Influence of bilayer period and thickness ratio on the mechanical and tribological properties of CrSiN/TiAlN multilayer coatings

Nanostructured CrSiN/TiAlN multilayer coatings were deposited by a bipolar asymmetric reactive pulsed DC magnetron sputtering system. The thickness ratio of CrSiN to TiAlN layers was fixed at 1:1. The bilayer periods of the coatings were controlled to be from 6 to 40 nm. Furthermore, two CrSiN/TiAlN multilayer coatings with the same bilayer period (20 nm) but different CrSiN/TiAlN thickness ratios (2:8 and 8:2) were also deposited to explore the influence of thickness ratio on the mechanical properties of the multilayer coatings. The crystalline structures of the coatings were determined by a glancing angle X-ray diffractometer. The microstructures of thin films were examined by a scanning electron microscopy and a transmission electron microscopy, respectively. A nanoindenter, a micro Vickers hardness tester, and a pin-on-disk wear tester were used to evaluate the hardness, the toughness and the tribological properties of the thin films, respectively. The maximum hardness of the multilayers was obtained when the bilayer period was at 10 nm for the coating with the same thickness ratio of CrSiN to TiAlN layers (1:1). Meanwhile, the thickness ratio of CrSiN to TiAlN layer had great influence on the hardness and the toughness properties of the multilayer coatings. The hardness and the toughness of the CrSiN/TiAlN multilayer coatings increased as the individual TiAlN layer thickness increased.     

Mechanical and tribological properties evaluation of cathodic arc deposited CrN/ZrN multilayer coatings

Five nanostructured CrN/ZrN multilayer coatings were deposited periodically by cathodic arc evaporation. The bilayer periods of the CrN/ZrN multilayer coatings were controlled in the range of 5 to 30 nm. The structures and bilayer period of the multilayer coatings were characterized by an X-ray diffractometer. The microstructures of thin films were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. Nanoindentation, scratch tests, Daimler–Benz Rockwell-C (HRC-DB) adhesion tests, microhardness and pin-on-disk wear tests were used to evaluate the hardness, adhesion, indentation toughness and tribological properties of thin films, respectively. It was found that the hardness and tribological properties were strongly influenced by the bilayer period of the CrN/ZrN multilayer coatings. An optimal combination of mechanical properties and excellent tribological behavior was found for a coating with a critical bilayer period of 30 nm.     

Mechanical and tribological properties of TiN/Ti multilayer coating

A large area filtered arc deposition (LAFAD) technique was used to deposit TiN/Ti multilayer coatings with fixed TiN layer thickness and different Ti layer thickness. Nanoindention and pin-on-disk tribometer were used to characterize the hardness, elastic modulus, plasticity, friction coefficient, and wear rate of the multilayer coatings. The dependence of the mechanical and tribological properties of the coating on the Ti interlayer thickness was systematically studied. It was found that the increase in the Ti layer thickness resulted in a decrease in the effective hardness and elastic modulus, and an increase in the wear rate, plasticity, and toughness. The coatings with a Ti layer thicknesses of 0, 25 nm and 50 nm possess an excellent combination of high effective hardness (> 20 GPa), high plasticity (> 69%), low friction coefficient, and high wear resistance.     

Improvement of the tribological behaviour of PVD nanostratified TiN/CrN coatings — An explanation

