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A multilayer film, composed by ZrN-Ag (20 nm) and Mo-S-N (10 nm) layers, combining the intrinsic lubricant characteristics of each layer was deposited using DC magnetron sputtering system, to promote lubrication in a wide-range of temperatures. The results showed that the ZrN-Ag/Mo-S-N multilayer film exhibited a sharp interface between the different layers. A face-centered cubic (fcc) dual-phases of ZrN and Ag co-existed in the ZrN-Ag layers, whilst the Mo-S-N layers displayed a mixture of hexagonal close-packed MoS2 (hcp-MoS2) nano-particles and an amorphous phase. The multilayer film exhibited excellent room temperature (RT) triblogical behavior, as compared to the individual monolayer film, due to the combination of a relative high hardness with the low friction properties of both layers. The reorientation of MoS2 parallel to the sliding direction also contributed to the enhanced anti-frictional performance at RT. At 400 °C, the reorientation of MoS2 as well as the formation of MoO3 phase were responsible for the lubrication, whilst the hard t-ZrO2 phase promoted abrasion and, consequently, led to increasing wear rate. At 600 °C, the Ag2MoO4 double-metal oxide was the responsible for the low friction and wear-resistance; furthermore, the observed transformation from t-ZrO2 to m-ZrO2, could also have contributed to the better tribological performance. [ABSTRACT FROM AUTHOR]

In this paper, TiN-Ni nanostructured composite films with different Ni contents are prepared using the magnetron sputtering method. The composition, microstructure, and mechanical properties of composite films are analyzed using an X-ray energy spectrometer (EDS), a scanning electron microscope (SEM), X-ray diffraction technology (XRD), a transmission electron microscope (TEM), and nanoindentation. All the films grow in a columnar crystal structure. There are only TiN diffraction peaks in the XRD spectrum, and no diffraction peaks of Ni and its compounds are observed. The addition of the Ni element disrupts the integrity of TiN lattice growth, resulting in a decrease in the grain size from 60 nm in TiN to 25 nm at 20.6% Ni. The film with a Ni content of 12.4 at.% forms a nanocomposite structure in which the nanocrystalline TiN phase (nc-TiN) is surrounded by the amorphous Ni (a-Ni) phase. The formation of nc-TiN/a-Ni nanocomposite structures relies on the good wettability of Ni on TiN ceramics. The hardness and elastic modulus of the film gradually decrease with the increase in Ni content, but the toughness is improved. The hardness and elastic modulus decrease from 19.9 GPa and 239.5 GPa for TiN film to 15.4 GPa and 223 GPa at 20.6 at.% Ni film, respectively, while the fracture toughness increases from 1.5 MPa·m1/2 to 2.0 MPa·m1/2. The soft and ductile Ni phase enriched at the TiN grain boundaries hinders the propagation of cracks in the TiN phase, resulting in a significant increase in the film's toughness. The research results of this paper provide support for the design of TiN-Ni films with high strength and toughness and the understanding of the formation mechanism of nanocomposite structures. [ABSTRACT FROM AUTHOR]

Nowadays, one of the most important challenges in the tribology field is to avoid the excessive consumption of soft metals such as Ag at elevated temperatures through the re-design of the self-lubricant films, to achieve the long-term lubricant under the temperature-cycling environments, for widely used in real industrial applications. This paper took up this challenge to develop a novel green film, by composing nano-particles Ag into the amorphous SiN x matrix using magnetron sputtering system, for achieving the long-term lubricant under the room temperature (RT)-500 °C temperature-cycling conditions. Results showed that the film exhibited a dual-phase of face-centered cubic (fcc) Ag and amorphous SiN x. An excellent RT-500 °C wear-resistance performance was observed for the films with the Ag content of 1.3–9.4 at.%, whilst the film at 15.8 at.% Ag exhibited the best anti-frictional performance (COF 0.3–0.5 for RT-500 °C conditions) at the cost of wear rate. The self-lubricant tribology behaviors under the RT-500 °C cycling conditions were mainly attributed by the synergism of: (1) mechanical properties, (2) excellent high-temperature chemical stability of SiN x matrix, and (3) the lubricant nature of Ag and its elevated temperature diffusion behaviors. [ABSTRACT FROM AUTHOR]

Composite Nb–Y–N films with different yttrium content (Y/(Nb + Y), at %) were prepared by reactive magnetron sputtering and the microstructure, oxidation resistance and mechanical properties were investigated. A combination of X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) analyses showed that the face-centered cubic (fcc) Nb–Y–N and hexagonal close-packed (hcp) Nb–Y–N coexisted in Nb–Y–N films. The adjunction of Y into NbN matrix led to a first increase in the hardness and then a subsequent decrease after reaching a summit with the value of ~31 GPa at 9.4 at % Y. The first increase of the hardness may be caused by the solid solution hardening and the increase of grain coarsening and tensile residual stress result in the succedent decrease of hardness. The oxidation resistance temperature of Nb-Y-N films increased gradually from about 500°C to about 760°C as the Y content in the film increases from 0 to 12.1 at %. [ABSTRACT FROM AUTHOR]

