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- Mutual promotion on the mechanical and tribological properties of the nacre-like self-lubricant film designed for demanding green tribological applicationsPublication . Hongbo, Ju; Luan, Jing; Wang, Yiping; Bondarev, Andrey; Evaristo, Manuel; Geng, Yaoxiang; Xu, Junhua; Cavaleiro, Albano; Fernandes, Filipe; Fernandes, FilipeThe inverse relationship between the tribological and mechanical properties of environmentally friendly self-lubricant films, induced by the addition of soft lubricant agents that can diffuse quickly at elevated temperatures, has hindered the widespread use of these materials in industrial applications. This paper took this challenge to break through the above established relationship by developing novel nacre-like multilayered Mo2N–SiNx/Ag–SiNx self-lubricant films via an radio frequency (RF) magnetron sputtering system for real applications where harsh conditions at elevated temperatures exist. The multilayered films, deposited by alternating deposition of Mo2N–SiNx and Ag–SiNx modulation layers, exhibited three phases of face-centered cubic (fcc) Mo2N, fcc Ag and SiNx, where SiNx encapsulated the nano-crystalline Mo2N and Ag phases in each layer to successfully induce a “brick and mortar” nacre-like microstructure (in the area without the coherent structure). The epitaxy growth of the Ag–SiNx layers with thickness below 6 nm on the Mo2N template resulted in an extraordinary increase in both the hardness and elastic modulus, which was able to prevent severe degradation of the mechanical properties caused by the addition of Ag. The room-temperature anti-friction property could be enhanced by increasing the Ag–SiNx layer thickness due to the excellent lubricant nature of Ag, which acts in synergy with Mo2N, while the wear rate below 4×10−8 mm3/(N·mm) was due to the high mechanical strength. The tribological properties at 600 °C also benefited from the interlocked multilayered architecture, which allowed an extreme low friction coefficient of ~0.12 and a negligible wear rate (WR). This behavior was attributed to the synergism between the lubricant action of Ag and Mo2N and the tribo-phase transformation from Ag2Mo4O13 to Ag2MoO4.
- Real-time temperature monitoring during titanium alloy machining with cutting tools integrating novel thin-film sensorsPublication . Fernandes, Filipe; Martins, Bruno; Patacas, Carlos; Cavaleiro, Albano; Faia, PedroThis study explores the integration of titanium aluminum nitride (TiAlN) and zirconium aluminum nitride (ZrAlN) thin-film sensors into cutting tools for real-time temperature monitoring during machining of Ti6Al4V titanium alloy. These sensors, integrated into a multilayer coating for electrical and wear shielding, were deposited directly onto the tool surfaces and calibrated for temperatures up to 750 °C. Due to the integration into the multilayer coating, the sensors exhibit different β sensitivities across the temperature range, ranging from 108 to 825 K for TiAlN and from 950 to 6681 K for ZrAlN. The cutting tests conducted under various cutting conditions, such as cutting speed, feed rate, depth of cut, and cooling, revealed the influence of these parameters on the cutting temperature. Our findings indicate that the sensor position in the tool’s rake face is fundamental for measuring the cutting temperature. The study introduces an innovative tool connector for integration and signal retrieval of the cutting tool in a “plug-and-play” fashion, compatible with industry standards. Additionally, implementing wireless data transmission for real-time and in-situ temperature monitoring offers a pathway for integrating smart cutting tools into modern manufacturing environments, aligning with Industry 4.0.
