Mechanical properties and adhesion of TiN monolayer and TiN/TiAlN nanolayer coatings

In this work, TiN monolayer and TiN/TiAlN nanolayer coatings were deposited on 100C6 (AISI 52100) steel substrate by Physical vapor deposited (PVD) magnetron sputtering system. The morphological characterization was evaluated using an atomic force microscopy. The mechanical properties were determined by nanoindentation test. The adhesion was investigated by both microindentation and scratch test. The results show that the TiN/TiAlN nanolayer coating have the more rough surface and the better mechanical properties and adhesion compared to TiN monolayer coating. The effect of microstructural and mechanical proprieties on the adhesion behavior was further discussed. It was found that the improvement in adhesion of nanolayer system is in part due to the increase in plastic deformation resistance and the enhancement of mechanical properties (hardness and elastic modulus) and to the structure with a small grain size and a high number of interfaces.     

Interfacial processing and adhesion of diamond,diamond-like,and TiN films on metallic and polymeric substrates

Diamond, diamond-like, and titanium nitride (TiN) films have extremely desirable chemical, electrical, and mechanical properties for a variety of applications ranging from corrosion- and erosion-resistant coatings to electronics packaging of microelectronic devices. However, many of these applications are limited by the poor adhesion of these films to metal and polymer substrates. The adhesion of a film is determined primarily by internal stresses in the film, thermal and lattice mismatch, and most importantly by interfacial bonding. We have developed methods based on mechanical interlocking, chemical bonding, grading of interatomic potentials, and the multilayer discontinuous thin films approach to control stresses and strains in thin films. A substantial improvement in adhesion and wear properties is obtained by using these methods selectively. We review issues related to the adhesion of diamond, diamond-like carbon, and TiN films on metal and polymeric substrates.     

Analysis of the mechanical properties of TiN/Ti multilayer coatings using indentation under a broad load range

In this study, physical vapor deposition was used to prepare TiN/Ti multilayer coatings as well as the corresponding monolithic coatings for comparison. Nanoindentation using a large load range (5–4800 mN) and finite element method (FEM) simulations were conducted to investigate the influence of various multilayer structures on the mechanical behavior of multilayer coatings. The nanoindentation results show that the TiN/Ti multilayer coating has the maximum hardness and Young's modulus while retaining good crack resistance and fracture toughness. The FEM results show that increasing the number of layers in the multilayer coatings reduced the hardness and Young's modulus as well as the maximum stress, while it increased the equivalent plastic strain. As the layer thickness ratio increased, both the hardness and Young's modulus gradually increased, and the stress in the coating reached its maximum at the highest thickness ratio. In addition, to consider the effect of the indentation depth on the coating, the influence of the number of layers and the layer thickness ratio on the multilayer coating is combined into the indentation response of the multilayer coating. Therefore, we establish an expression describing the relationship between the number of layers and the ratio of the layer thickness to the mechanical properties of TiN/Ti multilayer coatings.     

The effect of nitrogen flow rate on TiBN coatings deposited on cold work tool steel

TiBN coatings have high hardness and high adhesion. Due to these excellent properties there has been increasing interest in TiBN coatings. In this study, TiBN coatings were deposited on AISI D2 cold work tool steel and silicon wafers by closed field unbalanced magnetron sputtering (CFUBMS). The structural, mechanical and adhesion properties of these coatings were analysed by X-ray diffraction, scanning electron microscopy, microhardness test, indentation test and scratch tests. TiBN coatings produced by magnetron sputtering exhibited a dense and columnar structure. These results indicate that TiB₂, TiN and h-BN exist in crystalline forms at all coatings. The highest hardness was obtained at the lowest nitrogen flow rate. Very few cracks were observed at the edge of the indentation marks at the highest nitrogen flow rate. The highest critical load obtained with scratch test was identified as 102?N.     