Industrial synthesis and application of green self-lubricant hard film have been considering as a hot spot in the field of surface engineering. In this paper, the Ag was added into the amorphous SiC matrix to deposit a series of Ag–SiC composite film with various Ag content using an industrial DC magnetron sputtering system, to enhancing the tribological properties for the real self-lubricant applications. Results showed that a dual-phase of fcc-Ag and amorphous SiC co-existed into the films regardless of Ag content. The accumulation of nano-particles of Ag could be detected in the amorphous matrix. The addition of soft Ag into the matrix gradually decreased the hardness from 21 ± 1 GPa for the binary SiC film to 7 ± 1 GPa for the composite film at 15.3 ± 0.8 at.% Ag, whilst it also dropped room temperature the average friction coefficient. Both the enhanced anti-friction property and the degradation of hardness attributed to the wear rate first dropping and then rising as a function of increase of Ag content and the lowest wear rate could be detected for the film at 4.3 ± 0.2 at.% Ag. • The SiC–Ag composite films were successfully deposited using an industrial magnetron sputtering system. • The adding Ag below 10 at.% kept a hardness of the film above 12 GPa. • The film at<10 at.% Ag exhibited both anti-frictional (COF<0.6) and wear-resistance (WR < 1 × 10−9 mm3/N.mm) properties. [ABSTRACT FROM AUTHOR]

Titanium nitride as a very representative ceramic film has been widely applied in cutting tools. Improvement the toughness and friction property of titanium nitride based films have been a research hotspot. In this paper, ruthenium was added into the titanium nitride brittle matrix and titanium ruthenium nitride composite hard films were synthesized using RF magnetron sputtering system and its crystal structure and room temperature tribological properties were investigated. The results showed that the addition of ruthenium above 1.3 at.% into the face-centered cubic (fcc) titanium nitride matrix exceeded the solid solubility limit and induced other phase of hexagonal close-packed (hcp) ruthenium. Addition of ruthenium into the titanium nitride matrix could enhance the fracture toughness, since it induced much more dislocations and interfaces. Compared with titanium nitride film, the content of adding ruthenium above 0.9 at.% reduced friction coefficient significantly without sacrificing the wear rate. Unlabelled Image • Titanium ruthenium nitride composite hard films were deposited using PVD system • The addition of ruthenium into the titanium nitride matrix enhanced the toughness. • Addition ruthenium into the titanium nitride matrix could improve the room temperature tribological properties. [ABSTRACT FROM AUTHOR]

Quaternary zirconium aluminum molybdenum nitride (Zr Al Mo N) composite films with different molybdenum content were deposited using reactive magnetron sputtering. The results showed that the films at <6.7 at.% molybdenum exhibited a single face center cubic (fcc) ZrN phase, while further incorporation of molybdenum led the film to exhibit a dual phase of fcc-ZrN and fcc-Mo 2 N. Zr Al Mo N films' room temperature friction coefficient decreased gradually due to the lubricant molybdenum and the formation of Mo 2 N phase in the film at > 6.7 at.% molybdenum. The room temperature wear rate first maintained its value of ∼3.5 × 10−7 mm−3 N−1 mm−1 at 0–8.6 at.% molybdenum and then dropped to ∼5.0 × 10−8 mm−3 N−1 mm−1 at 12.6 at.% molybdenum, while further increasing in molybdenum content results in the increase of wear rate. The roughness of the film and the appearance of fcc-Mo 2 N phase were considered as the main factors of the wear rate. For the tribological properties of the film at 13.8 at.% molybdenum, the increase in temperature could induce the main wear mechanism changing to oxidation wear. The change in the wear mechanism resulted in the decreasing in the wear rate as well as also led to the friction coefficient increased at first from RT to 500 °C and then started decreasing at further elevated temperature. • The incorporation of molybdenum into Zr Al N matrix decreased the room temperature friction coefficient. • Zr Al Mo N films at 34.0–40.5 at.% molybdenum exhibited excellent the room temperature wear resistance. • Zr Al Mo N film at 13.8 at.% molybdenum exhibited a friction coefficient of ∼0.5 at 700 °C against a alumina counterpart. [ABSTRACT FROM AUTHOR]

Abstract Niobium nitride and copper (NbN-Cu) composite films with different copper content (Cu/(Nb+Cu) = 0.6 at.%-24.8 at.%) were deposited using magnetron sputtering, and the microstructure and tribological properties of the films were investigated. The results showed that the films exhibited a mixture phase of face-centered cubic (fcc) NbN, hexagonal close-packed (hcp)NbN and fcc-Cu. The addition of copper below 6.0 at.% dropped both friction coefficient (μ) and wear rate (WR) sharply. A further increase in copper content decreased the μ furtherly, while the decreasing in μ took sacrifice of WR. The addition copper of 6.0 at.% into the niobium nitride matrix could broaden the niobium nitride film's effective service temperature to 400 °C. The lubricating copper (<200 °C) and the tribo-phases of copper oxide and niobium oxide remained the value of μ at ∼0.55 regardless of temperatures at the cost of the increase of WR. Highlights • The films exhibited a mixture phase of fcc-NbN, hcp-NbN, fcc-Cu. • The addition copper below 6.0 at.% could improve the room temperature tribological properties. • The addition copper of 6.0 at.% could broaden the film's effective service temperature to 400 °C. [ABSTRACT FROM AUTHOR]