- Microstructure, Mechanical, and Tribological Properties of Mo2N/Ag-SiNx Nanomultilayers with Varying Modulation PeriodsPublication . Fernandes, Filipe; Luan, Jing; Wang, Lei; Dong, Songtao; Ferreira, Fábio; Mo, Changpan; Cavaleiro, Albano; Ju, Hongbo; Kiryukhantsev-Korneev, PhilippThe multilayered Mo2N/Ag-SiNx self-lubricant films were designed and deposited using a DC (Direct Current) magnetron sputtering system under mixed gas atmosphere of N2 and Ar. The modulation ratio (thickness ratio of Mo2N to Ag-SiNx) was fixed at 2:1, while the modulation periods (thickness of Mo2N and its adjacent Ag-SiNx layer) were set at 20, 40, and 60 nm. The results indicated that all multilayer films, regardless of modulation period, exhibited a combination of face-centered cubic (fcc) and amorphous phases. Specifically, fcc-Mo2N was detected in the Mo2N layers, while fcc-Ag and amorphous SiNx co-existed in the Ag-SiNx layers. The multilayered architecture induced residual stress and interface strengthening, resulting in hardness values exceeding 21 GPa for all films. Compared to Mo2N and Ag-SiNx monolayer films, the multilayer structure significantly enhanced tribological properties at room temperature, particularly in terms of wear resistance. The Mo2N/Ag-SiNx multilayer films exhibit ~25% lower friction than Ag-SiNx, ~3% lower than Mo2N, and achieve remarkable wear rate reductions of ~71% and ~85% compared to Ag-SiNx and Mo2N, respectively, demonstrating superior tribological performance. The synergistic effects of both modulation layers and relative high hardness were key factors contributing to the enhanced tribological behavior.
- Performance evaluation of TiAlSiN and TiSiN/TiSiVN coatings during high-speed dry turning of AISI 316 L considering the role of vanadium-based tribo-oxidesPublication . Fernandes, Filipe; Kumar, Ch. Sateesh; Lacalle, Luis Norberto López de; Cavaleiro, Albano; Cavaleiro, Diogo; Kalin, Mitjan; Prajapati, RamanandThis study investigates the tribo-mechanical performance of uncoated, TiAlSiN-coated, and TiSiN/TiSiVN multilayer-coated Al2O3/SiC ceramic tools during dry turning of AISI 316 L austenitic steel across three successive passes at varying cutting speeds. Key machining outputs, including cutting forces, surface roughness, cutting temperature, and tool wear (flank and crater), were analyzed with a focus on oxide formation and selflubricating mechanisms. The TiSiN/TiSiVN-coated tool exhibited the most favorable performance, showing only ~15 % increase in cutting force across passes, ~9 % improvement in flank wear resistance compared to TiAlSiN, and ~ 17 % lower wear progression relative to the uncoated tool at 350 m/min. Surface roughness and cutting temperature trends further confirmed the coating’s superiority, attributed to the formation of V₂O₅ tribo-oxides, which reduce friction and thermal degradation. EDS and SEM analyses validated the wear protection mechanisms, highlighting the adaptive role of vanadium-based layers in mitigating adhesion and thermal fatigue. The results establish TiSiN/TiSiVN as a promising candidate for high-speed dry machining due to its superior mechanical-chemical synergy and wear resistance.
- Tribological Comparison of Coatings Produced by PVD Sputtering for Application on Combustion Piston RingsPublication . Ferreira, Ney Francisco; Neis, Patric Daniel; Fernandes, Filipe; Poletto, Jean Carlos; Yaqub, Talha Bin; Cavaleiro, Albano; Vilhena, Luís; Ramalho, AmílcarThis article compares the tribological performance of coatings produced by PVD sputtering. Transition metal dichalcogenide (TMD) coatings doped with carbon (WSC and MoSeC) and nitrogen (WSN and MoSeN) and a conventional diamond-like carbon (DLC) coating are compared. The tribological evaluation was oriented towards the use of coatings on piston rings. Block-on-ring tests in a condition lubricated with an additive-free polyalphaolefin (PAO 8) and at temperatures of 30, 60, and 100 °C were carried out to evaluate the coatings in boundary lubrication conditions. A load scanner test was used to evaluate dry friction and scuffing propensity. In addition to WSN, all other TMD coatings (WSC, MoSeC, and MoSeN) exhibited lower friction than DLC in dry and lubricated conditions. The study reveals that WSC, among TMD coatings, offers promising results, with significantly lower friction levels than DLC, while demonstrating reduced wear and a lower risk of metal adhesion. These findings suggest that WSC may be a viable alternative to DLC in piston rings, with potential benefits for reducing fuel consumption and increasing engine durability.
