Respuesta mecánica bajo solicitaciones de contacto esférico en aceros recubiertos

In recent years hard coatings have acquired a significant importance in the microstructural and micromechanical design of forming tools. Among the wide range of surface modification techniques, physical and chemical vapour deposition are the most suitable routes to meet the demanding requirements of...

Descripción completa

Detalles Bibliográficos
Autor: Ramírez Sandoval, Giselle
Tipo de recurso: tesis doctoral
Estado:Versión publicada
Fecha de publicación:2012
País:España
Institución:CBUC, CESCA
Repositorio:TDR. Tesis Doctorales en Red
OAI Identifier:oai:www.tdx.cat:10803/96672
Acceso en línea:http://hdl.handle.net/10803/96672
https://dx.doi.org/10.5821/dissertation-2117-94674
Access Level:acceso abierto
Palabra clave:620
id ES_8f30cdd0f67cb55c2fcf7a47966e2ea6
oai_identifier_str oai:www.tdx.cat:10803/96672
network_acronym_str ES
network_name_str España
repository_id_str
dc.title.none.fl_str_mv Respuesta mecánica bajo solicitaciones de contacto esférico en aceros recubiertos
title Respuesta mecánica bajo solicitaciones de contacto esférico en aceros recubiertos
spellingShingle Respuesta mecánica bajo solicitaciones de contacto esférico en aceros recubiertos
Ramírez Sandoval, Giselle
620
title_short Respuesta mecánica bajo solicitaciones de contacto esférico en aceros recubiertos
title_full Respuesta mecánica bajo solicitaciones de contacto esférico en aceros recubiertos
title_fullStr Respuesta mecánica bajo solicitaciones de contacto esférico en aceros recubiertos
title_full_unstemmed Respuesta mecánica bajo solicitaciones de contacto esférico en aceros recubiertos
title_sort Respuesta mecánica bajo solicitaciones de contacto esférico en aceros recubiertos
dc.creator.none.fl_str_mv Ramírez Sandoval, Giselle
author Ramírez Sandoval, Giselle
author_facet Ramírez Sandoval, Giselle
author_role author
dc.contributor.none.fl_str_mv Llanes, L. M. (Luis Miguel)
Universitat Politècnica de Catalunya. Departament de Ciència dels Materials i Enginyeria Metal·lúrgica
dc.subject.none.fl_str_mv 620
topic 620
description In recent years hard coatings have acquired a significant importance in the microstructural and micromechanical design of forming tools. Among the wide range of surface modification techniques, physical and chemical vapour deposition are the most suitable routes to meet the demanding requirements of surface finish and dimensional tolerances that need some specific tools, such as those for the automotive sector. However, although thin films tend to reduce the impact of tribological service conditions, improved resistance against contact fatigue failure still remains a challenge in the forming tools. The latter has been emphasized in drawing, die cutting and punching processes, where the introduction of advanced high strength steels requires higher impact pressures than those used in conventional metal sheets. In those cases, the load is mainly supported by the substrate. Thus, if any subsurface damage occurs in coated tools, then a premature detachment of the layer could be produced accelerating the wear damage mechanism. However, standardized experimental techniques designed to evaluate the contact fatigue behaviour of coated systems are scarce. Following the above ideas, the aim of the present work was to conduct a systematic study of the contact response and damage mechanisms, under both monotonic and cyclic loading, of conventional thin films deposited onto cold-work tool steels. In doing so, the spherical indentation technique was used to simulate a typical ¿blunt¿ in-service condition and to identify damage evolution associated with increasing load or number of cycles using a small dimension size of samples. Experimental procedure was based on determining critical applied loads and pressures for emergence and evolution of distinct damage modes: circumferential cracking, cohesive spallation and interfacial decohesion. The materials were selected following the criteria of coated systems currently used or potentially applicable as forming tools in industry. The study was divided into two parts: 1) substrate used as a variable to determine the influence of three microstructurally distinct cold work tool steels (1.2379, Universal and HWS); and then 2) coating employed as a variable selecting hard coatings such as TiN and TiC, and a low friction coating such as W-C:H. Experimental results showed that microstructural characteristics of the substrate as well as chemical and mechanical properties of the coating have an important influence in the overall coated system behavior. Concerning substrate influence, differences are clearly evidenced by considering coating detachment under contact fatigue as the critical damage mechanism, specifically for a TiN coating deposited by PVD. On the other hand, conventional scratch tests and even tests under monotonic spherical indentation, were not able to discriminate differences on the mechanical response of the three coated steels studied. In this regard, microstructural effects at the substrate level were rationalized on the basis of crack nucleation resistance of the existing primary carbides as the main reason for the distinct adhesive fatigue response observed. Hence, the optimum intrinsic strength/toughness of primary carbides in HWS and Universal steels as well as their finer and more regular morphology, as compared to the 1.2379 steel, were suggested as key factors for the improved contact fatigue strength exhibited by their corresponding coated systems. This was particularly true for the PM tool steel, where adhesive fatigue failure was completely suppressed as a consequence of their finer and homogeneously distributed primary carbides. Regarding coating properties, droplets were discerned to be detrimental seeds for crack nucleation and cohesive failure at the film surface. Delamination resistance of TiN deposited on a steel substrate Universal under cyclic contact loads increased significantly by using a process of low-pressure chemical vapour deposition.