Effect of transition layer on the performance of hydroxyapatite/titanium nitride coating developed on Ti-6Al-4V alloy by magnetron sputtering

A gradient transition multilayer hydroxyapatite/titanium nitride (HA/TiN) coating was prepared on the Ti-6Al-4V alloy by magnetron sputtering. The composition, surface topography, microstructure, adhesion strength and electrochemical properties of the as-deposited coatings were characterized by SEM/EDS, AFM, XRD, FT-IR and electrochemical workstation. The experimental results showed that the single TiN coating deposited at a partial pressure of nitrogen (N₂) of 0.08?Pa had the best internal stress and tribological performance, and its volume loss was only 0.89% of that of Ti-6Al-4V alloy. The introduction of the TiN transition layer greatly improved the wear resistance of the Ti-6Al-4V alloy, and the adhesion strength of the HA layer to the substrate increased from 6.50?±?0.5?N to 11.70?±?1.2?N, an increase of 56%. The HA/TiN coating surface consisted of uniform hemispherical particles with dense structure and invisible defects (micro-cracks and pores). For the HA surface layer, the crystal structure and active hydroxyl (-OH) group was restored after heat treatment. Potentiodynamic polarization experiments indicated that the HA/TiN coating achieved the lowest corrosion current density and the most positive corrosion potential compared to the single TiN layer and Ti-6Al-4V alloy. In summary, it can be conclude that the gradient transition layer can well improve the mechanical properties and electrochemical behavior of the titanium alloy, and largely ensuring the stability of the surface bioactive coating.     

Characterization of TiCN and TiCN/ZrN coatings for cutting tool application

Coating a cutting tool improves wear resistance and prolongs tool life. Coating performance strongly depends on the mechanical and chemical properties of the coating material. In a machining process, the type of selected coating depends on the cutting condition because of the properties of the applied coating material. In addition, many factors, such as coating thickness, composition ratio, sequences of layers in multilayer coatings, and the deposition method influence the performance of a coating. In this study, the mechanical properties of TiCN and TiCN/ZrN were investigated using a ball on disk test. The substrate material made from a carbide-based cutting tool was also developed in-house. The analysis performed shows that the performances of TiCN and TiCN/ZrN coatings were found to be comparable to that of the commercial TiN-coated carbide-based cutting tool. Both the in-house and commercial coated inserts had significantly lower coefficient of friction than uncoated inserts, and the friction coefficient of TiCN coatings was constantly slightly lower than that of TiN coatings. Moreover, the coefficient of friction of the in-house developed TiCN was slightly lower than that of commercial TiN coating. However, the coefficient of friction of the in-house developed uncoated carbide inserts was slightly higher than that of commercial uncoated carbide inserts.     

On the evaluation of adhesion of coatings by automatic scratch testing

Automatic scratch testing is an expedient technique for comparatively evaluating the cohesive failure load and adhesion failure load of thin coatings on various substrates. In combination with SEM examination of the scratch track, this technique has been used herein to detect and evaluate various effects on coating strength and adhesion. For soft Triballoy T-800 and Stellite SF-6 cobalt-base coatings on 4340 low alloy steel, adhesion was found to be strong and failure was found to be cohesive in the coating. In the presence of a plated chromium interlayer, pre-existing cracks lowered substantially the cohesive failure load, which was also lowered by an increase in the coating deposition pressure. The spacing of transverse cracks within the coating was found in all cases to decrease with increasing applied normal load. In soft aluminum coatings on depleted uranium (DU)-0.75% Ti alloy specimens, alloying aluminum with magnesium or zinc enhanced the coating strength and adhesion. In (Al-Mg) coatings on this substrate, a smoother surface led to a lower friction coefficient and a higher adhesion failure load. In hard, thin TiN coatings on 17-4 PH steel, a lower bias voltage applied to the substrate yielded higher cohesive and adhesion failure loads. In hydrogenated amorphous SiC thin coatings on 4340 steel, loss of hydrogen by annealing converted the residual compressive stresses into tensile stresses and lowered both the cohesive and the adhesion failure loads. Finally, automatic scratch testing proved helpful in determining delamination loads in multilayer TiN/Ti/TiN coatings on DU-0.75% Ti alloy.     

