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Ethanol has emerged as a promising alternative to fossil fuels, but its use can lead to significant dilution in lubricants, particularly during cold start or heavy traffic. This dilution can affect the performance of additives, including friction modifiers like molybdenum dithiocarbamate (MoDTC), which are designed to reduce friction under extreme contact conditions. Prior research suggests that ethanol may impact the performance of MoDTC, prompting this study’s goal to investigate the effects of ethanol on MoDTC tribofilms and their friction response under boundary lubrication conditions. Therefore, reciprocating tribological tests were performed with fully formulated lubricants containing MoDTC with varying ethanol concentrations. The results indicate that a critical ethanol dilution level inhibits friction reduction by MoDTC activation, resulting in friction coefficients (COFs) similar to the base oil. Surfaces tested with simple mixtures of polyalphaolefin (PAO) + MoDTC showed increased COFs with added ethanol. Analysis of tested surfaces using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy near the edge structure (XANES) revealed the presence of sulfates, MoO3, MoS2, and MoSxOycompounds in the tribofilms formed on the surfaces, with and without ethanol diluted in the lubricant. However, the addition of ethanol increased the sulfates and MoO3content of the tribofilms at the expense of friction-reducing compounds such as MoS2and MoSxOy. These findings suggest that ethanol dilution in lubricants containing MoDTC creates an oxygen-rich interfacial medium that favors the formation of compounds with insufficient friction-reducing capabilities.

When using powder particles in thermal plasma processes, partial evaporation of the particles may occur during the plasma–particle interaction. This research proposed the study of the parameters that cause evaporation with the aid of an experimental setup for the validation of an analytical model. To quantify evaporation, two experiments were carried out: the first one involved deposition of a coating on a substrate, and the second one without deposition. The model showed differences in evaporation when the interaction of the particles with the photons emitted by the plasma is considered. The particle radius size can influence the photon absorption efficiency and the electron emission current from the particle surface during the process. This can cause an increase in the final evaporation rate. In this research, evaporation was obtained as a function of the injected plasma mass considering the different particle size distributions. The experiments showed significant evaporation during thermal plasma processing of alumina powder, but evaporation reduced for higher feed rates.

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The use of synthetic fiber cables has substantially increased in the marine area due to their advantages and wide application, where they need to have excellent performance during their useful life. However, there are some mechanical effects that influence the degradation of the material, in particular wear. Among different types of wear in polymeric cables, small relative movements between the polymeric yarns may cause yarn-on-yarn wear. This study analyzes how the yarn-on-yarn wear between the monofilaments that compose the multifilament polymeric cable reduces the load that the filaments can support, impacting the number of cycles before rupture of the synthetic fiber. The procedure involved carrying out standardized yarn-on-yarn wear tests on two types of fibers (polyester and polyamide) under different tensile loads and environments (dry, water and saline). The worn regions were evaluated in a scanning electron microscope (SEM) to evaluate the acting wear mechanisms. It was noticed that the monofilaments tested in humid and saline environments showed longer life before rupture when compared to dry tests. This correlated well with the wear mechanisms found on the worn filaments via SEM, where tests in aqueous conditions showed much less severe wear mechanisms. Another interesting finding was that although the standard yarn-on-yarn test refers to abrasion resistance, the wear mechanisms found in the worn multifilaments seemed mostly related to adhesion and contact fatigue.

Surface textures with micro-scale feature dimensions still hold great potential to enhance the frictional performance of tribological systems. Apart from the ability of surface texturing to reduce friction, surface textures can also be used to intentionally increase friction in various applications that rely on friction for their adequate functioning. Therefore, this review aims at presenting the state-of-the-art regarding textured surfaces for high-friction purposes. After a brief general introduction, the recent trends and future paths in laser surface texturing are summarized. Then, the potential of surface textures to increase friction in different applications including adhesion, movement transmission and control, biomimetic applications, and road-tire contacts is critically discussed. Special emphasis in this section is laid on the involved mechanisms responsible for friction increase. Finally, current short-comings and future research directions are pointed out thus emphasizing the great potential of (laser-based) surface texturing methods for innovations in modern surface engineering.

