The structure and mechanical and tribological properties of TiBCN nanocomposite coatings

TiBCN nanocomposite coatings were deposited in a closed field unbalanced magnetron sputtering system using pulsed magnetron sputtering of a TiBC compound target with various Ar/N₂ mixtures. TiBCN coatings were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, nanoindentation, Rockwell C indentation and ball-on-disk wear tests. The coatings with a nitrogen content of less than 8 at.% exhibited superhardness values in the range of 44–49 GPa, but also showed poor adhesion and low wear resistance. Improvements in the coating adhesion, H/E ratio and wear resistance were achieved together with a decrease in the coating hardness to 35–45 GPa as the N content in the coatings was increased from 8 to 15 at.%. The microstructure of the coatings changed from a nano-columnar to a nanocomposite structure in which 5–8 nm nanocrystalline Ti(B,C) and Ti(N,C) compounds were embedded in an amorphous matrix consisting of BN, free carbon and CN phases. With a further increase in the N content in the coatings to levels greater than 20 at.%, the inter-particle spacing of the nanocrystalline compounds increased significantly due to the formation of a large amount of the amorphous BN phase, which also led to low hardness and poor wear resistance of the TiBCN coatings.     

Mechanical properties and oxidation resistance of CrAlN/BN nanocomposite coatings prepared by reactive dc and rf cosputtering

CrAlN/BN nanocomposite coatings were deposited through reactive cosputtering, i.e., pulsed dc and rf sputtering, of CrAl and h-BN targets, respectively. X-ray diffraction (XRD) and selected area electron-diffraction (SAED) analysis indicated that the CrAlN/BN coating consists of very fine grains of B1 structured CrAlN phase. With an increasing BN volume fraction of over 8 vol.%, the nanocrystalline nature of the grains is revealed through a dispersion of fine grains in the CrAlN/BN coating. A cross-sectional observation using a transmission electron microscope (TEM) clarified that the coating demonstrating the highest level of hardness has a fiber-like structure consisting of grains that are ~ 20 nm in width and ~ 50 nm in length. X-ray photoelectron spectroscopy (XPS) analysis revealed that the coating consists mainly of CrAlN and h-BN phase. The indentation hardness (H_IT) and effective Young's modulus (E*) of the coatings increased with the BN phase ratio, reaching a maximum value of ~ 46 and ~ 440 GPa at ~ 7 vol.% of BN phase; it then decreased moderately to ~ 40 and ~ 350 GPa at 18 vol.% of BN, respectively. Furthermore, CrAlN/BN coatings showed superior oxidation resistance compared with CrAlN coatings. After annealing at 800 °C in air for 1 h, the indentation hardness of CrAlN coatings decreased to 50% of the as-deposited hardness; in contrast, the hardness of CrAlN/BN nanocomposite coatings either stayed the same or increased, attaining a value of about 46 GPa. After annealing at 900 °C for 1 h, the hardness of all the coatings decreased to about 40%.     

Effect of C2H2 gas flow rate on synthesis and characteristics of Ti–Si–C–N coating by cathodic arc plasma evaporation

The influences of C₂H₂ gas flow rate on the synthesis, microstructure, and mechanical properties of the Ti–Si–C–N films were investigated. Quaternary Ti–Si–C–N coatings were deposited on WC-Co substrates using Ti and TiSi (80:20 at.%) alloy target on a dual cathodic arc plasma evaporation system. The Ti–Si–C–N coatings were designed with Ti/TiN/TiSiN as an interlayer to enhance the adhesion strength between the top coating and substrate. The Ti–Si–C–N coatings were deposited under the mixture flow of N₂ and C₂H₂. Composition analysis showed that as the C₂H₂ gas flow increased, the Ti, Si and N contents decreased and the carbon content increased in the coatings. The results showed the maximum nanohardness of approximately 40 GPa with a friction coefficient of 0.7 was obtained at the carbon content of 28 at.% (C₂H₂ = 15 sccm). However, as the C₂H₂ gas flow rate increased from 15 to 40 sccm (carbon content from 25.2 to 56.3 at.%), both the hardness and friction coefficient reduced to 20 GPa and 0.3, respectively. Raman analysis indicated the microstructure of the deposited coating transformed from Ti–Si–C–N film to TiSi-containing diamond-like carbon films structure, which was strongly influenced by the C₂H₂ flow rate and is demarcated at a C₂H₂ flow of 20 sccm. The TiSi-containing diamond-like carbon films reveal low-friction and wear-resistant nature with an average friction coefficient between 0.3 and 0.4, lower than both TiSiN and Ti–Si–C–N films.     