A series of ZrN-Cu nano-composite films were deposited using the RF magnetron sputtering system. The microstructure, mechanical properties and tribological properties were investigated. The results showed that ZrN-Cu films were composed of face-centered cubice (fcc)-ZrN and face-centered cubic (fcc)-Cu. With the increase of Cu content, the hardness of ZrN-Cu composite film increased slowly first and then decreased rapidly. The maximum hardness value was 34.6GPa at 16at.% Cu. At room temperature, the coefficient of friction (Cof.) of ZrN-Cu films were lower than the ZrN film. When the content of Cu was lower than 39at.%, the wear rate of ZrN-Cu films were lower than the ZrN film. When the temperature of tribological testing was between 200-700C, the Cof. of ZrN-Cu films at 16at.% Cu were lower than ZrN film, while the wear rates were higher than the ZrN film. In summary, the addition of Cu improved the hardness and tribological properties of the ZrN-Cu film at room temperature, and decreased the Cof. of the ZrN-Cu during 200-700C. In the current study, different contents of Cu (up 43 at.%) were added to ZrN films and the microstructural using HRTEM was researched. Three lattice fringes (lattice spacings: ∼0.25 nm, ∼0.23 nm, 0.20 nm) were observed. These fringes correspond to fcc-ZrN (111), fcc-ZrN (200) and fcc-Cu (111), respectively, resulted that the ZrN-Cu films were composed of ZrN and Cu, and Cu dispersed in the ZrN-Cu films. [ABSTRACT FROM AUTHOR]

In this study, reactive magnetron sputtering was applied for preparing NbCN-Ag films with different Ag additions. Ag contents in the as-deposited NbCN-Ag films were achieved by adjusting Ag target power. The composition, microstructure, mechanical properties, and tribological properties were characterized using energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscopy (HRTEM), Raman spectrometry, nano-indentation, and high-temperature sliding wear tests. Results indicated that face-centered cubic (fcc) NbN, hexagonal close-packed (hcp) NbN and fcc Ag, amorphous C and amorphous CNx phase co-existed in the as-deposited NbCN-Ag films. After doping with 2.0 at.% Ag, the hardness and elastic modulus reached a maximum value of 33 GPa and 340 GPa, respectively. Tribological properties were enhanced by adding Ag in NbCN-Ag films at room temperature. When the test temperature rose from 300 to 500°C, the addition of Ag was found beneficial for the friction properties, showing a lowest friction coefficient of ~0.35 for NbCN-12.9 at.% Ag films at 500°C. This was mainly attributed to the existence of AgOx, NbOx, and AgNbOx lubrication phases that acted as solid lubricants to modify the wear mechanism. [ABSTRACT FROM AUTHOR]

W-Si-N films with various Si contents were deposited using a reactive magnetron system, and the film with the highest hardness, the lowest average friction coefficient (μ) and wear rate at room temperature (RT) was chosen to study the tribological properties at elevated temperature. Tribological properties of the film were performed using un-lubricated sliding tests against an alumina counterpart. Elevating the testing temperature from RT to 100 °C induced an intense skin plastic deformation, as a result, the μ increased rapidly and the wear rate decreased significantly. As the testing temperature was in the range of 100–200 °C, the surface deformation strengthening was induced furtherly, μ was further increased and the wear rate could not be calculated due the adhesive wear debris on the wear track. From 200 to 600 °C, the main wear mechanism changed to oxidation wear and the a lot of WO 3 tribo-film led to the decrease of μ. Wear rate increased gradually due to the accelerated oxidation of the film and the disappearance of surface deformation strengthening. [ABSTRACT FROM AUTHOR]

Composite TiN-Ag films with various Ag content (Ag/(Ti + Ag)) were deposited using reactive magnetron sputtering and the influence of Ag content on the crystal structure, mechanical and tribological properties were investigated. The result showed that face-centered cubic (fcc) TiN and fcc-Ag co-existed in the films and TiN had a columnar-growth and the Ag nanoparticles embedded in the boundary of columnar crystal. The hardness of TiN-Ag films initially increased gradually and reached an optimum value, and then decreased with an increase in Ag content in the films. The maximum hardness value was 29 GPa at 0.8 at.% Ag. The addition of Ag into TiN film could enhance the fracture toughness ( K IC ) and critical load ( L C1 ) of the films because the nanoparticle Ag provides a large volume fraction of grain boundaries. As Ag was added into TiN film, the average friction coefficient decreased from 0.78 at 0 at.% Ag to 0.20 at 41.1 at.% Ag; however, the wear rate of TiN-Ag films initially decreased and then increased, after reaching the minimum value of about 1.3 × 10 −7 mm 3 /(mm.N), at 0.8 at.% Ag. [ABSTRACT FROM AUTHOR]

