Abrasive wear is a wear mechanism that results in a loss of material from the interaction of a surface with hard particles. This type of wear is frequently found in the surface of machining tools. Microscale abrasion equipment is often used to characterize the resistance to abrasive wear of a surface. The different parameters able to control micro-abrasion wear tests, such as ball rotation, sliding distance between ball and surface sample, abrasive slurry concentration, normal load acting on the sample, and abrasive flow rate over the sample, have been widely studied. The combination of different variables, including sliding distance, concentration of abrasive particles, their hardness, and size of abrasive particles, promotes the transition between two-body, three-body, or mixed abrasive wear modes. However, the influence of the ball surface on the dragging of abrasive particles, which is reflected in the wear modes, is still poorly studied. One of the variables possible to control and less studied is the influence of the ball surface texture on the dragging of abrasive particles in microabrasion wear tests. This work intends to correlate the effect of different testing times (500, 1000, and 1500 cycles) and different concentrations of 3 m Al2O3 abrasive slurry (25, 35, and 45 g/100 mL) on the micro abrasion resistance of a TiN thin coating film, using balls of AISI 52100 steel whose texture and roughness were prepared by 60 s chemical etching. The rotation speed of each test was 80 rpm, applying a normal load of 2 N. Subsequently, the craters were carefully analyzed using SEM to evaluate the transition of the wear mode as a function of the applied load, the abrasive particle concentration, and the sliding distance. The textured ball tracks were observed via SEM to assess the particle dynamics. The results showed that, contrarily to what is reported in the literature regarding wear modes where rolling is promoted with increasing abrasive concentration, in this work grooving took place instead. This is a result of the rough balls use in the experiments which, due to the embedment of abrasive particles in the ball grooves, promotes the abrasion mechanism. The higher the abrasive concentration, the higher the grooving mechanism, since more particles are available to scratch the surface.

Silver-added titanium nitride (Ag:TiN) thin films were deposited by DC reactive sputtering with Ag contents ranging from 0 to ∼50 at.% on silicon and glass substrates, aiming at studying their potential application as bio-electrodes. The coatings were characterised regarding their composition, morphology and structure, and their influence on the variation of the electrical resistivity and thermal properties. The sputtered films’ behaviour was consistently divided into three main zones, defined mainly by the amount of Ag incorporated and the corresponding changes in the structural and morphological features, which affected both the electrical and thermal response of the films. With increasing Ag concentration, the coatings evolve from a nitride/compound-like behaviour to a metallic-like one. Resistivity values suffer a strong decrease due to the increase of compactness of the coatings and the formation of highly conductive Ag phases, counterbalancing the grain size decrease effects promoted by the hindered growth of the crystalline TiN phases. In good agreement with the electrical resistivity evolution, a similar trend was found in the effusivity values, reflecting a significant degradation of the heat conduction mechanisms in the films as the silver content was increased.

During the last decades, studies involving the bainitic structure have attracted researchers for combining high strength and high ductility. Bainitic steel be potentially useful in structures suffering rolling and/or sliding fatigue, e.g. rails railway, mining components, bearings and shafts. These properties have been obtained by carefully designing the alloy and an adequate austempering heat treatment. However, the material with these properties does not facilitate machinability in manufacturing processes, making it necessary to work the material in an annealed state. Therefore, this work aims to contribute to the tribological analysis of the contact between molten steel in the annealed state against carbide and cermet (coated with Titanium Nitride (TiN)), which are materials widely found in cutting tools. For this purpose, pin-on-disk (PSD) tests were carried out in order to analyze the evolution of the friction coefficient (µ), specific wear coefficient (k) and the behavior of induced deformations. The results indicated that the lowest µ values were observed using posts with cermet substrate, which suggests that it was influenced by the chemical composition of this substrate. Regarding the k and deformed layer thickness for both substrates, there was no significant variation in the values found. Smooth surfaces were observed for the tracks worn in all evaluated conditions and signs of plastic deformation (ploughing) which suggests the action of smooth abrasion mechanisms. However, it was observed that both the adhesion and the abrasion mechanism influenced the µ for the cermet substrate in the replica condition. The work contributes to evaluate the influence of different substrates and identify the wear mechanisms present.  