Erosion performance and characterization of nanolayer (Ti,Cr)N hard coatings for gas turbine engine compressor blade applications

(Ti,Cr)N nanolayer coatings were deposited on Ti–6Al–4V, 17-4PH and Inconel 718 substrates using cathodic arc physical vapor deposition for improved erosion and corrosion resistance. Coating corrosion performance was highly dependent on the coating thickness and packing factors and correlated with increased chromium content within the (Ti,Cr)N nanolayer coatings. The change in cathode current predominantly affected coating thickness and the bias affected the packing factor. Erosion tests of the coated and uncoated substrates at both 30° and 90° erodent impingement angles were conducted using angular aluminum oxide media at particle velocities up to 145 m/s. Chromium evaporator current and substrate bias were varied to change film stoichiometry and microstructure for erosion performance evaluation. When chromium evaporator current was varied, the increase in chromium content led to an increase in binary CrN phase volume and a decrease in TiN phase volume. The increase in CrN phase volume decreased both hardness and erosion performance at both impingement angles. Lower bias values resulted in better erosion performance. At 30° erodent impingement, all coated samples outperformed the uncoated substrate; whereas, for 90° impingement, only coatings deposited at low bias values (? 25 V, ? 50 V, and ? 100 V) and high Ti:Cr ratios (> 2.4) outperformed the uncoated substrate. The primary coating failure mechanism was microchipping.     

Microstructure,hardness, toughness and oxidation resistance of Al2O3–ZrB2 composite with different Ti percentages prepared by in-situ SHS dynamic compaction

Effect on microstructure, hardness, modulus, fracture toughness and oxidation behaviour of Al₂O₃–ZrB₂ composite with different percentages of Titanium as diluents during the SHS reaction has been studied. It was observed that Ti addition leads to formation of different phases such as TiB₂, ZrO_2, TiB besides ZrB₂ and Al₂O₃. The hardness and modulus were found to be around 21 GPa and 350 GPa, respectively for 10 wt.% Ti addition in dynamic depth indentation. Oxidation study of the sample having 25 wt.% Titanium showed no significant change in phase and mechanical properties after 700 °C oxidation. The toughness of 20 wt.% Ti sample showed highest fracture toughness.     

Advantages of nanocomposite coatings deposited by high power pulse magnetron sputtering technology

Recent advantages in PVD coatings for cutting tools enable high speed and dry machining with superior cutting parameters in commercial manufacturing sectors. For this reason hard coatings with high oxidation resistance and thermal stability are used for economically justifiable machining. In this regard nc-(Ti,Al)N/a-Si₃N₄ films were sputtered on tungsten carbide cutting tools and WC/Co samples by using the high power pulse magnetron sputtering (HPPMS) technology. Coating composition, microstructure and applied properties were investigated by using X-ray diffraction, scanning electron microscope and nanoindentation. The hardness value was about 29 GPa for a Si content of 3.3 at.%. The grain size was about 6 nm. As this study focuses on the thickness uniformity of the coatings, SEM pictures of the cross-section have been taken around the cutting edge to determine the deposition rate and the film growth. The coatings morphology has been compared to middle frequency and direct current sputtered nanocomposite (Ti,Al,Si)N films. The results demonstrate the enhanced HPPMS coatings properties, including a denser structure, a smoother surface and a favourable thickness uniformity.     