W-Si-N composite films were deposited on both stainless steel and silicon wafers using a reactive magnetron system. The silicon content of the film was varied to evaluate the effect of silicon on films' elemental composition, microstructure, oxidation resistance, mechanical and tribological properties. These series of test were conducted using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM) analytical tools. The W-Si-N films showed a two-phase structure of solid solution face-centered cubic (fcc) W(Si)N x and an amorphous Si 3 N 4 . The thermal stability and the oxidation resistant temperature of W-Si-N films increased from about 380 °C at 0 at% Si to about 650 °C at 31.2 at% Si with the incorporation of Si into W 2 N matrix. The hardness of the films increased continuously from 26 GPa at 0 at% Si to 40 GPa at 23.5 at% Si which was due to solid strengthening and fine-grained strengthening. The silicon content affected the tribological properties of the film at room temperature but this was mainly influenced by the yield pressure, H/E ratio and elastic recovery, since lubricant tribo-film WO 3 was detected on all surfaces of the W-Si-N films. There was an initial gradual decrease in average coefficient of friction and wear rate until a minimum, but a further increase in silicon content resulted in increase in both friction coefficient and wear rates. The least coefficient of friction and wear rate values were 0.30 and 8.7 × 10 − 8 mm 3 /N·mm at 23.5 at% Si. [ABSTRACT FROM AUTHOR]

Composite Ti–Y–N films with various Y contents (0–7.8 at.%) were deposited by reactive magnetron sputtering to investigate the crystal structure, oxidation resistance, mechanical and tribological properties. A combination of X-ray diffraction (XRD), Raman spectroscopy and high resolution transmission electron microscopy (HRTEM) analyses showed that substitutional solid solution of Ti–Y–N is formed by substitution of Ti in TiN lattice by Y and all films exhibit a single-phase face-centered cubic (fcc) structure. The oxidation resistance temperature of Ti–Y–N films increased gradually from 560 °C at 0 at.% Y to 680 °C at 7.8 at.% Y. As Y was incorporated into TiN film, the hardness and elastic modulus of the films increased gradually from 21.7 GPa and 302 GPa at 2.9 at.% Y to 23.8 GPa and 316 GP at 7.8 at.% Y. The improvement of hardness was attributed to solid solution strengthening and fine-grain strengthening. Tribological properties of Ti–Y–N films performed using dry sliding friction and wear tests against Al 2 O 3 depended on Y content to a large extent. The average friction coefficient and wear rate of Ti–Y–N films decreased from about 0.32 and 7.7 × 10 − 7 m 3 /N·m at 2.9 at.% Y to about 0.20 and 6.8 × 10 − 7 m 3 /N·m at 7.8 at.% Y. Optical microscope and Raman spectroscopy measurements revealed that the decreasing amount of tribo-film TiO 2 and Y 2 O 3 detected on the surface of the wear tracks could lead to the friction coefficient curve stay constant and decrease the friction coefficients. Moreover, the incorporation of Y into TiN matrix induced the films to undergo a transition from serve wear to mild wear. [ABSTRACT FROM AUTHOR]

Recently, the chameleon thin films were developed with the purpose of adjusting their chemistry at self-mating interfaces in response to environmental changes at a wide temperature range. However, very few studies have focused on what state the lubricious noble metal exists in the films and the tribological properties at room temperature (RT). Composite NbN-Ag films with various Ag content (Ag/(Nb + Ag)) were deposited using reactive magnetron sputtering to investigate the crystal structure, mechanical and tribological properties. A combination of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM) analyses showed that face-centered cubic (fcc) NbN, hexagonal close-packed (hcp) NbN and fcc silver coexisted in NbN-Ag films. The incorporation of soft Ag into NbN matrix led to the hardness decrease from 29.6 GPa at 0 at.% Ag to 11.3 GPa at 19.9 at.% Ag. Tribological properties of NbN-Ag films performed using dry pin-on-disc wear tests against Al 2 O 3 depended on Ag content to a large extent. The average friction coefficient and wear rate of NbN-Ag films decreased as Ag content increased from 4.0 to 9.2 at.%. With a further increase of Ag content, the average friction coefficient further decreased, while the wear rate increased gradually. The optimal Ag content was found to be 9.2–13.5 at.%, which showed low average friction coefficient values of 0.46–0.40 and wear rate values of 1.1 × 10 −8 to 1.7 × 10 −8 mm 3 /(mm N). 3D Profiler and Raman spectroscopy measurements revealed that the lubricant tribo-film AgNbO 3 detected on the surface of the wear tracks could lead to the friction coefficient curve stay constant and decrease the average friction coefficients. The decrease of wear rate was mainly attributed to the lubricant tribo-film AgNbO 3 as Ag content increased from 4.0 to 9.2 at.%; with a further increase in Ag content, the wear rate increased with increasing Ag content in NbN-Ag films because a large amount of AgNbO 3 gathered on the surface of wear tracks and the predominant wear mechanism changed from abrasive wear to adhesive wear. [ABSTRACT FROM AUTHOR]