- Can ZrAlN thin films be used as thermistor sensors for temperature assessment?Publication . Martins, Bruno; Patacas, Carlos; Cavaleiro, Albano; Faia, Pedro; Bondarchuk, Oleksandr; Fernandes, FilipeThe electrical characteristics and conduction mechanisms of ZrAlN thin films for their potential use as thermistor sensors were assessed. Various compositions of Zr1-xAlxN were synthesized by sputtering and studied up to 200 °C to understand their sensitivity and applicability. Among the compositions studied, the ones with x = 0.34 and x = 0.46 showed the highest sensitivities, reaching values close to 3000 K. However, the thermo-resistive properties exhibited by these compositions limited their utilization above 100 °C. Zr1-xAlxN film compositions with x higher than 0.46 showed amorphous structures and were found to be insulative. Composition with x = 0.26, within the cubic phase, showed the most promising electrical properties regarding temperature sensing in the studied range. XPS analysis of this composition confirmed the presence of Zr-N and Al-N bonds, with a Zr3+ oxidation state, which suggests the availability of a free electron contributing to the electrical conduction. Impedance measurements performed at different temperatures for this composition revealed the dominant role of the grain boundaries in the conduction mechanism, based upon electron hopping between grains, overcoming the energy barrier imposed by the grain boundaries. ZrAlN thin films demonstrate negative temperature coefficient (NTC) thermistor behavior, expanding their applications beyond protective coatings to temperature monitoring.
- Influence of 1-Ethyl-3-methylimidazolium Diethylphosphate Ionic Liquid on the Performance of Eu- and Gd-Doped Diamond-like Carbon CoatingsPublication . Sadeghi, Mohammadamin; Omiya, Takeru; Fernandes, Filipe; Vilhena, Luís; Ramalho, Amílcar; Ferreira, FábioA composite lubricating system that combines solid and liquid lubrication can create a synergistic effect by leveraging the strengths of both types of lubricants. Solid lubrication coatings possess advantageous load-bearing abilities and exhibit low volatility. By adopting this approach, the system retains the merits of solid lubrication while simultaneously harnessing the advantages of liquid lubrication. The unique properties of diamond-like carbon coatings (DLCs) offer the potential to create binding locations for lubricant additives by introducing dopant elements that have a high affinity with additives. In the present work, the combined use of europium-doped diamond-like carbon (Eu-doped DLC) with varying atomic concentrations of the dopant element (1.7 at. % and 2.4 at. %) and gadolinium-doped diamond-like carbon (Gd-doped DLC) with different atomic concentrations of the dopant element (1.7 at. % and 2.3 at. %) was studied alongside a pure DLC coating and the incorporation of an ionic liquid (IL) additive in a tribological block-on-ring system. The focus was on the 1-Ethyl-3-methylimidazolium diethylphosphate ionic liquid with a concentration of 1 wt. % in polyalphaolefin (PAO) 8. Among the investigated pairs, the coefficient of friction (CoF) of 1.7 at. % Eu-doped DLC coupled with the IL was the smallest in boundary, mixed, and elastohydrodynamic lubrication regimes. Quantification of wear was challenging due to minimal and localized wear on the DLC coating surfaces. The decrease in friction within the boundary lubrication regime underscores the promise of mechanical systems that integrate 1.7 atomic percent Europium-doped diamond-like carbon coatings with ionic liquids (IL). This study presents a compelling avenue for future scholarly exploration and research efforts focused on reducing friction and improving the efficiency of moving components, particularly in situations where tribological properties exert a substantial influence
- Comparative analysis of microstructural, compositional, and grazing incidence characteristics of oxide scale on 316L steel: SLM vs. wrought conditionsPublication . Sehat, Alireza; Hadi, Morteza; Isfahani, Taghi; Fernandes, Filipe; Fernandes, FilipeThe aim of this research is to compare the oxidation behavior and characteristics of oxide scale of 316L steel produced by two methods: selective laser melting (SLM) and conventional casting and forming (wrought). To this end, the initial composition and microstructure of samples produced by those methods were first studied. Thermogravimetric analysis (TGA) and long-term isothermal oxidation tests were carried out on the samples and the oxidation kinetics were compared. The oxidized samples were then examined by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and grazing incidence X-ray diffraction (GIXRD). The results indicated that in the temperature range of 600 °C–900 °C, the oxidation resistance of the SLM alloy is lower than that of the wrought alloy, especially at 800 °C. This is attributed to the combined effect of: i) smaller grain size due to the rapid solidification in the SLM alloy that increases the paths of oxygen penetration, ii) lower presence of chromium and manganese elements in the oxide layer and iii) preferential growth of iron oxide in the form of hillocks on the surface. Surface and cross-section analysis of the oxide layers show that iron oxide is dominant on the surface of the SLM sample at temperatures of 600 °C and 800 °C, and at 800 °C its extended hilly growth leads to significant spallation of the oxide scale and an exponential increase in the oxidation rate. However, at 900 °C, with the formation of a continuous oxide layer containing Fe2MnO4 and CrMnO4, the oxidation rate significantly decreases in both alloys.