publishDate 2012
dc.date.none.fl_str_mv 2012
2012
2012
dc.type.none.fl_str_mv info:eu-repo/semantics/doctoralThesis
info:eu-repo/semantics/publishedVersion
format doctoralThesis
status_str publishedVersion
dc.identifier.none.fl_str_mv http://hdl.handle.net/10803/96672
https://dx.doi.org/10.5821/dissertation-2117-94674
url http://hdl.handle.net/10803/96672
https://dx.doi.org/10.5821/dissertation-2117-94674
dc.language.none.fl_str_mv Español
language_invalid_str_mv Español
dc.rights.none.fl_str_mv http://creativecommons.org/licenses/by-nc/3.0/es/
info:eu-repo/semantics/openAccess
rights_invalid_str_mv http://creativecommons.org/licenses/by-nc/3.0/es/
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv 287 p.
application/pdf
application/pdf
dc.publisher.none.fl_str_mv Universitat Politècnica de Catalunya
publisher.none.fl_str_mv Universitat Politècnica de Catalunya
dc.source.none.fl_str_mv TDX (Tesis Doctorals en Xarxa)
reponame:TDR. Tesis Doctorales en Red
instname:CBUC, CESCA
instname_str CBUC, CESCA
reponame_str TDR. Tesis Doctorales en Red
collection TDR. Tesis Doctorales en Red
repository.name.fl_str_mv
repository.mail.fl_str_mv
_version_ 1869413191279181824
spelling Respuesta mecánica bajo solicitaciones de contacto esférico en aceros recubiertosRamírez Sandoval, Giselle620In recent years hard coatings have acquired a significant importance in the microstructural and micromechanical design of forming tools. Among the wide range of surface modification techniques, physical and chemical vapour deposition are the most suitable routes to meet the demanding requirements of surface finish and dimensional tolerances that need some specific tools, such as those for the automotive sector. However, although thin films tend to reduce the impact of tribological service conditions, improved resistance against contact fatigue failure still remains a challenge in the forming tools. The latter has been emphasized in drawing, die cutting and punching processes, where the introduction of advanced high strength steels requires higher impact pressures than those used in conventional metal sheets. In those cases, the load is mainly supported by the substrate. Thus, if any subsurface damage occurs in coated tools, then a premature detachment of the layer could be produced accelerating the wear damage mechanism. However, standardized experimental techniques designed to evaluate the contact fatigue behaviour of coated systems are scarce. Following the above ideas, the aim of the present work was to conduct a systematic study of the contact response and damage mechanisms, under both monotonic and cyclic loading, of conventional thin films deposited onto cold-work tool steels. In doing so, the spherical indentation technique was used to simulate a typical ¿blunt¿ in-service condition and to identify damage evolution associated with increasing load or number of cycles using a small dimension size of samples. Experimental procedure was based on determining critical applied loads and pressures for emergence and evolution of distinct damage modes: circumferential cracking, cohesive spallation and interfacial decohesion. The materials were selected following the criteria of coated systems currently used or potentially applicable as forming tools in industry. The study was divided into two parts: 1) substrate used as a variable to determine the influence of three microstructurally distinct cold work tool steels (1.2379, Universal and HWS); and then 2) coating employed as a variable selecting hard coatings such as TiN and TiC, and a low friction coating such as W-C:H. Experimental results showed that microstructural characteristics of the substrate as well as chemical and mechanical properties of the coating have an important influence in the overall coated system behavior. Concerning substrate influence, differences are clearly evidenced by considering coating detachment under contact fatigue as the critical damage mechanism, specifically for a TiN coating deposited by PVD. On the other hand, conventional scratch tests and even tests under monotonic spherical indentation, were not able to discriminate differences on the mechanical response of the three coated steels studied. In this regard, microstructural effects at the substrate level were rationalized on the basis of crack nucleation resistance of the existing primary carbides as the main reason for the distinct adhesive fatigue response observed. Hence, the optimum intrinsic strength/toughness of primary carbides in HWS and Universal steels as well as their finer and more regular morphology, as compared to the 1.2379 steel, were suggested as key factors for the improved contact fatigue strength exhibited by their corresponding coated systems. This was particularly true for the PM tool steel, where adhesive fatigue failure was completely suppressed as a consequence of their finer and homogeneously distributed primary carbides. Regarding coating properties, droplets were discerned to be detrimental seeds for crack nucleation and cohesive failure at the