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Powder injection moulding and sintering were used to obtain iron-based self-lubricating composites in which SiC particles were used as precursors to generate graphite nodules dispersed in the composite matrix. Using thermodynamic simulations with DICTRA®, it was possible to predict the SiC dissociation in the ferrous matrix studied (Fe+0.6C). The evolution of the dissociation of SiC particles during...
The literature is controversial in relation to the influence of wear debris on tribological behaviour. Some works have shown that the presence of debris is fundamental to the formation of a protective tribolayer, thus reducing friction, whereas others showed that the presence of wear debris could contribute to increase friction coefficient due to the energy spent dragging them into the contact. This...
The synergistic effect between abrasion and corrosion has been widely investigated and debated, where according to some works this synergy accentuates wear, and for others attenuates it. Despite the considerable effort to understand the synergy between abrasion and corrosion, little progress has been made to understand this phenomenon for ferritic stainless steels. This paper analyses the micro abrasion-corrosion...
Cobalt alloys are used in several industrial applications due to their good mechanical properties at high temperatures. During manufacturing of 13% Cr super martensitic stainless steel seamless tubes by Mannesmann process, the hot rolling guides made of cast Co30Cr19Fe alloy are currently used, but present severe wear, limiting their service life. Seeking an alternative, three cobalt-based coatings...
PVD coatings have been used to improve the wear resistance of various tribological systems. In general, analytical models that describe the abrasive wear behaviour of ceramic materials do not take into account the presence of superficial flaws in ceramic coatings. Flaws are pores or protuberances present in the coating surface formed during the coating process. In this work, the percentage of superficial...
Aiming at the study of synergy between the abrasion and corrosion a new instrument, enabling the measurement of forces acting on the contact, has been designed. The test rig consists of a fixed-ball micro-abrasion tester, where the specimen is supported by a three-axis load cell, and an electrochemical cell. A very flexible protective membrane has been designed to isolate the load cell, located outside...
In the present investigation, the effect of the nature of the iron nitrides (γ′-Fe4N or ε-Fe2-3N) on the sliding wear of plasma nitrided unalloyed sintered iron is studied. Plasma nitriding was performed in an industrial scale plasma reactor using two different sets of operative parameters to produce microstructures composed of different dominant iron nitride phases, i.e., γ′-Fe4N and ε-Fe2–3N. Microstructural...
Polyether ether ketone (PEEK) composites and AISI 52100 steel are high-performance materials that are often selected for high stress tribological applications under solid and hydrodynamic lubrication. In this study, the viability of these materials as a pair for boundary-lubricated systems was evaluated. Tribo-tests to evaluate different characteristics were conducted: (i) the effect of metallic surface...
A new processing route to promote the in situ generation of solid lubricant particles has been presented recently. This route takes an advantage of a powder injection moulding process combined with a plasma-assisted debinding and sintering process (PADS). Graphite nodules were generated in situ in the volume of sintered steels during sintering simply by the dissociation of silicon carbide (SiC) particles,...
Triboscopy was proposed over 20 years ago, but despite the powerful insight it brings to analyse friction and wear with temporal evolution of localised events, its use is still limited. In this paper, triboscopy has been further developed. A LVDT sensor measures the position of the counter-body inside the wear track in a reciprocating tribometer. A high frequency acquisition system allows 10 points...
Using techniques such as scanning electron microscopy (SEM), micro-Raman spectroscopy and glow discharge optical emission spectroscopy (GDOES), this work aimed to develop a physico-chemical methodology for characterising tribolayers. Reciprocating sliding tests (DLC slides without rolling on a flat surface of AISI 304 stainless) under a special atmosphere (refrigerant R134a) were performed. The use...
The present work analyzed the wear behavior of surface modifications often used in cold rolling mill rolls. Different surface modifications were carried out on samples produced from a fragment of a rolling mill roll: i) shot blasting texturing using steel spheres (T); ii) chromium plating (C); iii) shot blasting texturing with subsequent hard chrome plating (TC); iv) and hard chrome plating with subsequent...
In this work, brass-infiltrated tungsten composites, applied in rock-drilling core sample collection, were sintered with different tungsten-matrix particle sizes and chemical compositions. The microstructure in each condition was characterized by scanning electron microscopy and the mechanical properties of each phase were analyzed by instrumented indentation testing. The tribological behavior of...
Polymers and polymer composites are commonly used as solid lubricants. Polyether–ether–ketone (PEEK) is an engineering thermoplastic with a very good combination of thermal and mechanical properties. Although PEEK presents relatively high friction coefficients during unlubricated sliding, the wear rates are remarkably low. Despite this potential as a good tribological material, the high performance...
During abrasive wear, the prevailing wear mechanism has been shown to be connected to the movement of the active particles present at the wear interface. Two particle dynamics can occur: (i) rolling, which is evidenced by the presence of indentations on the worn surface, and (ii) sliding, which produces scratching and/or ploughing. The particle dynamics can vary with the imposed tribological conditions...
Abrasive wear is currently classified according to different particle dynamics: (a) the sliding of active particles on the sample surface and (b) the rolling of abrasive particles between the surfaces. In this paper, instrumented laboratory tests are used to present a new methodology for the simulation of abrasive wear. The rolling of the abrasives is represented by a sequence of indentations, and...
Friction and wear control can be achieved primarily by considering the nature of the counter faces, together with the environmental conditions. In most cases, a transfer film is found on the sliding surfaces. The environment plays a crucial role on the kinetics of formation and on the composition of the transfer film, and thus strongly influences friction level and wears rates. In this paper, the...
High-chromium white cast irons are commonly used in applications requiring excellent abrasion resistance, as in the mining and mineral ore processing industry. Their excellent abrasion resistance is mainly due to their solidification microstructures. During their solidification, high levels of chromium (16–32%) lead to the formation of a high-volume fraction of eutectic M 7 C 3 -carbides,...
Recently, the micro-scale abrasive wear test has gained large acceptance in universities and research centers, being widely used in studies on the abrasive wear of materials. The purpose of this work is to relate a quantity called test severity (S test ) with the abrasive wear mode transition. The analysis took into consideration the hardness of the materials; the contact pressure (P) between...
During the hot rolling process the surface temperature of the rolling-mill rolls can reach values as high as 600°C. In these conditions, oxides, which have been usually considered as friction and wear reducing agents by acting as a solid lubricant, may grow on the surface and change the tribological behaviour of the roll–strip pair. In this work, the effect of temperature, normal load and pre-oxidation...
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