- Deciphering the mechanical strengthening mechanism: Soft metal doping in ceramic matrices: A case study of TiN-Ag filmsPublication . Luan, Jing; Kong, Fanlin; Xu, Junhua; Fernandes, Filipe; Evaristo, Manuel; Dong, Songtao; Cavaleiro, Albano; Ju, Hongbo; Fernandes, FilipeSoft metals have been widely added into ceramic-based films for fully meeting the demanding requirements of green tribological applications. However, the resulting considerable increase of the mechanical strength by adding a soft metal below 5 at.%, which reversed the rule-of-mixture, was still not fully revealed. In this paper, a case study of TiN-Ag films was carried out to investigate the strengthening mechanism induced by adding soft metal in TiN-Ag composite/multilayered films deposited by magnetron sputtering. The results showed that dual-phases of fcc-TiN and fcc-Ag co-existed in the composite films with the Ag particles embedded in the matrix. In some areas of the Ag particles, with a size below 4 nm, epitaxial growth with the TiN template was detected, which obliged the lattice to be distorted and shrunken. Consequently, both hardness and elastic modulus were enhanced from 21 and 236 GPa, for the reference TiN film, to 26 and 323 GPa for the TiN-Ag composite film with 2.4 at.% Ag. The possibility of having the epitaxial growth of Ag within TiN were also confirmed by designing a TiN/Ag multilayered film with an Ag layer thickness of ∼3 nm.
- Expanding the applications of the wear-resistant titanium aluminum nitride thin-film to include temperature sensingPublication . Martins, Bruno; Patacas, Carlos; Cavaleiro, Albano; Faia, Pedro; Zorro, Fátima; Carbo-Argibay, Enrique; FGerreira, Paulo J.; Fernandes, Filipe; Fernandes, FilipeThis study investigates an approach to temperature sensing by integrating Titanium Aluminum Nitride (TiAlN), originally engineered for wear and corrosion applications, as a temperature sensor within a multilayered thin film system. A nitride multilayer system was developed by physical vapor deposition (PVD) using a single four-target magnetron sputtering chamber; intermediate vacuum interruption steps were employed for masking procedures. The multilayer architecture design aimed to provide the sensor layer with mechanical protection and electrical shielding. Structural and electrical characterization of the TiAlN single layer revealed semiconductor behavior and stable electrical resistance up to 750 °C, with minimal signal stabilization requirements. Despite the higher Al content, the TiAlN temperature sensor exhibited a cubic crystal structure characterized by diffuse nanolayers, resulting from a two-fold rotational deposition and target configuration. A detailed examination of the multilayer system cross-section containing the TiAlN sensor was conducted using scanning transmission electron microscopy (STEM). The analysis revealed its columnar morphology with the presence of typical PVD growth defects, including voids and droplets. While the presence of these defects may impact the electrical characteristics of the sensor, the selected experimental conditions effectively maintained the structural integrity of the multilayer system despite the vacuum interruptions caused by masking procedures. Validation experiments confirmed the functionality of the multilayer system for temperature measurements up to 400 °C. The signal acquisition system addressed room temperature resistance variations and low sensitivity (thermistor coefficient ∼100 K), resulting in a measured error of approximately 6%. This study demonstrates promising results of TiAlN as a temperature sensor within a multilayered system, expanding its range of potential applications.