dissimilar joint between carbon steel (CS) and austenitic stainless steel (SS). In this study, the self-constraint finger test was used to correlate the welding thermo-mechanical field with the crack susceptibility of a dis...

Stainless steels are used to manufacture components for the automotive industry, equipment and components of steam turbines for the generation of electrical energy; for this reason, it is important to consider the percentage of martensite and microhardness obtained after applying the arc welding processes. In this paper, specific variations of volt...

This work presents a novel methodology to produce materials with specific properties by powder metallurgy. The fabricated implant prototype, based on Ti6Al4V powders, is composed of three different layers, one with high hardness, a core with large pores and the outer shell with smaller pore size. Interphase bonding was very good, mechanical propert...

A detailed experimental and numerical investigation was performed on a Ti6Al4V/xCoCrMo biomedical composite for bone implant applications. The aim was to understand the effect generated by the addition of different volume fractions of CoCrMo particles on a Ti6Al4V matrix composite processed by powder metallurgy. Distribution of CoCrMo particles ins...

The effect of tempering temperature on the martensite softening in an experimental low-alloy medium carbon steel was studied by dilatometric analysis under isothermal conditions. AISI / SAE 4140 steel was chemically modified by adding molybdenum and vanadium ferroalloys. The experimental steel microstructure was conditioned to determine the temperi...

This work investigates the fabrication of Ti6Al4V/xAg composites processed by powder metallurgy. An atomized Ti6Al4V powder was blended with 0, 5, 10, 15 and 20 vol.% of Ag particles, compacted in a die, and sintered above Ag melting point. The compressibility of the mixtures was analyzed, and the sintering kinetics was evaluated by dilatometry tes...

Steel’s transformation is crucial for quality improvement. The high-temperature reheating process is usually performed under oxidizing atmospheres. Therefore, decarburization is present, resulting in material losses and depreciating the material’s quality. The decarburization depth is commonly used to authenticate the quality of steel or develop pr...

Gas nitriding was used to coat highly porous compacts of Ti6Al4V alloy, and in this work, for the first time, the nitrogen diffusion process was evaluated by means of dilatometry tests. Nitriding was performed between 950 and 1250 °C with a dwell time of 1 h, and the axial deformation was measured during the whole thermal cycle. Coating thickness w...

Hot cracking susceptibility and the formation of brittle martensite phase are the main factors that limit the weldability of a dissimilar joint between carbon steel (CS) and austenitic stainless steel (SS). In this study, the self-constraint finger test was used to correlate the welding thermo-mechanical field with the crack susceptibility of a dis...

The semi-solid sintering of a novel Ti6Al4V/CoCrMo biomedical composite was investigated for the first time by semi-in situ X-ray computed microtomography. Composite was fabricated by dry mixing 15 vol% CoCrMo reinforcing particles with Ti6Al4V particles as matrix. The mixture was poured into a 1 mm diameter quartz capillary. 3D images of the same...

A medium-carbon steel alloyed with vanadium was analyzed by differential dilatometryDilatometry, microhardness and nanoindentationNanoindentation to characterize the fourth temperingTempering stage or secondary hardeningSecondary hardening zone. From isochronal heating paths at different tempering temperatures, the secondary hardeningSecondary hard...

TemperingTemperingkineticsKinetics of the martensite was determined using the Johnson–Mehl–Avrami model in a Cr–Mo–V alloyed medium-carbon steel by dilatometry. Tempering temperatures were determined by non-isothermal analysis at constant heating rate. From these temperatures, isothermal tempering was carried out. The reaction stages were associate...

A microstructural analysis was performed to determine the presence of oxygen in a wire rod section of AISI 1008 steel with a surface mechanical failure produced during wire drawing. The failure zone was analyzed by comparison using three different attack reagents: alkaline sodium chromate (ASC), ASC with hydrogen peroxide and amyl alcohol, and a so...

A coupled thermal-microstructural simulation model was developed to estimate the thermal history in a eutectoid steel wire rod under continuous cooling and forced-convection. The model coupled the phenomena of heat transfer, phase transformation and estimation of the cooling boundary condition. The thermal histories were analyzed at different cooli...

