Mechanical and tribological properties of TiN and SiCN nanocomposite coatings deposited using methyltrichlorosilane

The paper examines nanocomposite coatings based on TiN and SiCN obtained by plasma-enhanced chemical vapor deposition (PECVD) using methyltrichlorosilane (MTCS) as one of the precursors. The nanocomposite coatings demonstrate four types of structures depending on deposition modes: nc-TiN, nc-TiN/a-SiCN, nc-TiNC/nc-TiSi₂/a-SiCN, and nc-TiNC/nc-TiCl₂/a-SiCN. The nanohardness and elastic modulus of the coatings reach 31 and 350 GPa, respectively. The coatings on substrates of hard alloys, high-speed steel, and silicon increase the nanohardness of the base from 10 to 100%. The correlation between the H/E ratio and wear resistance is not observed. The coatings deposited at low radiofrequency powers demonstrate good adhesion to silicon substrates. It is shown that the use of MTCS as the main precursor allows one to obtain hard and wear-resistant nanocomposite coatings. __________ Translated from Poroshkovaya Metallurgiya, Vol. 47, No. 1–2 (459), pp. 125–133, 2008.     

Wear-resistant Ti-Al-Si-C-N coatings produced by magnetron sputtering of SHS targets

The results of an investigation into hard wear-resistant nanostructured coatings in the Ti-Al-Si-C-N system produced by the magnetron sputtering of multicomponent composite targets with various ratios of metallic and nonmetallic elements are presented. Coatings are deposited in the reaction gas mixture with constant values of the substrate temperature and bias voltage. The structure of coatings is investigated using X-ray diffraction, glow-discharge optical emission spectroscopy, scanning and transmission electron microscopy. The mechanical and tribological properties are determined using the nanoindentation and scratch-testing methods, as well as using tribological tests according to the “pin-on-disc” scheme. The results of investigations show that the coatings are based on the fcc phase consisted of titanium carbonitride with an average crystallite size of 2–20 nm; the crystallites are arranged in an amorphous matrix. The coatings of optimal composition possess hardness of 40–50 GPa, a stable friction coefficient of <0.55, an adhesion strength of ≥50 N, and a wear rate of <1 × 10^?5 mm³/(N m).     

Hard amorphous silicon carbonitride coatings produced by plasma enhanced chemical vapour deposition

Hard amorphous silicon carbonitride coatings for wear resistance have been produced by d.c. plasma‐enhanced chemical vapour deposition on pure iron at 573 K. Compared with most plasma assisted processes work was conducted under a relatively high pressure of 130 Pa. The advantages of this technique are an amorphous film structure, high deposition rates (up to 2 μm/min), high hardness and simple equipment. Hexamethyldisilazan (HMDSN) was used as precursor and argon, hydrogen, nitrogen and ammonia as process gases. The dependence of the coatings on the process parameters (process gas and d.c. power) was investigated. The characterization of the samples was carried out mainly by Fourier transform infrared spectrometry (FTIR), electron probe microanalysis (EPMA) and hardness measurement. Samples show clearly the infrared spectra absorption bands characteristic of SiC and Si₃N₄, with traces of hydrogen bonding. The material structure shows a strong dependence on the process gas and the d.c. power. However, for argon and hydrogen were deposited carbon‐rich SiC films with low nitrogen content. Nitridic films with low carbon content were deposited using nitrogen and especially ammonia. The hardness of the produced coatings was about 10 ‐ 55 GPa.     