Chromium carbide–CNT nanocomposites with enhanced mechanical properties

Chromium carbide is widely used as a tribological coating material in high-temperature applications requiring high wear resistance and hardness. Herein, an attempt has been made to further enhance the mechanical and wear properties of chromium carbide coatings by reinforcing carbon nanotubes (CNTs) as a potential replacement of soft binder matrix using plasma spraying. The microstructures of the sprayed CNT-reinforced Cr₃C₂ coatings were characterized using transmission electron microscopy and scanning electron microscopy. The mechanical properties were assessed using micro-Vickers hardness, nanoindentation and wear measurements. CNT reinforcement improved the hardness of the coating by 40% and decreased the wear rate of the coating by almost 45–50%. Cr₃C₂ reinforced with 2 wt.% CNT had an elastic modulus 304.5 ± 29.2 GPa, hardness of 1175 ± 60 VH_0.300 and a coefficient of friction of 0.654. It was concluded that the CNT reinforcement increased the wear resistance by forming intersplat bridges while the improvement in the hardness was attributed to the deformation resistance of CNTs under indentation.     

Microstructure evolution of Ti–Si–C–Ag nanocomposite coatings deposited by DC magnetron sputtering

Nanocomposite coatings consisting of Ag and TiC_x (x < 1) crystallites in a matrix of amorphous SiC were deposited by high-rate magnetron sputtering from Ti–Si–C–Ag compound targets. Different target compositions were used to achieve coatings with a Si content of ～13 at.%, while varying the C/Ti ratio and Ag content. Electron microscopy, helium ion microscopy, X-ray photoelectron spectroscopy and X-ray diffraction were employed to trace Ag segregation during deposition and possible decomposition of amorphous SiC. Eutectic interaction between Ag and Si is observed, and the Ag forms threading grains which coarsen with increased coating thickness. The coatings can be tailored for conductivity horizontally or vertically by controlling the shape and distribution of the Ag precipitates. Coatings were fabricated with hardness in the range 10–18 GPa and resistivity in the range 77–142 μΩ cm.     

Characterization studies of pulse magnetron sputtered hard ceramic titanium diboride coatings alloyed with silicon

The composition, structure and mechanical properties of pulsed-DC unbalanced magnetron sputtered Ti–Si–B thin films—hard coatings with the potential for excellent thermal stability and oxidation resistance—are investigated and reported in this paper. Fully dense, hard (19–37 GPa) Ti–Si–B coatings were deposited at substrate bias voltages (V_s) ranging from floating potential to −150 V which resulted in substrate temperatures of ∼90–135 °C. We found that variation of substrate biasing conditions critically affected film composition, structure and resultant mechanical properties. For instance, concentration of Si in films decreased from 18.4 at.% to 3.8 at.% as V_s was increased from floating potential to −150 V; composition profile analysis of the near-surface region of films (0–10 nm) revealed them to be rich in Si with significant differences among specimens produced at different substrate bias conditions. Variation of substrate biasing conditions provided coating structures that ranged from completely amorphous at floating substrate potential to nanocrystalline at V_s = −50 to −100 V and crystalline nanocolumnar at V_s = −150 V. We found that each of the structures obtained exhibited different specific values of hardness and elastic modulus, which is also in a good agreement with results reported for other coatings possessing similar micro- and nano-structures. Film structure was analyzed in detail by conventional and analytical transmission electron microscopy. Coatings that exhibited the highest values of hardness (37 GPa) were found to possess features such as crystalline nanocolumnar grains a few nanometres in diameter and disordered intergranular regions of different chemical composition, thus qualifying as nanocomposite films. Results of this work allowed relationships to be drawn between deposition parameters and Ti–Si–B coating composition, structure and mechanical properties. Qualitatively similar relationships are also expected for other biased plasma-assisted physical vapour deposited transition-metal-based ceramic coatings alloyed with Si (e.g. Ti–Si–N, Cr–Si–N, Cr–Al–Si–N).     

