The use of plant-based lubricants is a sustainable alternative to petrochemical lubricants. Their main advantages include proven tribological performance, higher biodegradability in the environment, and the absence of health hazards when inhaled, ingested, or in contact with the skin. In this study, nine best-selling commercial lubricants were purchased and compared with two proposed sustainable alternatives derived from plant-based resources. The alternative wet lubricant that was developed demonstrated superior tribological performance compared to the selected commercial lubricants. Meanwhile, the alternative dry lubricant exhibited a greater load capacity and high wear resistance in the presence of micrometric Al₂O₃ particles at 20 N. The results indicated that a proper formulation of plant-based resources in lubricants can achieve the same or even better functional performance than conventional lubricants, which are currently classified as hazardous under European regulations.

This study investigates the feasibility of utilizing low-cost Fused Deposition Modeling (FDM) technology to produce durable Tactile Graphics (TG) for outdoor environments. Five common FDM thermoplastics—PLA, ABS, ASA, PET-G, and PP—were evaluated for printability, geometric quality, wear resistance, UV resistance, and chemical resistance. Results indicate that PLA offers high geometric precision and ease of printing, rendering it suitable for low-cost indoor applications. For outdoor environments, PET-G exhibited the best overall performance in wear and chemical resistance, while ASA demonstrated significant UV degradation. PP, although durable, presented challenges in printability. ABS and ASA exhibited a favorable trade-off between printing quality and environmental resistance. A multi-objective selection function was developed to guide material selection based on specific TG requirements. For indoor applications prioritizing quality and cost-effectiveness, PLA is recommended. For outdoor TGs requiring durability and chemical resistance, PET-G is preferred. ABS offers a balanced option with moderate durability and good geometric quality. This study provides a comprehensive framework for expanding FDM applications in accessible TG manufacturing for various environments and use cases.

El objetivo de este trabajo consiste en el desarrollo de recubrimientos cerámicos autolubricantes a base de Al2O3-3%TiO2 con la adición del 3% de nanoplaquetas de grafeno (GNPs). Se ha estudiado la influencia de los GNPs sobre las propiedades mecánicas y el desgaste en un medio abrasivo. Estos recubrimientos se han depositado sobre un sustrato de acero inoxidable AISI 304 mediante la técnica de proyección térmica por llama (OF). La microestructura de los recubrimientos se ha evaluado utilizando microscopía electrónica de barrido FE-SEM y análisis por Energías Dispersivas de Rayos X (EDX). Además, se ha empleado espectroscopia Raman para identificar la presencia de grafeno en la microestructura del recubrimiento cerámico. La porosidad de los recubrimientos se ha cuantificado mediante un software de análisis de imagen J-Image. La microdureza se ha determinado utilizando un microdurómetro Vickers con una carga de 200 g durante 15 s. Los ensayos de desgaste en medios abrasivos se han realizado en un banco tribológico mediante el sistema pin-on-disc en condiciones de laboratorio, aplicando una carga constante de 20 N y una velocidad de deslizamiento variable entre 0.08 y 0.005 m/s, incrementando la velocidad cada 40 m de recorrido hasta alcanzar una distancia total de 120 m. Como medio abrasivo, se ha empleado papel de SiC con una granulometría de 320. La incorporación de GNPs en los recubrimientos cerámicos comerciales influye significativamente en las propiedades mecánicas y en la resistencia al desgaste abrasivo. Los resultados demuestran que la adición del 3% de GNPs en recubrimientos nanoestructurados de Al2O3-3%TiO2 reduce la porosidad hasta un 6,6% y aumenta la dureza hasta un 11%. La incorporación de GNPs en los recubrimientos nanoestructurados de Al2O3-3%TiO2 es capaz de reducir el coeficiente de rozamiento y la tasa de desgaste en medios abrasivos hasta en un 13,5 y 67% respectivamente con respecto al recubrimiento cerámico sin adiciones de GNPs, prolongando así la vida útil del recubrimiento modificado. Este desarrollo puede ser un factor clave en la selección y el diseño de uniones cinemáticas que operen en condiciones severas.

NiCrBSi coatings are widely used for high-temperature surface protection, although their oxidation resistance can be limited by oxygen ingress through splat boundaries, pores, and other defects inherent to thermally sprayed microstructures. This study investigates the effect of Al2O3 reinforcement on the oxidation behavior of oxy-fuel sprayed NiCrBSi coatings exposed to synthetic air at 850 °C for 50 h. Unreinforced NiCrBSi and NiCrBSi reinforced with 40 wt.% Al2O3 were deposited on AISI 304 stainless steel and characterized before and after oxidation. Microstructural evolution, oxide formation, and phase stability were examined using SEM/EDS, elemental mapping, and X-ray diffraction, while oxidation kinetics and mechanical performance were evaluated by thermogravimetric analysis and cross-sectional microhardness measurements. The unreinforced coating exhibited extensive internal oxidation along interlamellar regions, formation of a continuous oxide network, and degradation of the lamellar microstructure, resulting in greater mass gain and hardness reduction. In contrast, the Al2O3-reinforced coating showed significantly lower internal oxidation, improved γ-Ni phase retention, and enhanced microstructural stability due to the presence of thermally stable α-Al2O3 particles. Both coatings exhibited diffusion-controlled oxidation; however, the superior oxidation resistance of the reinforced coating resulted from microstructural control of oxygen transport rather than a change in oxidation mechanism. Al2O3 disrupted the connectivity of interlamellar diffusion pathways and increased oxygen-transport tortuosity, thereby restricting oxygen penetration, suppressing oxide growth, enhancing phase stability, and preserving mechanical integrity. These findings demonstrate that Al2O3 reinforcement effectively improves the long-term oxidation resistance of thermally sprayed NiCrBSi coatings by limiting internal oxidation through microstructural control of oxygen transport.