Mechanical Tribological Properties Research Articles

Influence of Plasma Arc Current and Gas Flow on the Structural and Tribological Properties of TiN Coatings Obtained by Plasma Spraying

This study investigates the development of TiN-based coatings using plasma spraying technology, focusing on how plasma arc current and working gas flow rate affect the coatings’ structural-phase composition and mechanical–tribological properties. The research highlights the potential and effectiveness of plasma spraying for TiN coatings. Results from scanning electron microscopy and nanoindentation tests show that the TiN coatings have a dense microstructure with strong adhesion. Tribological testing demonstrated that coatings deposited at a 250 A arc current displayed the lowest coefficient of dry friction and the lowest porosity (2.13%) compared to those deposited at 350 A and 450 A arc currents, which exhibited higher porosity (up to 10.45%).

High-temperature tribological performance of Y2O3-Doped Cu-Zn self-lubricating composite by SPS

The rare earth oxide Y2O3 exhibits excellent wear resistance and stability in engineering applications. Copper-zinc-based wear-resistant composites with varying Y2O3 contents were prepared using spark plasma sintering. Their mechanical tribological properties were studied over a wide temperature range from room temperature to 300 °C. The results indicated that the composites have good densification, and uniformly distributed matrix components. Adding an appropriate amount of Y2O3 can significantly refine the grain and improve the matrix's mechanical and tribological properties. In the above temperature range, the friction coefficient and wear rate appear the lowest values when the concentration is 1 %, and the wear mechanism changes from abrasive wear to adhesive wear with the increase of temperature.

Efecto del reprensado en las propiedades mecánicas de guías de válvulas fabricadas por pulvimetalurgia

Se determinaron la dureza, pérdida de masa y coeficiente de fricción, de guías de válvulas para motores de combustión interna fabricadas en latón por proceso de pulvimetalurgia, con el objetivo de conocer si cumplen con las exigencias que requiere un motor de combustión interna, utilizando como parámetro comparativo guías de válvulas comerciales de latón producidas por fundición. Se estudió, si las propiedades son homogéneas a lo largo de toda la guía de la válvula y se evaluó el proceso de reprensado que se lleva a cabo de manera adicional en la línea de producción. Se determinaron las durezas Brinell y Vickers; el coeficiente de fricción y la tasa de desgaste (ensayo pin on disk). Mediante microscopía electrónica de barrido y análisis metalográfico, se estudió el mecanismo de desgaste. Se llevó a cabo la determinación de la composición química de las guías y el efecto del reprensado cuantificando la porosidad superficial, mediante el software Analizador de imágenes Pro Plus®. Se puso de manifiesto que las piezas fabricadas por proceso de pulvimetalurgia presentaron valores inferiores en sus propiedades mecánico-tribológicas en comparación con las guías de válvula comerciales. Estos resultados permitirán mejorar las condiciones de fabricación de las guías mediante pulvimetalurgia.

Effect of the addition of Si into Nb2O5 coatings on their structural, optical, and mechanical properties

There are many polymorphs of Nb2O5, each with interesting properties that have been explored for biomedical, photocatalytic, and optical applications. However, Nb2O5 is not generally used for mechanical applications owing to its low hardness (8 GPa). The objective of this work was to evaluate the effects resulting from the addition of silicon (Si) into the Nb2O5 structure, with the aim of increasing its hardness through the formation of a nanostructured composite coating. In this paper, the authors report the structure and mechanical properties of Nb2O5 as a function of the silicon content (0–5.5 at. %). The coatings were deposited on silicon and D2 steel substrates using a confocal-dual magnetron sputtering system using a mixture of argon and oxygen (80:20) with each magnetron (Nb and Si targets) independently driven. The coatings were annealed at 550 °C to obtain a crystalline structure. However, analysis of the optical properties indicated the persistence of a substoichiometric amorphous phase. Despite the contribution of the amorphous phase, the mechanical–tribological properties were slightly improved after Si incorporation. The hardness reached a maximum of 17.6 GPa for the samples deposited at 50 W in the Si target, coupled with a reduction in both the coefficients of friction and wear.