RESUMEN La aplicación de recubrimientos cerámicos del tipo nitruros, carburos o diamante, sobre sustratos de acero aporta diversas bondades tribológicas. Sin embargo elevados gradientes de dureza y problemas de adhesión con el sustrato pueden perjudicar el desempeño de estos recubrimientos frente a la Fatiga de Contacto por Rodadura (FCR). Numerosos estudios realizados sobre aceros que mantienen la dureza a elevadas temperaturas, recubiertos con films cerámicos, se han enfocado en esta cuestión. En el presente trabajo se estudia el uso de un acero de bajo costo, como el SAE 1050, con un tratamiento superficial combinado, consistente en un recubrimiento de TiN por Deposición Física de Vapor (PVD), y un temple superficial posterior por inducción que proporcione al sustrato la resistencia sub-superficial necesaria para soportar las tensiones del macrocontacto. La secuencia de tratamientos propuesta, a diferencia de la usualmente empleada (temple+PVD), pretende mantener la dureza de temple del sustrato, aunque resulten inciertas las consecuencias sobre el recubrimiento. Los ensayos para evaluar la resistencia a la FCR se realizaron con una máquina tipo arandela plana, en la cual una probeta en forma de disco gira sobre un conjunto de bolillas correspondientes a un rodamiento de empuje axial, bajo la acción de una carga normal. Los resultados fueron analizados de manera estadística y el daño resultante fue observado con microscopio óptico y microscopio electrónico de barrido (SEM), en complemento con mapeos de espectrometría de dispersión de energía de rayos X (EDS). En el caso estudiado, el tratamiento realizado permitió obtener algunas de las ventajas típicas de los recubrimientos, sobre todo aquellas relacionadas con la fricción y el desgaste adhesivo y abrasivo, sin una drástica modificación en la vida a la FCR, en sustratos de aceros de construcción. También se realizaron ensayos de Difracción de rayos X (DRX) para evaluar la modificación del recubrimiento como consecuencia del temple superficial.

The synthesis of nanosized Ti-based nanogranules via plasma spraying is reported. The synthesis route involved use of both nitrogen and oxygen gases with varying results. In the case of nitrogen, a mixture of titanium nitrides were produced, yielding both the Ti2N and the sub-stoichiometric TiN0.61 compounds. In the case of oxygen, both the stoichiometric rutile and TiO ceramic phases were indexed. Based on EDS analysis, even fractional oxygen concentrations caused tungsten impurities which originated from the cathode electrode. The method yielded particle mass median sizes of the order of 15nm and the smallest particles detected were 5nm.

In this paper we studied the influence of pre-treating the surface of 100Cr6 steel by ion beam nitriding at low temperature (380°C) on the surface topography and wear resistance of thin TiN coatings deposited by reactive ion beam assisted deposition. The specimens were characterized by grazing incidence X-ray diffraction, scanning electron microscopy and atomic force microscopy. The wear resistance of the TiN-coated specimens was evaluated by means of ball on disc tests. The results showed that application of a preliminary ion beam nitriding treatment slightly increased the surface roughness but improved the wear resistance of the 100Cr6 steel due to the formation of a diffusion zone containing the γ'-Fe4N nitride combined with the TiN coating.

Titanium nitride (TiN) coatings are widely used in machining because of its mechanical characteristics which modify the surface of the substrate increasing the capacity of load support and reduction of friction, while a coating as diamond-like carbon (DLC), which also has interesting mechanical properties, needs better attention. In this sense, the development of new coatings such as DLC is as important as wear analysis techniques. This work discusses the methods available to assess abrasive wear of coatings. For this, it has been used the data of the crater volume formed in ball cratering test and compared the difference between the specific wear coefficients of substrate and coating (ks and kc). These coefficients depend of the methods used for data analyses, thus, it has been used four equations to calculate ks and kc. Moreover, profilometry (pf) has been used to calculate the volumes, and thus ks and kc. Also, the roughness of the coatings, the thickness, the images corresponding to the crater formed, the coefficient of friction, the data obtained in wear tests due to the volume removed and, in the end, a comparison between ks and kc by different methods of data analyzes are presented.