Inconel®625 alloy is a corrosion-resistant nickel-based superalloy, often deposited onto cheaper substrates due to its high cost. In this research, deposition of Inconel®625 was carried out by MIG/MAG (metal inert gas/metal active gas) welding process due to its ease of operation, automation and productivity. The main purpose of this work is to evaluate the shielding gas and substrate thickness on the cooling rate, dilution and microstructure of Inconel®625 coatings welded by the MIG/MAG process. The cooling rate during deposition was measured using thermocouples. Dilution was evaluated from macrographs of cross section of the welded coatings using ImageJ software. The microstructure of the coatings was assessed via SEM/EDS (scanning electron microscope/energy dispersive spectroscopy) and X-ray diffraction (XRD). The results showed that cooling rates were higher for plates welded with Ar + 25% He, leading to lower dilution. In the microstructure, a γ-Ni matrix with precipitated phases of Mo and Nb was identified.

The tribological performance of many cylindrical components can be improved when an array of micro-cavities, often dimples, is produced on their surface, known as surface texturing. However, the production of textured surfaces on large areas at low cost and suitable texturing time remains a challenge, which is essential for industrial application and large-scale production. Maskless electrochemical texturing (MECT) draws attention as a very promising way to produce textured surfaces for journal bearings and cylinder liners of combustion engines. In this study, we propose a new configuration for the texturing chamber used in classical MECT. A new apparatus configuration is developed, where the electrolyte flows parallel to the textured region, in order to reduce the costs involved, improve the electrolyte flow and thus the efficiency of the process. Furthermore, the use of an adhesive patterned mask is investigated as a way to create the required insulation, eliminating the need for the tool perforation process. A voltage of 12 V, with texturing times of 1, 3 and 5 min, and an inter-electrode gap of 400 μm, enabled the production of dimples for a range of 650–1000 μm in diameter and 5–25 μm in depth in low carbon steel cylindrical surfaces with good reproducibility. Preferential dissolution of the ferrite was observed, probably due to its anodic nature in relation to the cementite.

The surfaces of dental implants are generally modified as an attempt to improve osseointegration. Three surface characteristics of implants are regarded as relevant in the process of bone formation: chemical composition, surface energy and topography. The topography of threaded implants is difficult to measure by conventional equipments with mechanical contact, so optical measuring equipments are preferred. However, implants with large thread angles may have the topography overestimated by the optical measuring equipment due to errors caused by scattering of the reflected light. This paper proposes a new methodology to measure implants with internal thread angle larger than 70° via laser interferometry, positioning the implant with an inclination angle in relation to the equipment base. The results were compared with results for flat discs, produced with the same surface treatment of the implant. Regarding surface energy of implants, most studies use measurements for flat discs, but it is questionable whether the results represent the implant itself. Here, two new methods were proposed to characterize the surface energy of real implants: a qualitative method related to the phenomenon of capillarity and a quantitative method with different liquids of known surface tension. It was found that the topography of the thread flanks is considerably different from the topography of the discs and it is believed that the geometry of the implant influences the surface treatment. The proposed quantitative methodology to analyze the surface energy allowed to detect differences between two commercial implants tested.

Robots have been increasingly used in applications involving welding of large metal structures, such as the naval industry, ensuring higher efficiency and repeatability at lower costs. However, inadequate communication between the robotics and the welding system can lead to internal and surface defects in the final product. Problems that occur during welding can be detected with the help of visual inspection. In the present work a passive monocular camera was used to quantify the texture found in weld beads as part of a fully-computerised vision system. The textures identified were associated with the presence of welding discontinuities. An algorithm based on Principal Component Analysis was developed to analyse weld beads, where part of the beads was produced using conditions that purposefully resulted in welding discontinuities, identifying the most important features that characterized one group with healthy beads and another group containing discontinuities. After this stage, a machine learning method was used in new weld beads, in order to classify them as healthy or defective. The accuracy of the proposed method for texture identification was 96.4%.

This paper aims to present and discuss simplified models to estimate the measurement uncertainty when determining circularity and cylindricity deviations using coordinate measuring machines (CMM). The work was carried out according to the following steps: (i) analysis of the known Standards and documents used for uncertainty determination; (ii) analysis of the measurement system (CMM), identifying the variables that influence the determination of geometry deviations; (iii) development of a mathematical model for the measurement process; (iv) development of a routine to evaluate uncertainty; (v) validation of the model through experimental tests, comparing the obtained results with those using models existing in the literature. It was concluded that the models presented are adequate and easy to be applied.