A hard TiN/CrN multilayered coating, consisting of alternating nanometer scale TiN and CrN layers (bilayer period of 40 nm), was deposited by arc evaporation process on M2 tool steel. Monolayered TiN and CrN are also deposited in the same conditions, and used as references. In order to get a better understanding of the tribological behaviour of coated parts, two types of experiments were performed. The dry-sliding wear resistance was evaluated with a ball-on-disk tribometer, while surface fatigue resistance was determined by a cyclic multi-impact test. The architecture of layers is measured by XRD and observed by TEM. The residual stress field was characterised using XRD and the sin²ψ method at a synchrotron radiation facility.All coatings present a columnar microstructure. TiN demonstrated better wear resistance than CrN and this characteristic is still increased two times by using the nanostratified coating. In the same way, the results of surface oligo-cyclic fatigue test confirm the high performance of the nanostructured coating with respect to the monolayered ones. The differences in mechanical properties of coatings evaluated through nanoindentation measurements do not lead to a direct correlation with the tribological results, and therefore cannot explain such differences. Moreover, a microscopic analysis of the samples after both tribological tests reveals two opposite cracking mechanisms. Monolayered TiN and CrN are subjected to a transversal crack propagation until the peeling of the coating, whereas the multilayered coating only undergoes cohesive cracks deviated in the TiN/CrN interface zones. Both opposite behaviours are the consequence of the distribution of stresses along the thickness of the film.     

Wear of PVD Ti/TiN multilayer coatings

The wear characteristics of PVD Ti/TiN multilayer coatings subjected to two-body abrasion and particle erosion have been studied using diamond slurry and silicon carbide particles as abrasive medium and erodant, respectively. The abrasive wear rate of the Ti/TiN multilayer coatings was found to increase with the relative amount of metallic Ti in the coatings. In erosion, the lowest wear rate was recorded for the homogeneous TiN coating. For the Ti/TiN multilayer coatings the erosion rate was found to decrease with an increasing relative amount of metallic Ti in the coatings. It is concluded that the concept of multilayered coatings offers a potent means to tailor the properties of tribological coatings. In particular, demands of different applications can be met by adjusting the relative thickness of metallic Ti in Ti/TiN coatings. The amount of metallic Ti can, for example, be used to control the coating residual stress state. Multilayered Ti/TiN coatings seem promising for combined wear and corrosion protection.     

Microstructures and mechanical properties evaluation of TiAlN/CrSiN multilayered thin films with different bilayer periods

The Ti_0.45Al_0.55N/Cr_0.75Si_0.25N nanoscale multilayered coatings were deposited periodically by a bipolar asymmetric pulsed DC reactive magnetron sputtering technique. The structures and bilayer period of multilayer coatings were characterized by an X-ray diffractometer. The surface and cross-sectional morphologies of thin films were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. The surface roughness of thin films was explored by atomic force microscopy (AFM). A nanoindenter, a micro Vickers hardness tester and pin-on-disk wear tests were used to evaluate the hardness, fracture toughness and tribological properties of the thin films, respectively. Six coatings with bilayer period ranges from 6 nm to 40 nm were produced in this work. It was observed that the hardness increased with increasing bilayer period and reached the maximum at 12 nm and then leveled off at periods larger than 12 nm. An optimal hardness, and plastic deformation resistance, as well as adequate tribological behaviors were found on the coating with a critical bilayer period of 12 nm.     

Hard CrCN/CrN multilayer coatings for tribological applications

Hard coatings were deposited using a cathodic arc evaporation method. The results of investigations of multilayer CrCN/CrN coatings are presented in this article. The microstructure and crystallinity of films have been investigated using X-ray diffraction (XRD). The composition was determined with energy dispersive spectroscopy (EDS). The adhesion of films was estimated on the basis of an analysis of scratch-test results. The hardness and tribological properties of films deposited on hardened and tempered HSS substrates were also investigated. The tribological tests were carried out in a pin-on-disc geometry. The influence of a normal load, sliding speed and a counterpart material on the friction coefficient and the specific wear rate of the coatings were studied. The counterparts were made of HSS and four types of wood: oak, beech, spruce and pine. The hardness and adhesion of multilayer CrCN/CrN coatings are respectively 25 GPa and 120 N.     