Mechanical and tribological properties of the High Target Utilization Sputtering W-C coatings on different substrates

The effects of three types of substrates (Si, bearing steel, and WC-Co) and acetylene addition (0–3.2 vol.% in Ar atmosphere) on the topography, structure, composition, nanohardness and tribological behavior of the High Target Utilization Sputtering W-C coatings were investigated. The results showed that the substrates affected mostly the coating topography, roughness and nanohardness whereas the composition, indentation moduli and coefficients of friction were influenced only by the increase of free carbon content from acetylene addition. Up to ~ 5 GPa difference in the hardness of the W-C coatings on Si substrates compared to that on steel was obtained. Simultaneously, methodological problems with the hardness measurements were identified on WC-Co substrate which has the hardness close to that of the coatings. The average values of the coefficient of friction were around 0.3 and slightly decreased at higher carbon contents but the influence of the substrates was small.     

(Ti,Cr,Nb)CN coatings deposited on nitrided high-speed steel by cathodic arc method

The combined processes of plasma nitriding and cathodic arc deposition of (Ti,Cr,Nb)CN coatings were applied to HSS substrates. The nitrided layers, obtained in a mixture of H₂ (70%) and N₂ (30%) at two different temperatures (480 °C and 510 °C), were examined for the microhardness depth profiles. Characterization of the duplex coatings was performed by investigating elemental and phase composition, texture, hardness, friction and wear. XRD and XPS analyses revealed the formation of a mixture of a carbonitride fcc solid solution, in a dominant proportion, and metallic chromium. The film hardness was measured to be ~ 34 GPa. The duplex (Ti,Cr,Nb)CN coatings exhibited superior tribological behavior as compared to both nitrided layers and non-duplex coatings.     

The effect of substrate position on the microstructure and mechanical properties of SiC coatings on carbon/carbon composites

In this work, silicon carbide (SiC) coatings were produced on carbon/carbon composites using a chemical vapour deposition (CVD) method. During deposition, the temperature was fixed at 1200 °C and the coatings were produced by placing substrates at three different positions (340, 380 and 420 mm from the inlet) in the CVD reactor. The effect of substrate position on the microstructure and mechanical properties of the SiC coatings were experimentally investigated. The phase composition, surface morphology, defects and microstructure were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman Spectroscopy. The hardness and Young's modulus were measured using a nano-indentation method while fracture toughness was evaluated by micro-indentation. It was found that the deposition rate decreased linearly as substrate position moved far from the reactor inlet. In all coatings, only β-SiC phase was observed with a high density of stacking faults. It was found that the substrate position in the CVD reactor has a significant effect on the microstructure, grain size and crystallinity of the coating. At 340 and 420 mm substrate positions, a well-developed faceted microstructure with high crystallinity was observed while at 380 mm substrate position, the coating having lenticular-like fine grains with low crystallinity was obtained. The hardness values obtained from the top surface of the coatings are found to be higher than those from the cross-section, although the Young's modulus data (measured from the top surface and cross-section) were observed to be similar. At 380 mm substrate position, hardness, Young's modulus and fracture toughness were found to be the lowest compared to that of the coatings produced at 340 and 420 mm substrate positions. It is concluded that the SiC coatings with better mechanical properties can be produced by adjusting the substrate position in the CVD reactor.     

Carbon-based coatings doped by copper: Tribological and mechanical behavior in olive oil lubrication

We deposited C-based films doped with Cu and tested their sliding properties in olive oil as environment-friendly lubricant, which can be used in many mechanical systems, particularly in agriculture engineering. The coatings were deposited in a four unbalanced magnetron sputtering device combining C and C/Cu targets; argon (hydrogen-free films) and Ar/CH₄ (hydrogenated films) atmospheres were used. Cu content of the films was in the range 5–14 at.%. The hardness of the films was almost constant whatever the Cu content was. On the other hand, hydrogen-free coatings were much harder (about 15 GPa) than hydrogenated ones (about 4 GPa). The coatings were oleophilic and their sliding properties were evaluated using ball-on-plate tests with 200,000 cycles. The non-hydrogenated coating with 6 at.% of copper showed the best tribological performance with negligible wear for all olive oil testing temperatures (i.e. up to 120 °C).     