film surface. Delamination resistance of TiN deposited on a steel substrate Universal under cyclic contact loads increased significantly by using a process of low-pressure chemical vapour deposition.La incorporación de recubrimientos de alta dureza en el diseño de utillajes de conformado ha adquirido una importancia relevante en los últimos años. Dentro de la amplia gama de técnicas destinadas a la modificación superficial, la deposición de recubrimientos a partir de fase vapor suele ser la más idónea para cubrir con los exigentes requisitos de acabado superficial y tolerancias dimensionales que precisan ciertas herramientas, específicamente aquellas destinadas al sector automotriz. Sin embargo, aún cuando las capas finas reducen el impacto de las elevadas solicitaciones tribológicas, el fallo vinculado a fatiga por contacto sigue representando un problema a combatir en los utillajes de conformado. Este fenómeno se ha enfatizado en procesos convencionales de embutición, corte y troquelado por la introducción de chapas elaboradas de aceros de alta resistencia que requieren de impactos de mayor presión. Desde esta perspectiva, el sustrato juega un papel primordial como soporte de carga y cualquier daño subsuperficial que ocurra en él puede incidir en el desprendimiento prematuro de la capa, acelerando así el proceso de desgaste. Actualmente son escasas las técnicas estandarizadas diseñadas para evaluar el comportamiento de un sistema sustrato-recubrimiento sometido a solicitaciones de carga por contacto cíclico. Es por ello que el objetivo de este trabajo consistió en realizar un estudio sistemático de la respuesta a la fatiga por contacto esférico en sistemas integrados por capas finas cerámicas depositadas sobre aceros de herramienta para trabajo en frío. En este sentido, la simplicidad y reproducibilidad experimental a pequeña escala hacen del ensayo por indentación esférica una técnica fiable para inducir un elevado campo de tensiones con cargas puntuales relativamente bajas. Con ello fue posible comparar la respuesta al contacto esférico bajo solicitaciones monotónicas y cíclicas, donde el nivel de degradación de los sistemas por efecto de la fatiga se evaluó en términos de la aparición tanto de daño de carácter cohesivo como del fallo en la intercara sustrato-recubrimiento. La selección de materiales se realizó a partir de la premisa de sistemas recubiertos utilizados o potencialmente aplicables en el sector de los utillajes de conformado. El estudio se dividió en dos partes: una primera utilizando como variable el “sustrato” para determinar la influencia microestructural de tres calidades de aceros herramienta para trabajo en frío; y por la otra, empleando como variable el “recubrimiento”, utilizando para ello capas finas de alta dureza de TiN y TiC, así como un recubrimiento de bajo coeficiente de fricción de W-C:H. Los resultados demostraron que tanto las características microestructurales del sustrato como las propiedades químicas y mecánicas del recubrimiento son variables trascendentes en el comportamiento global del sistema. Por un lado, la influencia de la configuración microestructural del acero recubierto se hizo evidente al observar diferencias en la aparición del mecanismo de delaminación, específicamente para la capa de TiN depositada por PVD. Dichas diferencias no fueron distinguibles utilizando un ensayo convencional de rayado, ni simples indentaciones bajo solicitaciones de carga monotónica, pero si mediante la aplicación de cargas repetitivas por indentación esférica. Se identificó como parámetro relevante la combinación óptima entre la resistencia y la tenacidad intrínseca de los carburos primarios, específicamente de los aceros Universal y HWS, así como la morfología más redondeada, menor dimensión y distribución más homogénea de dichos carburos, comparados con los existentes en el acero 1.2379. En referencia al recubrimiento, se observó que la presencia de microgotas es un fenómeno crítico que favorece la nucleación de fisuras. La resistencia al desprendimiento del TiN bajo solicitaciones de contacto cíclico, aumentó significativamente al utilizar un proceso LPCVD.DOCTORAT EN CIÈNCIA DELS MATERIALS I ENGINYERIA METAL·LÚRGICA (Pla 1998)Universitat Politècnica de CatalunyaLlanes, L. M. (Luis Miguel)Universitat Politècnica de Catalunya. Departament de Ciència dels Materials i Enginyeria Metal·lúrgica201220122012info:eu-repo/semantics/doctoralThesisinfo:eu-repo/semantics/publishedVersion287 p.application/pdfapplication/pdfhttp://hdl.handle.net/10803/96672https://dx.doi.org/10.5821/dissertation-2117-94674TDX (Tesis Doctorals en Xarxa)reponame:TDR. Tesis Doctorales en Redinstname:CBUC, CESCAEspañolL'accés als continguts d'aquesta tesi queda condicionat a l'acceptació de les condicions d'ús establertes per la següent llicència Creative Commons: http://creativecommons.org/licenses/by-nc/3.0/es/http://creativecommons.org/licenses/by-nc/3.0/es/info:eu-repo/semantics/openAccessoai:www.tdx.cat:10803/966722026-06-14T12:46:07Z
score 15.301603

Similares en LA Referencia