Comparison in mechanical and tribological properties of Cr-W-N and Cr-Mo-N multilayer films deposited by DC reactive magnetron sputtering

Cr-W-N and Cr-Mo-N films were deposited on high speed steel substrate by unbalanced DC reactive magnetron sputtering. Cross-sectional scanning electron microscopy (SEM) morphologies of the films confirmed that the bilayer thickness of multilayer became thinner, and then structural transformation occurred from multilayer to composite with increasing the rotation velocity of substrate holder. X-ray diffraction (XRD) patterns indicated that the Cr-W-N films were composed of CrN and W₂N crystalline phases, and the Cr-Mo-N films consisted of crystalline CrN and amorphous/nanocrystalline Mo₂N. Mechanical and tribological properties were investigated by using a nanoindentor and a ball-on-disk tribometer, respectively. The Cr-W-N films exhibited excellent mechanical properties and wear resistance, while Cr-Mo-N films showed lower friction coefficient. Optimal mechanical and tribological properties were obtained in the Cr-W-N multilayer film with a bilayer period of 12 nm.     

Mechanical Properties of Steel Surfaces Coated with HfN/VN Superlattices

Mechanical and tribological evolution on 4140 steel surfaces coated with hafnium nitride/vanadium nitride [HfN/VN] _n multilayer systems deposited in various bilayer periods (Λ) via magnetron sputtering has been exhaustively studied in this work. The coatings were characterized in terms of structural, chemical, morphological, mechanical, and tribological properties by x-ray diffraction (XRD), x-ray photo electron spectroscopy (XPS), atomic force microscopy, scanning and transmission electron microscopy, nanoindentation, pin-on-disk, and scratch tests. Moreover, the failure mode mechanisms were observed via scanning electron microscopy. The XRD results showed preferential growth in the face-centered cubic (111) crystal structure for [HfN/VN] _n multilayered coatings. The best enhancement of the mechanical behavior was obtained when the bilayer period (Λ) 15 nm (n = 80), yielding the highest hardness (37 GPa), and elastic modulus (351 GPa). The values for the hardness and elastic modulus were 1.48 and 1.32 times greater than the coating with n = 1, respectively, as well the lowest friction coefficient (~0.15) and the highest critical load (72 N). These results indicated significant enhancements in mechanical, tribological, and adhesion properties, compared to HfN/VN multilayered systems with bilayer period (Λ) of 1200 nm (n = 1). This hardness and toughness enhancement in the multilayered coatings could be attributed to the different mechanisms that produce the layer formation with nanometric thickness due to the number of interfaces acting as obstacles for crack deflection and dissipation of crack energy. Due to the emergent characteristics of the synthesized multilayered, the developed adaptive coating could be considered as higher ordered tool machining systems, capable of sustaining extreme operating conditions for industrial applications.     

Effect of a multilayer structure and lubrication on the tribological properties of coatings of Fe-W alloys

The methods for expanding the use of nanocrystalline electrolytic Fe-W alloys by creating a multilayer structure and using oil lubrication were studied. It was shown that lubricants can reduce the coefficient of friction and oxygen penetration into the sliding pairs, thus enhancing the wear resistance behaviour of Fe- W coatings as compared to that at dry friction, when the surface tribo-oxidation dominates. The electrodeposition of multilayer Fe-W/Cu coatings from a single bath was shown to be feasible. The tribological and mechanical properties of such coatings were investigated. The multilayer structure was found to improve the wear resistance characteristics of the coatings even at dry friction and at a relatively high normal load of 10 N.     

TEM analysis and tribological properties of Plasma Electrolytic Oxidation (PEO) coatings on a magnesium engine AJ62 alloy

In order to reduce the fuel consumption and pollution, automotive companies are developing magnesium-intensive components. However, due to the low wear resistance of the magnesium (Mg) alloys, Mg cylinder bores are vulnerable to the sliding wear attack. In this paper, a Plasma Electrolytic Oxidation (PEO) process was used to produce oxide coatings on a Mg alloy AJ62 (MgAl6Mn0.34Sr2), developed for Mg engine block, to battle against the wear attack. The surface morphology, coating thickness and tribological properties were tailored by adjusting the PEO process parameters. TEM analysis demonstrated that the PEO coatings had a nanocrystalline structure in the inner dense layer next to the substrate. The PEO coatings exhibited a much better wear resistance and a smaller friction coefficient than the uncoated AJ62 substrate. The tribological performance of the PEO-coated Mg alloy was even better than that of a hypereutectic Al-Si alloy currently used for engine applications under a high contact load.     