Ti–Mo–Si–N films with various Si content (0–17.2 at.%) were deposited by reactive magnetron sputtering and the effects of Si content on the microstructure, mechanical and tribological properties of Ti–Mo–Si–N films were investigated. The results showed that the face-centered cubic (fcc) interstitial solid solution of Ti–Mo–Si–N was formed by dissolution of Si into Ti–Mo–N lattice with the Si content in the range of 3.1–5.0 at.%. With a further increase in Si content, the films consisted of fcc-Ti-Mo-Si-N and amorphous Si 3 N 4 phases. The hardness and fracture toughness of Ti–Mo–Si–N films first increased and then decreased with the increase of Si content and the highest values were 34.5 GPa and 2.6 MP m 1/2 , respectively, at 5.0 at.% Si. The average friction coefficient and wear rate of Ti–Mo–Si–N films first decreased and then increased with the increase of Si content and the lowest values were 0.35 and 7.8 × 10 −8 mm 3 /Nmm, respectively, at 5.0 at.% Si. [ABSTRACT FROM AUTHOR]

Abstract: Mo–Al–N films with various Al content (3.7 at.%–18.3 at.%) were deposited by reactive magnetron sputtering and the effects of Al content on the microstructure, mechanical, oxidation resistance and tribological properties of Mo–Al–N films were investigated. The results showed that the synthesized Mo–Al–N films exhibited the face-centered cubic (fcc) structure with (111)-preferred orientation. The oxidation resistance of Mo–Al–N films increased with increasing Al content. The hardness and elastic modulus of Mo–Al–N films first increased and then decreased with increasing Al content in the films and the highest values were 32.6 GPa and 494 GPa, respectively, at 3.7 at.% Al. The films with an Al content in the range between 4.1 at.% and 9.5 at.% were found to be optimized for wear resistance applications, which showed low average friction coefficient values of 0.31–0.35 and wear rate of 3.6 × 10−9–8.1 × 10−9 mm3/Nmm. [Copyright &y& Elsevier]

A radio frequency magnetron sputtering system was used to add Ag into the TiCN matrix to improve its tribological properties at room and elevated temperatures. The results showed that the TiCN–Ag composite film with different Ag content was composed of four phases: face centered cubic (fcc) TiN phase, fcc-Ag phase, amorphous carbon, carbon nitride phases. Adding soft silver phase into the matrix decreased both hardness and elastic modulus. However, the addition of Ag improved the film's friction and wear properties at room and elevated temperatures due to the lubricating performance of Ag. • Films exhibited four phases of fcc-TiN, fcc-Ag, amorphous carbon and carbon nitride. • Increasing in the grain boundaries induced by adding Ag enhanced the critical adhesion load to 14.5 N. • Addition of Ag could improve the friction and wear properties at room and elevated temperatures. [ABSTRACT FROM AUTHOR]

Addition of soft Cu into hard Mo 2 N matrix could improve its wide-temperature self-lubricating property, but the consumption of the lubricating phase during the lubrication process sacrificed its wear-resistance property. In this paper, amorphous SiN x was added to encapsulate Mo 2 N and Cu phases using magnetron sputtering to improve the wear-resistance property. Results showed that Mo 2 N/Cu/SiN x films were mainly composed of face-centered cubic (fcc) solid solution of (Mo 1-x Si x) 2 N, fcc-Cu and amorphous (a) SiN x phases. Both dislocation increments in crystallites and micro-crack propagations in the interface were limited by the a-SiN x , and it resulted in the enhancement on the hardness from ~17 GPa for the film at 0 at.% silicon to ~30 GPa for the film at 3.3–5.7 at.% silicon. Addition of silicon below 5.7 at.% could improve the wear-resistance property at room temperature (RT). The film at 5.7 at.% silicon also exhibited an excellent wear resistance property after the RT-500 °C temperature cycling wear experiment. The a-SiN x phase, which encapsulated both (Mo 1-x Si x) 2 N and Cu phases, attributed to the improvement on both the RT wear-resistance property and RT-500 °C temperature cycling capability. [Display omitted] • The Mo 2 N/Cu/SiN x films exhibited a microstructure of (Mo 1-x Si x) 2 N and Cu nano-crystallites encapsulated with amorphous SiN x. • Hardness was enhanced from ~17 GPa at 0 at.% silicon to ~30 GPa at 3.3-5.7 at.% silicon. • The adding silicon below 5.7 at.% enhanced the wear-resistance performance at room temperature. • The film at 5.7 at.% silicon exhibited an excellent wear resistance property at RT-500 °C temperature cycling environments. [ABSTRACT FROM AUTHOR]