TiAlN,TiAlSiN涂层的制备及其切削性能

目的研究TiAlN及TiAlSiN涂层的微观结构及力学性能,以及硬质合金涂层刀具切削SUS304不锈钢的切削性能及磨损行为。方法采用阴极电弧离子镀技术在硬质合金试片及铣刀上分别制备纳微米TiAlN及TiAlSiN涂层。通过X射线荧光测量系统测量涂层的厚度,用扫描电镜(SEM)观察涂层表面形貌,用能谱仪(EDAX)分析涂层元素成分,用X射线衍射(XRD)分析涂层晶相结构,用纳米压痕仪表征涂层硬度,用洛氏硬度计定性测量涂层结合力,通过高速铣削试验探究涂层刀具的切削性能及磨损行为。结果 TiAlN及TiAlSiN涂层的厚度分别为3.32μm和3.35μm,表面致密、光滑,高分辨率(20 000×)下观察到涂层表面有液滴、针孔及凹坑存在。Si元素促进了Ti N(200)晶相的生长,晶粒尺寸减小,硬度增加。TiAlN及TiAlSiN涂层的显微硬度分别为29.6 GPa及37.7 GPa,结合力分别满足VDI-3198工业标准的HF3和HF1等级。在130 m/min的高速切削条件下,TiAlSiN涂层刀具寿命约为未涂层刀具的5倍,TiAlN涂层刀具的1.5倍。结论 Si掺杂制备的TiAlSiN涂层具有高的硬度及良好的抗粘附性,更适用于不锈钢材料的高速切削加工。     

Structural,mechanical and electrical-contact properties of nanocrystalline-NbC/amorphous-C coatings deposited by magnetron sputtering

Niobium-carbide nanocomposite coatings with a carbon content varying from 43 to 64 at.% were deposited by dual DC magnetron sputtering. X-ray diffraction, x-ray photoelectron spectroscopy and electron microscopy showed that all coatings consisted of nanometer sized NbC grains embedded in a matrix of amorphous carbon. Mechanical properties and electrical resistivity showed a strong dependency on the amount of amorphous carbon (a-C) and NbC grain size in the coating. The highest hardness (23 GPa), elastic modulus (295 GPa) and the lowest resistivity (260 μΩ cm) were measured for the coating with about 15% of a-C phase. Contact resistance measurements using a crossed cylinder set-up showed lowest contact resistance for the coating containing 33% a-C (140 μΩ at a contact force of 100 N), which is comparable to a Ag reference (45 μΩ at a contact force of 100 N). Comparison with TiC-based nanocomposites studied under similar conditions showed that the NbC system has less tendency to form a-C and that lowest contact resistance is obtained at comparable amounts of a-C phase in both material systems (33% for NbC compared to 35% for TiC). With these good electrical contact properties, the NbC nanocomposites can be considered as a potential material for electrical contact applications.     

Thermal and thermo-mechanical properties of Ti–Al–N and Cr–Al–N coatings

Metastable Ti–Al–N and Cr–Al–N coatings have been proven to be an effective wear protection due to their outstanding mechanical and thermal properties. Here, a comparative investigation of mechanical and thermal properties, for Ti–Al–N and Cr–Al–N coatings deposited by cathodic arc evaporation with the compositions (c-Ti_0.52Al_0.48N, c/w-Ti_0.34Al_0.66N and c-Cr_0.32Al_0.68N) widely used in industry, has been performed in detail. The hardness of Ti_0.52Al_0.48N and Ti_0.34Al_0.66N coatings during thermal annealing, after initially increasing to the maximum value of ~ 34.1 and 38.7 GPa with T_a up to 900 °C due to the precipitation of cubic Al-rich and Ti-rich domains, decreases with further elevated T_a, as the formation of w-AlN and coarsening of precipitated phases. A transformation to Cr₂N and finally Cr via N-loss in addition to w-AlN formation during annealing of the Cr_0.32Al_0.68N coating occurs, and thus results in a continuous decrease in hardness. Among our coatings, the mixed cubic-wurtzite Ti_0.34Al_0.66N coating exhibits the highest thermal hardness, but the worst oxidation resistance. The Cr_0.32Al_0.68N coating shows the best oxidation resistance due to the formation of dense protective α-Al₂O₃-rich and Cr₂O₃-rich layers, with only ~ 1.4 μm oxide scale thickness, after thermal exposure for 10 h at 1050 °C in ambient air, whereas Ti–Al–N coatings are already completely oxidized at 950 °C.     