Ag靶弧流对TiN/Ag多层膜结构和性能的影响

采用电弧离子镀技术,通过改变Ag电弧靶的弧流在医用不锈钢基底表面制备TiN/Ag多层膜,分析多层膜的微观结构,测试多层膜的厚度、结合强度和硬度,通过摩擦磨损实验测定多层膜的摩擦系数,研究了不同Ag靶弧流对多层膜结构和性能的影响规律。实验结果表明,在不同Ag靶弧流下,TiN/Ag多层膜有TiN(111)晶面和Ag(111)晶面择优生长。Ag靶弧流在一定程度上影响着多层膜中Ag的结晶度,当弧流为50 A时,Ag的结晶度达到最佳,此时多层膜的结合力最大,为45.33 N;多层膜的硬度达到最小值1 189.4 HV;多层膜的摩擦系数最小,为0.242。Ag靶弧流影响Ag层的结晶度,并且对多层膜的结合强度、硬度和摩擦系数具有明显影响。     

Effects of thickness and substrate on the mechanical properties of hard coatings

Nanoindentation technique was employed to characterize the mechanical properties of TiN coatings deposited on high-speed steel and stainless steel substrates. Effects of thickness and substrate on-the mechanical properties were investigated. The results show that TiN coatings exhibit different mechanical properties corresponding to the variation in thickness and substrate.     

Improvement of anti-erosion performance of TiN coatings through using a filtration cathode vacuum arc deposition method

Sand erosion is a major factor that shortens the service life of aircraft in desert regions. The anti-erosion performance of titanium alloys may be improved using TiN coatings. However, few studies have employed Ti sputtering on Ti transition layers to improve the erosion resistance of the coatings. Herein, TiN coatings with a sputtering layer between the Ti transition layer and the TiN layer were deposited on a Ti–6Al–4V alloy by filtered cathodic vacuum arc deposition. For comparison, another group of TiN coatings without a Ti sputtering layer but processed using the same deposition parameters were prepared. The effects of the nanoscale sputtering layer on the microstructure, mechanical properties, and anti-erosion performance of the coatings were investigated using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and nanoindentation. The results show that the introduction of a Ti sputtering layer promoted the growth of TiN grains, leading to the formation of finer and denser TiN columnar grains. The preferred orientation of the coatings with the sputtering layer is (111) plane, whereas that of the coatings without the sputtering layer is (200) plane. The TiN coatings containing a sputtering layer exhibit higher hardness, elastic modulus, and H³/E² ratio, which enhances the anti-erosion performance of the coatings. The coatings with a sputtering layer exhibited better erosion resistance (erosion rate reduced by 75%) than the coatings without a sputtering layer. The underlying mechanism to understand the effect of the sputtering layer on the erosion resistance was discussed based on variations in the microstructure and mechanical properties of the coatings with and without the Ti sputtering layer. Ti sputtering layer was finally proved to be an effective method to improve the erosion resistance of TiN coatings.     

应用于聚丙烯塑料的水性复合涂层的制备及性能研究

为了解决聚丙烯材料上水性涂料附着力较差的技术难题,首先合成一种丙烯酸酯单体改性水性氯化聚丙烯树脂,采用该树脂制备聚丙烯塑料水性底漆,并研制配套的水性面漆和罩光清漆,制备得到成套水性复合涂层体系。使用傅里叶变换红外光谱仪(FT-IR)、动态光散射(DLS)、凝胶渗透色谱(GPC)和差示扫描量热法(DSC)对所制备丙烯酸改性水性氯化聚丙烯树脂进行结构表征。重点考察了水性底漆的附着力、复合涂层的附着力以及复合涂层的耐热水煮性能,结果表明:水性底漆和复合涂层均表现出优异的附着力,涂层耐热水煮性能较好。最后,对水性复合涂层的性能进行测试,结果表明:复合涂层综合性能优异,在汽车内外饰及各类聚丙烯材料领域具有较大的应用前景。     