Novel multilayered films were engineered by integrating W 2 N and Ag-SiN x layers in a multilayer structure to obtain improved hardness and tribological properties. The films were fabricated by alternating magnetron sputtering, depositing 40 nm layers of W 2 N with varying thickness of Ag-SiN x layers varying in thickness from 4 to 20 nm. The effect of the increase thickness of the Ag-SiN x layers in the films microstructure and tribological properties were accessed. Tribological experiments were conducted at room temperature (RT), 500 °C, and RT-500 °C cycling conditions. The results revealed the production of a multilayered structure comprising single fcc-W 2 N layers interspersed with dual-phase layers consisting of fcc-Ag and amorphous SiN x phases. Tribological results indicated an improvement in the tribological performance with increase thickness of the Ag-SiN x layer up to 12 nm. The tribo-synergistic/combined action of both W 2 N and Ag-SiN x layers, along with the presence of layered lubricant tribo-phases of WO 3 and Ag 2 WO 4 , showcased the pivot role in reducing friction and enhancing wear resistance. The optimized multilayered film, featuring a 12 nm Ag-SiN x layer, demonstrated exceptional tribological properties under temperature-cycling from RT to 500 °C. [Display omitted] [ABSTRACT FROM AUTHOR]

Molybdenum nitride (Mo x N) film exhibited an excellent self-lubricating performance at room and elevated temperature, while its wear resistance was not very satisfactory. In this paper, silicon was added into the MoxN matrix to enhance the wear resistance and a series of Mo-Si-N films was deposited using magnetron sputtering system. Results showed that the incorporation of silicon into the Mo x N matrix in the argon and nitrogen atmosphere led to the formation of another phase of amorphous (a) Si 3 N 4 and the films exhibited a dual-phase of face-centered cubic (fcc) solid solution of (MoSi) x N and a-Si 3 N 4. Adding silicon <3.7 at.% dropped the wear rate (WR) at room temperature with the raising of friction coefficient (Cof.) due to the roughness reduction and hardness enhancement. Higher oxidation resistance temperature of the film at 3.7 at.% silicon resulted in a reduction of the MoO 3 tribo-phase and it improved the elevated temperature wear resistance, compared with the Mo x N film. • Adding Si of 12.4 at.% enhanced the oxidation resistance temperature to ~710 °C. • Addition Si < 3.7 at.% improved the wear resistance property at room temperature. • The elevated temperature wear rate of Mo 2 N/Si 3 N 4 film at 3.7 at.% Si was better than that of Mo 2 N. [ABSTRACT FROM AUTHOR]

Molybdenum nitride ceramic films, exhibiting excellent mechanical and frictional properties, have a great prospect for the application of high speed cutting tools and precision dies. However, the formation of lubricating tribofilm MoO 3 with a layer structure always weakens the wear-resistance. In this paper, copper was added into the molybdenum nitride matrix using RF magnetron sputtering system to improve the tribological properties at room temperature (RT) and elevated temperatures. The results showed that face-centered cubic (fcc) Mo 2 N, fcc-Cu and CuO phases co-existed in the molybdenum nitride and copper films. As the Cu/(Cu + Mo) ratio increased, RT average friction coefficient (Cof.) dropped gradually due to the lubricating Cu and CuO phases, while wear rate (WR) initially decreased and then increased gradually after reaching a minimum value of ~1.2 × 10−6 mm3/N·mm. WR at RT was mainly attributed by the soft lubricating phases, hardness and H / E ratio. The tribofilm changed from CuO to CuMoO 4 and MoO 3 as the testing temperature increased from 100 to 600 °C, this led to the drop in Cof. at the cost of WR. • Room temperature tribological properties were improved by Cu addition. • Adding copper reduced the friction coefficient at elevated temperatures. • Adding copper weakened wear-resistance at elevated temperatures. • Elevated temperature tribological properties were determined by tribofilms. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides such as molybdenum disulfide (MoS 2) were classified as excellent solid self-lubricant materials in vacuum or dry conditions. However, their poor mechanical and oxidation resistance properties limited their applications when used in humid air or at elevated temperature. In this paper, nitrogen was incorporated into the molybdenum disulfide matrix to synthesize the Mo–S–N films using RF magnetron sputtering system to improve above mentioned properties. The results showed the deposited nitrogen-free film was MoS x (x < 2), and due to its substoichiometry with respect to sulfur, both amorphous and crystalline state co-existed in MoS x film. Incorporation nitrogen into MoS x matrix induced the poor crystallinity and the formation of Mo–N, S–N and N–N bonds. All Mo–S–N films exhibit higher hardness and oxidation resistance temperature than that of MoS x mainly due to the Mo–N bonds. By comparison with MoS x film, all Mo–S–N films also had excellent tribological properties in the air at room temperature, 200 and 400 °C. Image 1 • All Mo–S–N films exhibited higher hardness and oxidation resistance temperature than that of MoS x film. • Addition of nitrogen into MoS x matrix could improve room temperature tribological properties in humid air significantly. • Addition of nitrogen broadened the film's effective service temperature range from 200 to 400 °C. [ABSTRACT FROM AUTHOR]

