Desarrollo de un proceso de inducción de autolubricación mediante el uso de pastas de grafito para aceros producidos por press and sinter.
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Date
2025
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Universidad de Concepción
Abstract
En el presente trabajo se estudia el efecto en las propiedades mecánicas y tribológicas de un sistema auto lubricante ferroso producido por metalurgia de polvos cuyo proceso de impregnación de la fase lubricante, el cual para el presente estudio fue grafito, se realiza comprimiendo el cuerpo verde y previo a la etapa de sinterizado.
La hipótesis es que el grafito en los poros causará una cementación in situ durante la sinterización que reducirá la tasa de desgaste y el coeficiente de roce en seco del material. El objetivo es estudiar el efecto que esto tiene en el coeficiente de fricción y su evolución en el tiempo en contraste a muestras de referencia.
Se produjeron 3 tipos de muestras, rutas 1, 2 y 3. Ruta 1 representa el estudio principal, mientras que ruta 2 equivale al estándar industrial y ruta 3 es una variante. Las muestras de la ruta 1 fueron compactadas a 200 MPa, impregnadas por filtración de la pasta de grafito en poros aplicando 600 MPa sobre la pasta contra el cuerpo verde, y posteriormente sinterizadas a 1100°C. Las demás muestras fueron compactadas a 600 MPa para ruta 2 y a 200 MPa para ruta 3, sinterizadas a 1100°C y finalmente impregnadas a 600 MPa.
La microestructura se caracterizó mediante microscopía óptica y microscopía electrónica de barrido. Se determinó la micro dureza Vickers antes y se realizó la caracterización tribológica en un tribómetro universal utilizando una configuración de deslizamiento en seco con una geometría ball on flat reciprocante.
La cementación de la muestra de la ruta principal produce granos de perlita hasta los 1030 micrones de profundidad y muestra una porosidad inferior a la muestra compactada a 200 MPa antes de la impregnación, y superior a la compactada a 600 MPa antes de la impregnación.
Las muestras de la ruta 1 mostraron mayor dureza, coeficiente de fricción estable y por debajo de 0.25. Las muestras de la ruta 2 tuvieron la menor dureza y las muestras de la ruta 3 registraron una levemente superior a la anterior. Las 2 muestras de referencia parten con menor coeficiente de fricción, y las muestras de la ruta 2 eventualmente superan a las de la ruta 1. La muestra compactada a 600 MPa termina su régimen de lubricación antes, a pesar de ser la que alcanza menor coeficiente de fricción.
Se concluye que la impregnación por slurry es tecnológicamente viable, y que la primera etapa del ensayo está gobernada por las propiedades mecánicas de la superficie de las muestras.
In the present work, the effect on the mechanical and tribological properties of a self-lubricating ferrous system produced by powder metallurgy is studied. The process of impregnation of the lubricant phase which in the present study was graphite was carried out by compressing the green compact prior to the sintering stage. The hypothesis is that the graphite within the pores will cause an in situ cementation during sintering, which will reduce the wear rate and the dry friction coefficient of the material. The objective is to study the effect of this process on the coefficient of friction and its evolution over time in contrast to reference samples. Three types of samples were produced: routes 1, 2, and 3. Route 1 represents the main study, while route 2 corresponds to the industrial standard and route 3 is a variant. The samples from route 1 were compacted at 200 MPa, impregnated by filtration of the graphite paste into the pores by applying 600 MPa on the paste against the green compact, and subsequently sintered at 1100°C. The remaining samples were compacted at 600 MPa for route 2 and at 200 MPa for route 3, sintered at 1100°C, and finally impregnated at 600 MPa. The microstructure was characterized by optical microscopy and scanning electron microscopy (SEM). Vickers microhardness was determined prior to tribological testing, which was carried out in a universal tribometer using a dry sliding configuration with a reciprocating ball-on-flat geometry. The cementation of the main route sample produced pearlite grains up to 1030 microns deep and exhibited a porosity lower than that of the sample compacted at 200 MPa before impregnation, but higher than that of the one compacted at 600 MPa before impregnation. The route 1 samples showed higher hardness, a stable friction coefficient, and values below 0.25. Route 2 samples exhibited the lowest hardness, while route 3 samples registered slightly higher values. Both reference samples initially presented lower friction coefficients, and route 2 samples eventually surpassed those of route 1. The sample compacted at 600 MPa reached the end of its lubrication regime earlier, despite achieving the lowest friction coefficient. It is concluded that slurry impregnation is technologically feasible, and that the initial stage of the test is governed by the mechanical properties of the sample surfaces.
In the present work, the effect on the mechanical and tribological properties of a self-lubricating ferrous system produced by powder metallurgy is studied. The process of impregnation of the lubricant phase which in the present study was graphite was carried out by compressing the green compact prior to the sintering stage. The hypothesis is that the graphite within the pores will cause an in situ cementation during sintering, which will reduce the wear rate and the dry friction coefficient of the material. The objective is to study the effect of this process on the coefficient of friction and its evolution over time in contrast to reference samples. Three types of samples were produced: routes 1, 2, and 3. Route 1 represents the main study, while route 2 corresponds to the industrial standard and route 3 is a variant. The samples from route 1 were compacted at 200 MPa, impregnated by filtration of the graphite paste into the pores by applying 600 MPa on the paste against the green compact, and subsequently sintered at 1100°C. The remaining samples were compacted at 600 MPa for route 2 and at 200 MPa for route 3, sintered at 1100°C, and finally impregnated at 600 MPa. The microstructure was characterized by optical microscopy and scanning electron microscopy (SEM). Vickers microhardness was determined prior to tribological testing, which was carried out in a universal tribometer using a dry sliding configuration with a reciprocating ball-on-flat geometry. The cementation of the main route sample produced pearlite grains up to 1030 microns deep and exhibited a porosity lower than that of the sample compacted at 200 MPa before impregnation, but higher than that of the one compacted at 600 MPa before impregnation. The route 1 samples showed higher hardness, a stable friction coefficient, and values below 0.25. Route 2 samples exhibited the lowest hardness, while route 3 samples registered slightly higher values. Both reference samples initially presented lower friction coefficients, and route 2 samples eventually surpassed those of route 1. The sample compacted at 600 MPa reached the end of its lubrication regime earlier, despite achieving the lowest friction coefficient. It is concluded that slurry impregnation is technologically feasible, and that the initial stage of the test is governed by the mechanical properties of the sample surfaces.
Description
Tesis presentada para optar al título de Ingeniero/a Civil de Materiales.
Keywords
Lubricantes, Metalurgia de polvos, Grafito, Coeficiente de rozamiento