Properties of TiN–Al2O3–TiCN–TiN,TiAlN, and DLC-coated Ti(C,N)-based cermets and their wear behaviors during dry cutting of 7075 aluminum alloys

In the work, TiAlN for physical vapor deposition (PVD), multilayer TiN-Al₂O₃-TiCN-TiN for chemical vapor deposition (CVD), and diamond-like carbon (DLC) for plasma-enhanced chemical vapor deposition (PECVD) were deposited on the cermet inserts. Characteristics and wear behaviors of the three coated cermets during dry cutting of 7075 aluminum alloys were observed. The results show that TiN-Al₂O₃-TiCN-TiN coatings have highest adhesion strength and hardness. At the cutting speed of 1100 r/min, the depth of 0.2 mm, and the feed rate of 0.1 mm/r, the three coated inserts show the best wear-resistant properties. In this case, TiN/Al₂O₃/TiCN/TiN shows the worst wear-resistant properties (value of the flank wear [VBB] = 0.062 mm), while DLC coatings show the most excellent wear-resistant properties (VBB = 0.046 mm). During the cutting of aluminum alloys, which have high plasticity and low melting point, adhesive wear dominate on the flank of the inserts. The thickest coating of TiN/Al₂O₃/TiCN/TiN results in the bluntest cutting edge, which form the most serious adhesive worn zone. For the TiAlN and DLC coatings, due to a smaller cutting force, the two coatings have much better wear resistance. Further, the self-lubricating properties of DLC show excellent effect on protecting the inserts. Thus, the DLC-coated cermets have the best wear-resistant properties. Further, the TiAlN-coated cermets have the widest wear-affected zone while the DLC coating has the narrowest.     

Tribomechanical and microstructural properties of cathodic arc-deposited ternary nitride coatings

Sintered carbides are promising materials for surfaces that are exposed to extreme wear. Owing to their high service load, ceramic-based thin films are coated on carbides using different techniques. In this study, non-toxic and cobalt-free powder metallurgy-sintered carbide samples were coated with TiN, TiAlN, CrAlN, and TiSiN ceramic-based thin film coatings by cathodic arc physical vapor deposition. The microstructure (phase formation, coating thickness, surface roughness, and topography), mechanical properties (hardness, modulus of elasticity, and plasticity indices), and tribological properties (nanoscratch and wear behavior) of the thin film coatings were investigated. No cracks or defects were detected in these layers. The ceramic-based ternary nitride thin film coatings exhibited better mechanical performance than the TiN coating. The TiN thin film coating had the highest average surface roughness, which deteriorated its tribological performance. The ternary nitride thin film coatings exhibited high toughness, while the TiN thin film coating exhibited brittle behavior under applied loads when subjected to nanoscratch tests. The wear resistance of the ternary nitride coatings increased by nearly 9–17 times as compared to that of the TiN coating and substrate. Among all the samples investigated, the substrate showed the highest coefficient of friction (COF), while the TiSiN coating exhibited the lowest COF. The TiSiN thin film coating showed improved mechanical and tribological properties as compared to other binary and ternary nitride thin film coatings.     

Friction behavior of TiN–MoS2/PTFE composite coatings in dry sliding against SiC

To improve the dry friction behavior of traditional hard coatings, MoS₂/PTFE lubricating coatings were prepared on the PVD TiN-coated cemented carbide using spray method. The influences of MoS₂/PTFE lubricating coatings on the primary characteristics of TiN coatings were investigated. Reciprocating sliding tests were carried out with the TiN–MoS₂/PTFE coated specimen (T-M-P) under dry sliding conditions, and the tribological behaviors were compared to those of the TiN-coated one (T-N). The test results indicated that the adhesion force of coatings with substrate for T-M-P specimen increased, the surface micro-hardness, roughness and friction coefficient significantly decreased. Meanwhile, the surface adhesions and abrasion grooves of T-M-P specimen were reduced, and the main wear forms of T-M-P were abrasion wear and coating delamination. The MoS₂/PTFE lubricating coatings can be considered effective to improve the friction properties of traditional hard coatings.     