A new processing route is proposed to produce graded porous materials by placing particles of Ti6Al4V with different sizes in different configurations to obtain bilayer samples that can be used as bone implants. The sintering behavior is studied by dilatometry and the effect of the layers’ configuration is established. To determine pore features, S...

The aim of this work was to develop a Ti6Al4V/20CoCrMo−highly porous Ti6Al4V bilayer for biomedical applications. Conventional powder metallurgy technique, with semi-solid state sintering as consolidation step, was employed to fabricate samples with a compact top layer and a porous bottom layer to better mimic natural bone. The densification behavi...

Because of the high demand for dual-phase (DP) steels in the automotive and construction industry, the present investigation focused on evaluating the corrosion resistance of three different commercial DP steels through electrochemical corrosion tests in conventional media (0.5 M NaOH, 3.5 wt.% NaCl, and 0.5 M H2SO4 solution). The potentiodynamic p...

El presente reporte muestra la actualización del comportamiento de los casos reportados como confirmados de COVID–19 por la Secretaría de Salud (SS) de México desde el 23 de marzo, cuando el Laboratorio Nacional SEDEAM inicio el reporte. Día a día se actualizan en el repositorio, con la intensión de monitorear la evolución de la PANDEMIA en nuestro...

Campos 11 de abril del 2020 Introducción El presente reporte muestra la actualización del comportamiento de los casos reportados como confirmados de COVID-19 por la Secretaría de Salud (SS) de México desde el 23 de marzo, cuando el Laboratorio Nacional SEDEAM inicio el reporte. Día a día se actualizan en el repositorio, con la intensión de monitore...

The Martensite decomposition by stages was studied in an experimental medium-carbon Steel alloyed with vanadium under conditions of Continuous heating and differential dilatometry. For the Dilatometric analysis, cylindrical specimens of 5 mm diameter and 15 mm length were machined and heated at different rates: 0.58, 0.75 and 0.91 °C s−1 until reac...

Resumen: La determinación de los parámetros eléctricos y funcionales para aplicación de soldadura requiere realizar pruebas preliminares tanto en la industria como en la investigación. Sin embargo, este proceso resulta ser muy costoso, lento y, para objeto de investigación, de baja confiabilidad, por tal motivo, el desarrollo de una metodología de...

This work shows the influence of the normal anisotropy (“r” value) in the deep drawing of AISI 439 ferritic stainless steel sheets. In order to do so, quantitative chemical analysis, metallographic analysis, tensile mechanical properties, and the determination of the “r” value and the “n” value were carried out in two different AISI 439 steel sheet...

One steel containing 0.6 wt pct C, 0,78 wt pct Mn, and 0.32 wt pct Cr was austenitized at 840 oC for 1 hour and cooled at two rates. Microstructural evaluation by light optical and scanning electron metallography showed a change in the pearlite microstructure. Cooling in air as compared to furnace cooling reduced the pearlite interlamellar spacing...

The influence of the hardening mechanisms by solid-solution and grain size on the ferrite nanohardness was analyzed in a low-carbon steel. A low-carbon steel alloyed was used to determine the effect of the composition on the ferrite nanohardness. The surface of each specimen was polished by vibration with colloidal silica suspension to obtain stres...

In this work, continuous cooling treatments were carried out in steels with 0.75% C, with the aim of characterizing the spheroidal pearlite obtained in slow cooling treatments and its relationship with the ultimate tensile strength (UTS). With the use of Scanning Electron Microscopy, the pearlite interlamellar spacing for each cooling condition was...

The design and fabrication of a bilayer Ti6Al4V–Ti6Al4V/30Ta component were performed by using the powder metallurgy process and solid-state sintering as the consolidation step. Phase change and sintering densification of the component were studied by dilatometry. The addition of 30 vol% of Ta to the Ti6Al4V matrix had a noticeable effect over the...

(EN): The invention relates to a process for preparing a homogeneous zirconium oxide coating on both faces of a steel substrate, imparting thereto the properties of generating hydrogen via alkaline water electrolysis, being more resistant to corrosion and increasing the generation of gas during the alkaline hydrolysis. During this process, the alre...

The invention relates to a process for preparing a homogeneous zirconium oxide coating on both faces of a steel substrate, imparting thereto the properties of generating hydrogen via alkaline water electrolysis, being more resistant to corrosion and increasing the generation of gas during the alkaline hydrolysis. During this process, the already co...