In the context of developing an innovative seismic dissipation system, which aims to compromise on the steadiness of friction and processes costs, this work deals with the tribological characterization of an S355JR structural steel, whose surface has been preliminarily treated by different mechanical and galvanic processes. Tribological tests were performed in a pin-on-disk configuration and in reciprocating motion, using values of 1 Hz and 2 Hz as the motion inversion frequency, a constant normal load of 50 N, and variable test duration, according to the most frequent seismic events. The tribological system was composed of S355JR structural steel pins and disks of the same steel, which were alternatively treated by electrolytic nickel plating, electrolytic zinc plating, and two different shot peening processes. The results highlight that while electrolytic nickel increments the overall steadiness of the coefficient of friction (COF), electrolytic zinc plating guarantees the longest first steady-state stage and a COF lower than the one guaranteed by the coupling of untreated pins and disk.

In recent years, Golden Hard Anodizing (G.H.A.^®) has been developed as a variant of the traditional hard anodizing process with the addition of Ag⁺ ions in the nanoporous structure. The tribological properties of this innovative surface treatment are still not well understood. In this study, ball-on-disk tests were conducted in dry sliding conditions using 100Cr6 (AISI 52100) bearing steel balls as a counterbody and GHA^®-anodized EN AW-6082 aluminum alloy disks. The novelty of this work lies in the mapping of the wear properties of the tribocouple under different test conditions for a better comparison of the results. Three different normal loads (equal to 5, 10, and 15 N) and three different reciprocating frequencies (equal to 2, 3, and 4 Hz) were selected to investigate a spectrum of operating conditions for polished and unpolished G.H.A.^®-anodized EN AW-6082 aluminum alloy. Quantitative wear maps were built based on the resulting wear rate values to define the critical operating limits of the considered tribocouple. The results suggest that the coefficient of friction (COF) was independent of test conditions, while different wear maps were found for polished and non-polished surfaces. Polishing before anodizing permitted the acquisition of lower wear for the anodized disks and the steel balls.

High phosphorus Ni-P coatings, both unreinforced and modified by the addition of alumina (Al₂O₃) and zirconia (ZrO₂) nanoparticles, were manufactured by electroless deposition technique and heat-treated with different temperature and duration schedules. The effect of dehydrogenation (200 °C for 2 h) and its combination with crystallization heat treatment was studied in terms of microstructural changes and wear resistance. The amorphous structure of the coatings was not altered by the introduction of both Al₂O₃ and ZrO₂ nanoparticles, and the addition of 1.5 g/L of ZrO₂ yielded the highest microhardness due to better particles dispersion. Dehydrogenation improved hardness because of the early stages of grain growth; however, the greatest improvement in hardness (+120% compared to unreinforced Ni-P) was obtained after annealing at 400 °C for 1 h, because of the microprecipitation of the Ni₃P crystalline phase induced by thermal treatment. No detectable differences in hardness and microstructure were detected when annealing at 400 °C for 1 h with or without prior dehydrogenation; however, the dehydrogenated coatings exhibited a lower Young’s modulus. ZrO₂-reinforced coatings demonstrated improved wear resistance, and wear tests revealed that dehydrogenation is fundamental for lowering the coefficient of friction (−14%) and wear rate (−97%) when performed before annealing at 400 °C for 1 h. The analysis of the wear tracks showed that the non-dehydrogenated samples failed by complete coating delamination from the substrate, with abrasion identified as the predominant wear mechanism. Conversely, the dehydrogenated samples demonstrated better resistance due to the formation of a protective oxide layer, leading to an overall increase in the coating wear resistance.

This work investigates the tribological behavior of a machined S355JR structural steel in dry sliding conditions for the development of an innovative seismic dissipation system. Flat-ended pins and disks were made of the same structural steel to simulate the conformal contact of different device parts. Pins were machined by turning, while disks were milled and turned to obtain a nominal average surface Ra roughness ranging from 0.8 µm to 6.3 µm. The influence of the surface roughness on the coefficient of friction (COF), specific wear rate (SWR), and time to steady-state (TSS) was investigated. Tribological tests were conducted reciprocating motion in dry sliding conditions to simulate the operating conditions of the device, with 1 Hz and 2 Hz reciprocating frequencies and an applied normal load of 50 N. The Rsk and Rku roughness parameters helped to better understand the tribological response of milled and turned disks, having an influence on the TSS and SWR.

The present study examines the tribological behavior of an EN AW-4006 aluminum alloy subjected to two innovative hard anodizing processes involving the sealing of anodic oxide pores with Ag⁺ ions and tested in lubricated conditions. Four plant-based lubricants with different concentrations of fatty acids were considered. Wear tests were conducted using a ball-on-disk tribometer, employing a constant frequency oscillatory motion at 2 Hz and a maximum linear speed of 0.1 m/s. The investigation explores the influence of applied loads (5 N, 10 N, and 15 N) on the resulting coefficient of friction. Through a Design of Experiments methodology, the most influential factors affecting the coefficient of friction are identified. The results indicate that hard anodizing processes and applied load affect the coefficient of friction during wear testing as the main factor of influence. High values of the Unsaturation Number led to a high coefficient of friction at 5 N. Wavy-shaped profile tracks were detected at 10 and 15 N, leading to high specific wear rate values and the failure of the anodized layer.