Adhesion and fatigue resistance of Ta-doped MoS2 composite coatings deposited with pulsed-DC magnetron sputtering

MoS₂–Ta composite coatings were deposited using the pulsed-DC magnetron sputtering technique. X-ray diffraction (XRD), scanning electron microscopy, energy dispersive spectroscopy, and atomic force microscopy were used to determine the structural properties of the MoS₂–Ta composite coatings. The hardness values and adhesion and fatigue features of the coatings were determined using a microindentation hardness test and a scratch test, respectively. The scratch tests were evaluated using two modes: a standard mode (under a progressive load) and a multimode (sliding-fatigue with a constant sub-critical load within the same scratch track). Failure mechanisms of the scratch tracks were determined by examining the resulting micrographs. The MoS₂–Ta coatings have a dense columnar microstructure. XRD patterns of the coatings revealed MoS₂ (0?0?2), MoS₂ (1?0?0), MoS₂ (1?0?3), and α-Ta (1?1?0) reflections. The thickness, roughness, hardness, and elemental ratio values of the coatings were significantly affected by the target currents. The adhesion of the coatings dramatically increased with an increase in the thickness, hardness, and Ta/Mo ratio and with decreases in the roughness. The MoS₂–Ta composite coatings with a high load-bearing capacity exhibited excellent fatigue resistance.     

Influence of nitrogen gas over microstructural,vibrational and mechanical properties of CVD Titanium nitride (TiN) thin film coating

In this experimental investigation, the influence of different N₂ gas flow rates on different properties (e.g. morphological, mechanical, etc.) of chemical vapor deposited (CVD) Titanium nitride (TiN) coatings has been discussed. The TiN coatings had been grown on Si (100) substrate at elevated temperature (1000 °C) using Titanium dioxide (TiO₂) powder. SEM images reveal a dense uniform microstructure with an irregular surface pattern. The surface roughness of the coatings was found to be increased from 12.42 to 28.56 nm with an increase in flow rate. XRD results indicate a B1 NaCl crystal structure of the film with reduced crystallite size with the increasing N₂ flow rate. Through the corrosion test, it has been observed that due to the variation of N₂ flow rate the corrosion resistance of the films decreases with increasing N₂ flow rate. The mismatch of thermal expansion co-efficient in between Si substrate and TiN thin film reduces with higher N₂ flow rate. The acoustic and optic phonon mode of TiN coatings have been shifted to higher intensities with higher N₂ flow rate. The mechanical properties of the film reveal that the maximum value of hardness (H) and Young's modulus (E) are 30.14 and 471.85 GPa respectively.     

Effect of electroless nickel interlayer on the electrochemical behavior of single layer CrN, TiN, TiAlN coatings and nanolayered TiAlN/CrN multilayer coatings prepared by reactive dc magnetron sputtering

The electrochemical behavior of single layer TiN, CrN, TiAlN and multilayer TiAlN/CrN coatings, deposited on steel substrates using a multi-target reactive direct current (dc) magnetron sputtering process, was studied in 3.5% NaCl solution. The total thickness of the coatings was about 1.5 μm. About 0.5 μm thick chromium interlayer was used to improve adhesion of the coatings. With an aim to improve the corrosion resistance, an additional interlayer of approximately 5 μm thick electroless nickel (EN) was deposited on the substrate. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to study the corrosion behavior of the coatings. Scanning electron microscopy and energy dispersive X-ray analysis were used to characterize the corroded samples. The potentiodynamic polarization tests showed lower corrosion current density and higher polarization resistance (R_p) for the coatings with EN interlayer. For example, the corrosion current density of TiN coated steel was decreased by a factor of 10 by incorporating 5 μm thick EN interlayer. Similarly, multilayer coatings of TiAlN/CrN with EN interlayer showed about 30 times improved corrosion resistance as compared to the multilayers without EN interlayer. The porosity values were calculated from the potentiodynamic polarization data. The Nyquist and the Bode plots obtained from the EIS data were fitted by appropriate equivalent circuits. The pore resistance (R_pore), the charge transfer resistance (R_ct), the coating capacitance (Q_coat) and the double layer capacitance (Q_dl) of the coatings were obtained from the equivalent circuit. Multilayer coatings showed higher R_pore and R_ct values as compared to the single layer coatings. Similarly, the Q_coat and Q_dl values decreased from uncoated substrate to the multilayer coatings, indicating a decrease in the defect density by the addition of EN interlayer. These studies were confirmed by examining the corroded samples under scanning electron microscopy.     

