Percorrer por autor "Kalin, Mitjan"
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- Mutually enhanced mechanical and tribological properties in magnetron sputtered Mo2N/Ag-SiNx self-lubricating multilayered films via epitaxial growth designPublication . Fernandes, Filipe; Luan, Jing; Wang, Lei; Dong, Songtao; Choukourov, Andrei; Yang, Junfeng; Kalin, Mitjan; Cavaleiro, Albano; Ju, Hongbo; Vincenzini, P.Achieving simultaneous enhancement of both mechanical and self-lubricating properties by incorporating soft lubricants into nitride films has been a longstanding challenge in the development of solid lubricant materials. This paper introduced a novel approach to overcome this challenge by developing coherent-structured Mo2N/Ag-SiNx multilayered films using radio frequency (RF) magnetron sputtering. The multilayer films were designed with a fixed modulation period of 30 nm, while the modulation ratio (γ) was varied from 1:9 to 1:1. The Mo2N layers exhibited a single fcc-Mo2N phase, while the Ag-SiNx layers formed a dual-phase structure comprising fcc-Ag nanoparticles embedded in an amorphous SiNx matrix. At a modulation ratio of 1:9, the Ag-SiNx layer epitaxially grew on the Mo2N template, resulting in a coherent structure. This coherent structure significantly enhanced both the hardness and elastic modulus, reaching approximately 36 GPa and 230 GPa, respectively. The improved wear resistance at room temperature can be attributed to the coherent strengthening effect, which not only elevated the film's hardness but also eliminated sharp interfaces between modulation layers, thereby reducing crack initiation sites. In temperature-cycling tribo-testing from room temperature to 600 °C, the film with a γ of 1:9 maintained a stable coefficient of friction around 0.2, except during the initial room temperature, where it was 0.4. The wear rate could not be accurately calculated due to the adhered tribolayer on the top of the wear track following the initial tribo-test at 600 °C. The excellent tribological properties across temperature cycles were attributed to the synergistic lubricant characteristics of both layers and the formation of self-lubricating tribo-phases. The optimized Mo2N/Ag-SiNx multilayered films provide an effective balance of lubrication and mechanical stability under extreme conditions, making them highly promising for high-performance engineering applications.
- Nitrogen alloyed MoSe2 coatings – Role of optimized morphology, structure and mechanical properties on diverse environment sliding performancePublication . Fernandes, Filipe; Yaqub, Talha Bin; Nadeem, Irfan; Yaqoob, Khurram; Kalin, Mitjan; Cavaleiro, AlbanoTransition metal dichalcogenide (TMD) coatings are gaining increasing interest among the scientific community as eco-friendly solutions for reducing friction, improving energy conservation, and lowering carbon footprints. N-alloyed MoSe2 coatings (MoSeN), a subset of TMDs, remain largely underexplored, with no research on their frictional performance across various sliding environments. Herein, an in-depth analysis of DC-magnetron sputtered MoSeN coatings is presented, with N content varying from 0 to 42 at%. Investigation of composition, morphological features, crystal structure, mechanical strength and sliding performance are accessed. Our findings revealed that N additions resulted in increased compactness, amorphous structure and hardness of ∼4.6 GPa, and these improvements remained consistent despite compositional variations. The sliding competency was evaluated under six different conditions, revealing promising results in ambient-air and dry-N2 atmospheres at room conditions and 100 °C. At 200 °C, the sliding performance in ambient-air was better than dry-N2. Friction coefficient for N-alloyed coatings was relatively close, ranging between 0.03 and 0.06, except for a dry-N2 environment at 200 °C. Nevertheless, wear rate showed slight variations, with higher values observed in dry-N2 at 100 °C and 200 °C but remained within a specific range of 1–7 × 10−7 mm3/Nm for all other conditions. This study highlights the potential of MoSeN coatings to be scaled for industrial applications, offering a roadmap for reducing the inherent limitations of PVD sputtering.
- 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.