Mo2N films were synthesized using the reactive magnetron sputtering system in a mixture of argon and nitrogen, and the tribological properties were investigated at different testing temperatures against an Al2O3 counterpart. The relative intensity ratio (RIR) method was used to calculate the weight fraction of the tribo-film (MoO3) on the wear tracks of the films. The results showed that the average friction coefficient first increased from 0.30 at 25 °C to 0.53 at 200 °C, and then decreased to 0.29 at 550 °C, while the wear rate decreased from 2.1 × 10−6 mm3/Nmm at 25 °C to 5.3 × 10−7 mm3/Nmm at 200 °C and then increased to 3.1 × 10−5 mm3/Nmm at 550 °C. The weight fraction of tribo-film was mainly attributed to changes in the average friction coefficient and the wear rate. Besides this, the relative humidity also influenced the tribological properties at 25–200 °C. [ABSTRACT FROM AUTHOR]

Enhancing the tribological properties of hard ceramic coatings for high temperature applications is one of the hot topics in the solid lubricant field. In this paper, a series of Nb–V–N coatings with different V concentrations were deposited using RF magnetron sputtering system, and the crystalline structure, mechanical and tribological properties were investigated. Results showed that the Nb–V–N coatings regardless of V concentrations exhibited two phase fcc-NbN with V in solid solution and hcp-NbN phase. The hardness and elastic modulus of the coatings were enhanced by adding 5.3 at.% of V. The room temperature tribological properties of the coatings were improved by the addition of V well due to the enhanced mechanical properties and the nature excellent self-lubricant characteristics. The evaluation of main tribophase from the wear track at elevated temperatures from the self-lubricant V 2 O 3 at 400 °C to the V 2 O 5 at 800 °C, contributed to the stable and excellent anti-frictional properties of the coating with a V concentration of 12.4 at.%. However, the wear rate of the coatings drops gradually with the increase of V concentrations due to the large amount of soft but lubricant tribophases at elevated temperatures. • Magnetron sputtered Nb–V–N coatings exhibited dual-phase of fcc/hcp-NbN with V in solid solution. • The hardness of the coatings were enhanced to ∼33 GPa by adding 5.3 at.% of V. • Tribophase transformation from V 2 O 3 to V 2 O 5 contributed to enhanced the elevated temperatures anti- frictional properties. [ABSTRACT FROM AUTHOR]

Ti-W-Al-N films with various Al content (0 at.% ∼ 12.4 at.%) were deposited by reactive magnetron sputtering. The composition, microstructure, mechanical and tribological properties of Ti-W-Al-N films were investigated by EDS, XRD, HRTEM, SEM, Nano-indentation, Ball-on-disk tribometer. It is found that Ti-W-Al-N films consist of Ti-W-Al-N phase, Ti 2 N phase and W 2 N phase below 2.9 at.% Al. Ti 2 N phase disappears at 5.6 at.% Al and h-AlN phase forms at 12.4 at.% Al respectively. The hardness firstly increases and then decreases with increasing Al content and the highest hardness is 35.7 GPa at 8.7 at.% Al. At room temperature, the friction coefficient continuously increases, whereas the wear rate firstly decreases and then increases with increasing Al content. The lowest wear rate of 1.79 × 10 −8 mm 3 N −1 mm −1 is obtained at 8.7 at.% Al. As the temperature increases from room temperature to 700 °C, the friction coefficient firstly increases and then decreases, while the wear rate gradually increases. The tribological properties of the film depended on the testing temperatures significantly because the testing temperatures influenced the hardness, the tribo-films and wear mechanism of the film. [ABSTRACT FROM AUTHOR]

W 2 N-Cu films with different Cu content ranging from 0 to 6.22 at.% were deposited by reactive magnetron sputtering technique. The structure, mechanical and tribological properties were investigated by XPS, XRD, HRTEM, nano-indentation CSM, high-temperature ball-on-disc tribo-meter, Bruker 3D Profiler. The results indicated that the incorporation of copper did not affect the cubic structure. W 2 N-Cu films consist of W 2 N and Cu crystal phases. An addition of copper induced W 2 N crystallite size refinement accompanied by increase in hardness with a maximum at 0.9 at.% Cu. At room temperature, the friction coefficient of W 2 N-Cu films decreased gradually and the wear rate increased with increasing Cu content. At high temperatures, the friction coefficient of W 2 N-Cu films decreased with increasing Cu content but the wear rate increased. Overall, the results reveal that the friction properties of W 2 N-Cu films, in the temperature range of 25– 600 °C, can be improved by addition of a copper element, but the wear resistance failed to improve under same conditions. [ABSTRACT FROM AUTHOR]