Application of surface treatments on releasing adhesion force during thermoplastic polyurethane injection molding process

With injection molding process, thermoplastic polyurethane is generally used to fabricate shoes, boots, rollers and golf balls, etc. However, serious adhesion causes molded part difficult to be released from tool surface. To alleviate adhesion force during ejection stage, chromium‐nitride (CrN) based and diamond like carbon (DLC) coatings prepared by physical vapor deposition were coated on mold cavity surface. Single layer CrN and modifying CrN coatings were found to be beneficial to alleviate adhesion force whereas multilayer CrN and DLC surface treatments were ineffective during continuous experiments. Further investigation found that single layer CrN and modifying CrN both had excellent water‐repellency properties with low surface energy and exhibited the distinctive conical structure with uniform grain size. Although multilayer CrN coating exhibited similar morphology as that of single layer CrN coating, it showed significant variations in grain size and height. In contrary, although DLC coating adequately showed uniform topography, its larger grain size and wider valley between grains both lead to larger adhesion force due to mechanical anchoring. POLYM. ENG. SCI., 57:299–305, 2017. © 2016 Society of Plastics Engineers     

Repair of spline shaft by laser-cladding coarse TiC reinforced Ni-based coating: Process,microstructure and properties

To repair the surface defects of spline shaft and improve wear resistance, the coarse TiC reinforced Ni-based composite coatings were fabricated on the spline shaft surface by laser cladding with six types of precursors containing Ni45, coarse TiC, and fine TiN powder. The effects of ceramic content and fine TiN addition on the formability, microstructure, and mechanical properties of the coatings were studied comprehensively. In TiC reinforced Ni-based coatings 1–3 without fine TiN addition, the porosity decreased from 20.415 % to 0.571 % with the increase of TiC concentration. The coatings mainly consist of CrB, Cr7C3, Cr23C6, coarse TiC, and γ-Ni. With the addition of fine TiN, the length of the ceramic phases in coatings 1#–3# decreased slightly, while volume fraction and porosity increased. Moreover, the ring-shaped Ti (C, N) phases were also detected at the edges of both undissolved TiC and TiN particles, which improved the bonding force between ceramics and matrix. Besides, these ceramics inhibited the generation of columnar crystals and eliminated the heat-affected zone. The performance test results show that the coating 3# with 30 wt% TiC and 6 wt% TiN exhibits the best wear resistance despite slightly decreased hardness, and its friction coefficient of 0.409 and wear rate of 42.44 × 10⁻⁶ mm³ N⁻¹·m⁻¹ are, respectively, 0.667 and 0.307 times those of the substrate. Based on the additive/subtractive hybrid manufacturing technology, the optimized coatings were ground to obtain the finishing surface, which indicates that the coarse TiC reinforced coating can be employed in repairing the damaged parts.     

反应等离子喷涂TiN-Al3Ti-Al复相陶瓷涂层的研究

采用反应等离子喷涂法制备了TiN-Al3Ti-Al复相陶瓷涂层,并通过XRD、SEM对复相涂层进行了相分析、表面行貌分析。结果表明涂层主要由TiN、Al3Ti、Al等三相组成;涂层的结构为富硬质相和富软质相堆叠在一起的层状组织;显微压痕和断口表明复合涂层的韧性较Al2O3涂层有着明显提高。