Effect of remelting process on characterization of air-plasma sprayed Fe67.5Ni23.5B9 alloy coatings onto 1Cr18Ni9Ti stainless steel

To develop a composite material with good mechanical and radiation shielding properties, the Fe–Ni–B (Fe_67.5Ni_23.5B₉, wt. %) coatings onto ₁Cr₁₈Ni₉Ti stainless steel substrate (SS, same as below) were prepared using air-plasma spraying (APS) technique in this work. A remelting process (1050 °C/2 h) was performed on the Fe–Ni–B coatings laminated composite under vacuum condition. The microstructure, phase composing, adhesion strength, Vickers hardness distribution and residual stress of Fe–Ni–B coatings before and after the remelting process were contrastively characterized. The results show that the remelting process decrease the coating defects and make the coating more cohesive and stable. The element diffusion and new compounds formation within the coating and interface area improves the adhesion and thermal fatigue of Fe–Ni–B coatings. In addition, the drop of variability of Vickers hardness data and residual stress level qualitatively identify that the Fe–Ni–B coatings possess more consistent microstructure and mechanical integrity after the remelting process.     

Effects of Ti addition on microstructure homogenization and wear resistance of wide-band laser clad Ni60/WC composite coatings

Ni60/WC composite coatings were fabricated by wide-band laser cladding. The effects of Ti addition on microstructure homogenization and coating properties were investigated. Coating microstructure, phase constitution, microhardness and wear resistance were studied and grading analysis of in-situ synthesized ceramic particles was carried out. Results indicated that ceramics particles of Cr₅B₃ and M₂₃C₆ (M represents for Cr and W) carbides were in-situ synthesized in original Ni60-20WC coatings. With Ti addition, dissolution of original WC was facilitated and lots of TiC particles were synthesized instead of M₂₃C₆ carbides. Furthermore, the block Cr₅B₃ particles were greatly homogenized due to the net structure formed by dispersive TiC particles. With Ti addition, D50 of particle size decreased from 8.94 μm to 4.45 μm and particle morphologies were transformed from star-like shapes to uniform square blocks. Microhardness distribution became more uniform with average value decreased from 799 ± 89 HV_0.2 to 744 ± 77 HV_0.2. Due to the homogenized ceramic particles, wear resistance of coatings with Ti addition was enhanced to 2.6 times that of the original coatings.     

Dependence of Microstructure and Hardness of Nanocomposite Coatings of nc-(Ti_(1-x)Al_xN)/a-Si_3N_4 on Aluminum Contents

HARD COATINGS are finding a widely applicationin machining industries as tools and moulds since1980s[1].Hard coatings consisting of a variety of thetransition metal nitrides,for instance,TiN,TiC,TiCN,TiBN,TiAlN,CrN etc,usually service as a protectioncoatings that requires some better properties ofwear-resistance,corrosion-resistance and also highfatigue-strength especially at elevated temperature(formore details see Ref.2-6).The generic concept for the design of novelsuper-hard(>40G…     

Corrosion resistance of Ti–6Al–4V alloy with nitride coatings in Ringer’s solution

The corrosion behaviour of Ti–6Al–4V alloy with nitride coatings was investigated in Ringer’s solution at 36 and 40 °С. Nitride coatings of different composition, thickness and surface quality were formed because of changing nitrogen partial pressure from 1 to 10⁵ Ра and nitriding temperature from 850 to 900 °С. Results shown that nitride coatings improve anticorrosion properties of alloy at both solution temperatures. Corrosion resistance of alloy increases with the content increase of TiN phase in nitride coating. With increase of temperature from 36 to 40 °С the corrosion resistance of alloy is determined significantly by quality of nitride coating.