Influence of the stainless-steel microstructure on tribological behavior and surface integrity after ball burnishing

Burnishing is a plastic deformation process that reduces roughness while increasing hardness by introducing compressive residual stresses near the surface zone. These improvements will depend mainly on two fundamental variables: the applied load and the friction derived from the tool–surface interaction. Nevertheless, microstructural differences in the materials have not yet been considered within this interaction. This leads to a generalization of the process that can result in the failure of industrial components. Therefore, the aim of this work is to study the microstructural influence of the ball-burnishing process from a tribological perspective. Thus, martensitic and austenitic stainless steels were evaluated in terms of friction and surface integrity. The results show that parameterizing the process according to the tool–surface interaction is critical since improvements depend on friction as a function of the availability of plastic deformation of the crystallographic structures.Peer ReviewedObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraPostprint (published version

Experimental validation of ball burnishing numerical simulation on ball-end milled martensitic stainless-steel considering friction and the initial surface topography

Numerous simplified numerical models have been established to optimize the ball burnishing of steel surfaces. Nevertheless, their conceptualization has not considered the tool–part interaction, leading to an unsatisfactory process parameterization. As a solution, a structured numerical simulation has been defined that reproduces this interaction by several friction coefficient approximations. This study provides the tribological process inputs (friction and initial surface conditions) to this model, adapting it to a pre-textured martensitic precipitation hardening stainless-steel. Results show the versatility of the model to reproduce the surface integrity alterations. Hence, this consistent model configuration can be postulated as an economical and efficient approach to tackle ball burnishing parameterization according to the applicability of the manufactured steel parts.Peer ReviewedObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraPostprint (published version

Tool-part tribological interaction assessment for continuous deformation processes

Tesi amb menció de Doctorat Internacional i de Doctorat Industrial(English This dissertation is an experimental assessment of the tool-part tribological interaction of continuous deformation processes: ball burnishing as a superfinishing process and wire drawing as a bulk deformation process. Through the integration of friction as their fundamental parameter, these processes can be optimized. Thus, after the determination of the coefficient of friction, its impact on the final components surface integrity (hardness, roughness, and residual stresses), as well as the resulting wear mechanisms (adhesion and abrasion) from the sliding contact between hardmetal (WC/Co) and the treated materials (stainless-steel and aluminum alloy), has been analyzed by means of advanced characterization techniques such as: X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy dispersive x-ray analysis (EDX) and confocal scanning optical microscopy (CSOM). The results have shown that beyond the operational parameters and the macro-contact conditions, the influence of the micro-contact, microstructure and chemical composition, represent critical points in the tribological behavior of each process. In addition, these experimental outcomes constitute validation tools for numerical models, allowing integral configurations that surpass the simplified models that so far have not achieved adjustments in terms of surface finish and residual stresses, simultaneously. Therefore, potential solutions to the misalignments of each study case have been established from the analysis of a hitherto underestimated factor: friction.)(Español) Esta disertación trata sobre la evaluación experimental de la interacción tribológica herramienta - pieza para procesos de deformación continua: el bruñido con bola como proceso de superacabado y el trefilado de alambre como proceso de deformación masivo. Mediante la integración de la fricción como su parámetro fundamental, estos procesos pueden ser optimizados. Así, después de la determinación del coeficiente de fricción, su impacto en la integridad superficial de los componentes (dureza, rugosidad y tensiones residuales) y en los mecanismos de desgaste resultantes (adhesión y abrasión) del contacto por deslizamiento entre el metal duro (WC/Co) y los materiales tratados (acero inoxidable y aleación de aluminio), se ha analizado mediante técnicas de caracterización avanzadas: Difracción de rayos X (DRX), microscopía electrónica de barrido (FE-SEM), dispersión de energía de rayos X (EDX) y microscopía óptica confocal (CSOM). Los resultados muestran que más allá de los parámetros operativos y de las condiciones de macro-contacto, la influencia del micro-contacto, la microestructura y la composición química, representan puntos críticos en la tribología de cada proceso. Además, estos resultados constituyen herramientas de validación de modelos numéricos, permitiendo configuraciones integrales que superan los modelos simplificados que hasta ahora no han logrado ajustes en acabado superficial y tensiones residuales, simultáneamente. De esta manera, se han establecido soluciones a partir del análisis de un factor hasta ahora subestimado: la fricción.Postprint (published version

Tool-part tribological interaction assessment for continuous deformation processes

Tesi amb menció de Doctorat Internacional i de Doctorat Industrial(English This dissertation is an experimental assessment of the tool-part tribological interaction of continuous deformation processes: ball burnishing as a superfinishing process and wire drawing as a bulk deformation process. Through the integration of friction as their fundamental parameter, these processes can be optimized. Thus, after the determination of the coefficient of friction, its impact on the final components surface integrity (hardness, roughness, and residual stresses), as well as the resulting wear mechanisms (adhesion and abrasion) from the sliding contact between hardmetal (WC/Co) and the treated materials (stainless-steel and aluminum alloy), has been analyzed by means of advanced characterization techniques such as: X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy dispersive x-ray analysis (EDX) and confocal scanning optical microscopy (CSOM). The results have shown that beyond the operational parameters and the macro-contact conditions, the influence of the micro-contact, microstructure and chemical composition, represent critical points in the tribological behavior of each process. In addition, these experimental outcomes constitute validation tools for numerical models, allowing integral configurations that surpass the simplified models that so far have not achieved adjustments in terms of surface finish and residual stresses, simultaneously. Therefore, potential solutions to the misalignments of each study case have been established from the analysis of a hitherto underestimated factor: friction.)(Español) Esta disertación trata sobre la evaluación experimental de la interacción tribológica herramienta - pieza para procesos de deformación continua: el bruñido con bola como proceso de superacabado y el trefilado de alambre como proceso de deformación masivo. Mediante la integración de la fricción como su parámetro fundamental, estos procesos pueden ser optimizados. Así, después de la determinación del coeficiente de fricción, su impacto en la integridad superficial de los componentes (dureza, rugosidad y tensiones residuales) y en los mecanismos de desgaste resultantes (adhesión y abrasión) del contacto por deslizamiento entre el metal duro (WC/Co) y los materiales tratados (acero inoxidable y aleación de aluminio), se ha analizado mediante técnicas de caracterización avanzadas: Difracción de rayos X (DRX), microscopía electrónica de barrido (FE-SEM), dispersión de energía de rayos X (EDX) y microscopía óptica confocal (CSOM). Los resultados muestran que más allá de los parámetros operativos y de las condiciones de macro-contacto, la influencia del micro-contacto, la microestructura y la composición química, representan puntos críticos en la tribología de cada proceso. Además, estos resultados constituyen herramientas de validación de modelos numéricos, permitiendo configuraciones integrales que superan los modelos simplificados que hasta ahora no han logrado ajustes en acabado superficial y tensiones residuales, simultáneamente. De esta manera, se han establecido soluciones a partir del análisis de un factor hasta ahora subestimado: la fricción.DOCTORAT EN ENGINYERIA MECÀNICA, FLUIDS I AERONÀUTICA (Pla 2013