New Approach to Ceramic/Metal-Polymer Multilayered Coatings for High Performance Dry Sliding Applications

The combination of thermally sprayed hard coatings with a polymer based top coat leads to multilayered coating systems with tailored functionalities concerning wear resistance, friction, adhesion, wettability or specific electrical properties. The basic concept is to combine the mechanical properties of the hard base coating with the tribological or chemical abilities of the polymer top coat suitable for the respective application. This paper gives an overview of different types of recently developed multilayer coatings and their application in power transmission under dry sliding conditions. State of the art coatings for dry sliding applications in power transmission are mostly based on thin film coatings like diamond-like carbon or solid lubricants, e.g. MoS₂. A new approach is the combination of thin film coatings with combined multilayer coatings. To evaluate the capability of these tribological systems, a multi-stage investigation has been carried out. In the first stage the performance of the sliding lacquers and surface topography of the steel substrate has been evaluated. In the following stage thermally sprayed hard coatings were tested in combination with different sliding lacquers. Wear resistance and friction coefficients of combined coatings were determined using a twin disc test-bed.     

Effect of number of layers on erosion,corrosion, and wear resistance of multilayer Cr–N/Cr–Al–N coatings on AISI 630 stainless steel

In the present study, multilayered Cr–N/Cr–Al–N coatings were prepared by cathodic arc physical vapor deposition (PVD) with different numbers of layers and the same total thickness on AISI 630 steel in an attempt to improve the wear and erosion–corrosion resistance. Structural analysis of the coatings was performed by field scanning electron microscopy, X-ray diffraction (XRD), and energy-dispersive spectroscopy. Depth profiles and roughness parameters of worn surfaces were calculated after erosion and wear tests. XRD indicated that nitride compounds were formed in multilayer coatings by PVD. The Cr–N/Cr–Al–N coating exhibited superior corrosion resistance compared with AISI 630 substrate. The erosion–corrosion results revealed that the smoothest wear track with the minimum erosion rate and wear depth was obtained for five- and seven-layered coatings. The failure mechanism of the bare substrate was influenced by plastic deformation via cutting and plowing, while the failure mechanism for coated samples was chipping and delamination. According to the wear results, the multilayer coatings showed a lower friction coefficient and better surface morphology that demonstrated their high ability for wear protection.     

The tribological behaviour of detonation sprayed TiMo(CN) based cermet coatings

The objective of the present study was to evaluate the tribological performance of 200 μm thick TiMo(CN)–28Co and TiMo(CN)–36NiCo coatings obtained using the detonation spray coating system. Towards the above purpose, the detonation spray coating conditions were optimized to obtain the best coating properties (low porosity, high wear resistance) by varying two of the important coating process variables, i.e., oxygen to fuel ratio and gas volume. In both the coatings it was observed that the best tribological performance and also the lowest porosity were obtained at intermediate OF ratios. However, the coatings with the highest hardness did not exhibit the best tribological performance. A comparison of the tribological performance of the optimized TiMo(CN) type coatings with that of optimized WC–Co coatings revealed that the abrasion resistance of TiMo(CN) type coatings is comparable to that of WC–Co coatings. However, the erosion and sliding wear resistance of TiMo(CN) type coatings were considerably lower than that of WC–Co coatings.     