Achieving the stringent demands of sustainable tribological industrial applications poses a significant challenge, particular in optimizing the self-lubricant performance of nitride-based films. This paper tackled this challenge by designing and depositing a series of ZrN-MoSN composite films with varying (Mo + S)/Zr ratios, employing RF magnetron sputtering, aimed to enhance the tribological properties through utilizing the high loading capacity of the ZrN matrix and the exceptional self-lubricating attributes of Mo-S-N additives. After conducting thorough investigations on the microstructure, and tribological properties, the results revealed that the dense columnar structured ZrN-MoSN composite films displayed a polycrystalline composition comprising fcc-ZrN and hcp-MoS 2 phases, intertwined with amorphous phases of Mo(SN) x and MoS 2 (N 2). (Mo + S)/Zr ratios below 1.08 exhibited a minor impact on the room temperature (RT) tribological properties, while higher ratios led to degradation on RT average friction coefficient (COF) and wear rate (WR). However, the synergistic effect of ZrN matrix and the tribo-phases of layered MoO 3 and hard ZrO 2 contributed to the significant enhanced 500 °C tribological properties, particularly with an optimized (Mo + S)/Zr ratio of 0.43. [Display omitted] • ZrN-MoSN composite films were fabricated by the magnetron co-sputtering technique. • The films exhibited a coexistence of fcc-ZrN, hcp-MoS 2 , Mo(SN) x and MoS 2 (N 2) phases. • Incorporating Mo-S-N in ZrN notably bolstered the 500 °C tribological properties. [ABSTRACT FROM AUTHOR]

In this paper, a series of TaCN composite films with different carbon content were deposited by the magnetron sputtering system and the microstructure, mechanical and tribological properties were investigated. The results showed that the deposited TaCN films exhibited a three-phase of face-centered cubic (fcc) Ta(C,N), hexagonal closed-packed (hcp) Ta(C,N) and amorphous CNx. With the increase of carbon content, the hardness of the TaCN films first increased and then decreased, after reaching a maximum of 33.1 GPa; the adhesion strength increased gradually; the coefficient of friction decreased monotonically and the wear property initially improved and then weakened at room temperature. The coefficient of friction of the TaCN film at 28.21 at.% carbon decreased first, then increased and then decreased again and its high-temperature wear rate first decreased slightly and then increased, as the temperature increased from room temperature (RT) to 600 °C. The TaCN film at 28.21 at.% carbon exhibited excellent an elevated-temperature tribological properties. [ABSTRACT FROM AUTHOR]

Vanadium nitride films exhibited excellent tribological properties due to the formation of Magnéli phases during the wear test, while the poor thermal stability, low hardness and high wear rate restricted it applied in cutting tool field. In this paper, aluminum was added into the vanadium nitride matrix in order to improve the thermal stability, mechanical and tribological properties. V-Al-N films with various Al content were deposited by reactive magnetron system and the effects of Al content on the micro-structure, oxidation resistance, mechanical and tribological properties of V-Al-N films were investigated. The results showed that V-Al-N films regardless of Al content exhibited a single face-centered cubic (fcc) structure. There was an increase in hardness when the content of Al was below 4.7 at.% with a corresponding decrease in room temperature friction coefficient (μ) and wear rate (WR). Rising Al content improved the oxidation resistance, while degraded the fracture toughness. The film at 4.7 at.% Al with highest hardness and lowest μ and WR was chosen to investigate its high temperature tribological properties. The rising temperature induced both the wear mechanism change and tribo-film vanadium oxides phase transition, and increased μ to 0.7 at 300 °C firstly and then dropped to 0.28 at 700 °C, while WR increased gradually. The film at 4.7 at.% Al was found to be optimized for cutting tool application. [ABSTRACT FROM AUTHOR]

A series of VCN-Ag films with different Ag content were deposited by the magnetron sputtering system. The microstructure, mechanical and tribological properties of VCN-Ag films were characterized by X-ray diffractometer (XRD), Raman spectrometer, transmission electron microscopy (TEM), scanning electron microscopy (SEM), nano-indentation and ball-on disc tribo-meter. The results showed that the deposited VCN-Ag films consisted of face-centered cubic (fcc) Ag, fcc-VCN, tetragonal (t) V 5 CN and amorphous graphite and CNx phases, and nano-crystalline Ag was dispersed in the films. The addition of Ag below 0.72 at.% into the film increased the hardness, however, the hardness decreased rapidly when the Ag content was increased furtherly. The initial introduction of Ag into the film led to the lowering of the film's room-temperature wear rate, nonetheless, the wear resistance deteriorated when the Ag content was further increased. However, the friction coefficient of the films at room temperature increased monotonically as the content of the Ag increased. As for elevated temperature tribological properties of the film at 3.03 at.% Ag, there was an initial increase in frictional values but, when the temperature was above 300 °C the frictional values declined. More so, the wear rate increased monotonically when the temperature increased from 100 °C to 500 °C. • VCN-Ag composite films were deposited by magnetron sputtering. • The hardness of VCN films was improved by Ag addition. • Adding Ag reduced the VCN films' friction coefficient and Room temperature wear rate. • VCN-3.03 at.% Ag composite film exhibited lower friction coefficient than VCN films at elevated temperature. [ABSTRACT FROM AUTHOR]