Mechanical and tribological evaluation of PVD WC/C coatings

Five different WC/C coatings deposited by physical vapour deposition (PVD) on high speed-steel (HSS) have been evaluated with respect to their mechanical and tribological properties. For all coatings a chromium layer was deposited first to enhance coating adhesion. The carbide phase (WC) and the carbon (C) phase were deposited simultaneously by direct-current magnetron sputtering of a WC target and plasma-assisted chemical vapour deposition using hydrocarbon gas, respectively. The influence of the chromium interface layer thickness, the amount of WC phase and the flow of hydrocarbon gas on the mechanical and tribological properties of the coatings have been investigated. The coatings have been characterised with respect to their chemical composition (glow discharge optical emission spectroscopy), hardness (Vickers microhardness), morphology (scanning electron microscopy, SEM), roughness (profilometry), residual stress (beam bending), critical load (scratch testing) and abrasive wear resistance (the “dimple grinder test”). Furthermore, a ball-on-plate test was employed to obtain information about the frictional properties and sliding wear resistance of the coatings. The wear mechanisms and wear debris were analysed by SEM, Auger electron spectroscopy and electron spectroscopy for chemical analysis. All WC/C coatings displayed a thickness between 2 and 4 μm and a surface roughness in the range of 10 to 70 nm. The hardness varied between 1500 and 1800 HV. The coating residual stress was found to range from −2.5 to −0.5 GPa. The scratch test revealed a relatively high critical normal load, i.e., a relatively good adhesion of the WC/C coatings to the HSS. The abrasive wear resistance was found to be very high, in fact equally as high as that of PVD TiN. In the sliding wear test it could be seen that the coating containing the lowest amount of carbide phase (WC), i.e., the highest amount of carbon phase (C), and which had the highest compressive residual stress yielded the lowest friction and wear rate against steel. In addition, this coating was also found to yield the lowest wear rate of the counter material. In summary, a WC/C coating with overall good mechanical and tribological properties was obtained provided a relatively thin chromium layer was deposited first and if a relatively high acetylene gas flow was utilised during deposition of the WC/C layer.     

等离子喷涂硫化亚铁润滑层的摩擦学性能

利用等离子喷涂在 45钢表面制备了三种厚度不同的硫化亚铁固体润滑层。在QP 1 0 0摩擦磨损试验机上测定了硫化亚铁喷涂层在油润滑条件下的摩擦学性能。利用XRD分析了硫化亚铁喷涂层的相结构 ,用SEM观察了喷涂层的磨面形貌。结果表明 ,硫化亚铁喷涂层的减摩、耐磨、抗擦伤性能明显优于 45钢原始表面。     

Mechanical and tribological properties of nanocomposite TiSiN coatings

TiSiN coatings with a thickness of 2.5 μm were deposited using a Large Area Filtered Arc Deposition (LAFAD) technique with TiSi targets having different Si content. The influence of the Si content in the coatings on the mechanical properties and tribological behaviors of the TiSiN coatings were systematically studied using nanoindentation and a pin-on-disk tribometer. Nanoindentation results show that the hardness and Young's modulus of the TiSiN coatings increase with increasing Si content in the coatings. Wear test results indicate that the wear rate and friction coefficient of the 440a stainless steel coupons were significantly reduced by deposition of the TiSiN coatings, and the tribological behaviors of the TiSiN coatings are strongly dependent on the Si content in the coatings and the testing ball material. TiSiN coatings exhibit similar friction coefficient when tested against Al₂O₃ and 302 stainless steel balls, but increasing Si content in the coatings causes an increase in the friction coefficient of the TiSiN coatings. With the increase in the Si content in the coatings, the wear rate of the TiSiN coatings decreases when tested against Al₂O₃ balls, but increases significantly when tested against 302 stainless steel balls. The capability of forming a transfer layer on the ball surface contributes to the change in the friction coefficient and wear rate with Si content in the coating and ball materials.     

Fabrication, microstructure and tribological behavior of pulsed laser deposited a-CNx/TiN multilayer films

a-CN_x/TiN multilayer films were deposited onto high-speed steel substrates by pulsed laser ablation of graphite and Ti target alternately in nitrogen gas. The composition, morphology and microstructure of the films were characterized by energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. The tribological properties of the films in humid air were investigated using a ball-on-disk tribometer. The multilayer films consist of crystalline TiN, metallic Ti and amorphous CN_x (a-CN_x). With an increase in thickness ratio of CN_x to bilayer, the hardness of multilayer film decreases, friction coefficient decreases from 0.26 to 0.135, and wear rate increases. The film with thickness ratio of CN_x to bilayer of 0.47 exhibits a maximum hardness of 30 GPa and excellent wear rate of 2.5 × 10^− 7 mm³ N^− 1 m^− 1. The formation of tribo-layer was observed at contact area of Si₃N₄ ball. The film undergoes the combined wear mechanism of abrasion wear and adhesion wear.     

A comparative study of tribological behavior of plasma and D-gun sprayed coatings under different wear modes

In recent years, thermal sprayed protective coatings have gained widespread acceptance for a variety of industrial applications. A vast majority of these applications involve the use of thermal sprayed coatings to combat wear. While plasma spraying is the most versatile variant of all the thermal spray processes, the detonation gun (D-gun) coatings have been a novelty until recently because of their proprietary nature. The present study is aimed at comparing the tribological behavior of coatings deposited using the two above techniques by focusing on some popular coating materials that are widely adopted for wear resistant applications, namely, WC-12% Co, A1₂O₃, and Cr₃C₂-MCr. To enable a comprehensive comparison of the above indicated thermal spray techniques as well as coating materials, the deposited coatings were extensively characterized employing microstructural evaluation, microhardness measurements, and XRD analysis for phase constitution. The behavior of these coatings under different wear modes was also evaluated by determining their tribological performance when subjected to solid particle erosion tests, rubber wheel sand abrasion tests, and pin-on-disk sliding wear tests. The results from the above tests are discussed here. It is evident that the D-gun sprayed coatings consistently exhibit denser microstructures and higher hardness values than their plasma sprayed counterparts. The D-gun coatings are also found to unfailingly exhibit superior tribological performance superior to the corresponding plasma sprayed coatings in all wear tests. Among all the coating materials studied, D-gun sprayed WC-12%Co, in general, yields the best performance under different modes of wear, whereas plasma sprayed Al₂O₃ shows least wear resistance to every wear mode.     

Effect of micro-blasting on the tribological properties of TiN/MT-TiCN/Al2O3/TiCNO coatings deposited by CVD

The effect of micro-blasting on the tribological properties of TiN/MT-TiCN/Al₂O₃/TiCNO coatings was studied. The multilayer coatings were deposited on cemented carbides by chemical vapor deposition. The microstructure, mechanical and tribological properties were investigated using X-ray diffraction, scanning electron microscopy (SEM), nano-mechanical testing system, scratch tester and reciprocating tribometer. The results show that micro-blasting significantly reduces the surface roughness and converts the residual tensile stress of Ti(C,N,O) top-layer and Al₂O₃ layer into compressive stress. Affected by the residual compressive stress, the hardness and adhesion strength are increased. More importantly, the friction coefficient is decreased attributed to the decreased surface roughness and improved hardness. Also, the wear resistance of micro-blasted TiN/MT-TiCN/Al₂O₃/TiCNO is superior due to higher hardness of Ti(C,N,O) top-layer, Al₂O₃ layer and adhesion strength of coatings. Especially for the total sliding time of 2 h, the wear volume and wear rate of micro-blasted coatings are 69.4% of as-deposited coatings, because micro-blasting helps to increase the adhesion strength and micro-cracking resistance, which play important roles in the improvement of wear resistance. Micro-blasting has a positive effect on the friction and wear properties of TiN/MT-TiCN/Al₂O₃/TiCNO multilayer coatings since the adverse impact of top-layer thinning is offset.