A comparative wear study of sputtered ZrN coatings on Si substrate

ZrN coatings were grown on silicon (100) substrate by reactive pulsed direct current sputtering in a mixture of argon and nitrogen gases. The structural parameters and crystallite size as a function of substrate temperatures in the range 300–873 K were studied using x-ray diffraction. A comparative wear Study of ZrN coatings was performed with steel and ceramic balls to evaluate the frictional properties of coatings. It was found that coefficient of friction of ZrN coatings tested with steel ball is lower than the coatings tested with ceramic balls. It is also found that the coefficient of friction is lower for the coatings deposited at higher temperature (873 K) than the coatings deposited at lower temperature (300 K). The morphology and phase distribution of the wear tracks were examined using scanning electron microscope and were correlated with tribological properties     

316L钢表面超音速火焰喷涂Fe基粉末涂层显微结构及摩擦性能分析

经过液氮循环工艺获得了塑韧性更优的Fe基粉末,通过超音速火焰喷涂（high velocity oxy-fuel,HVOF）法对建筑用316L钢基体表面造成高速撞击生成Fe基粉末涂层,分析涂层摩擦学特性与液氮循环工艺间的关系。研究结果表明:液氮循环处理粉末和未处理原始粉末都属于非晶态,粉末外观形貌都属于椭球形,没有开裂或破碎。在液氮循环处理粉末涂层组织中只存在少量的未铺展颗粒,孔隙率也发生了明显减小,形成了更致密组织。采用液氮循环方法来改善粉末塑性,使粉末以更好的铺展状态完成沉积过程。经过液氮循环处理的粉末涂层可以获得更稳定的摩擦学性能,形成了更致密的组织,孔隙与裂纹数量明显降低,摩擦系数明显减小,主要发生氧化磨损,表现出更低的磨痕深度与磨损率误差。     

不同过渡层对CrCN涂层性能的影响

利用多弧离子镀技术,以乙炔和氮气为反应气体,在316 L不锈钢和单晶硅基体上设计3种不同的过渡层（无过渡层,Cr,CrN）制备CrCN涂层,通过X射线衍射仪（XRD）、扫描电镜（SEM）、纳米压痕仪、CSM划痕测试仪和UMT-3多功能摩擦磨损试验机等对3种涂层的微观结构、力学性能和摩擦学性能进行表征.结果表明： CrCN,Cr/CrCN及CrN/CrCN涂层的平均表面粗糙度分别为77.3 nm,74.5 nm及68.1 nm,整体表现出递减的趋势.CrCN,Cr/CrCN及CrN/CrCN涂层的结合力和硬度分别为20.5 N,43 N,61 N及17.4 GPa,21.4 GPa,24.1 GPa.较之于单层CrCN涂层, CrN/CrCN复合涂层的硬度及结合力提高最为显著,并对CrCN涂层起到强有力的支撑作用,从而在大气、去离子水、海水环境下表现出较低的摩擦系数及磨损率.     

Nanostructured Ti-Cr-B-N and Ti-Cr-Si-C-N coatings for hard-alloy cutting tools

Nanostructured Ti-Cr-B-N and Ti-Cr-Si-C-N coatings with various contents of chromium and nitrogen are obtained by the magnetron sputtering of multiphase composite targets. Their structure and phase composition are investigated by X-ray phase analysis, transmission and scanning electron microscopy, X-ray photoelectron spectroscopy, and optical emission glow-discharge spectroscopy. The Ti-Cr-B-N and Ti-Cr-Si-C-N coatings are based on the fcc phase with texture (100) and crystallite size <25 nm. The Si₃N₄-based hexagonal phase was also revealed in the Ti-Cr-Si-C-N coatings. An investigation into the properties of coatings with the use of methods of nanoindentation, scratch testing, and by performing tribological tests showed that they have a hardness of up to 30 GPa, an adhesion strength no lower than 35 N, and their friction coefficient falls in the range of 0.35–0.57. Coatings also possess high thermal stability, resistance to oxidation, and corrosion stability in a 1N H₂SO₄ solution. The data obtained in tests of hard-alloy cutting tools indicate that the deposition of nanostructured Ti-Cr-B-N and Ti-Cr-Si-C-N coatings increases its resistance by a factor of 11–17.     

Properties of nanostructured TiN-Ni ceramic-metal coatings obtained by ion-plasma vacuum-arc method

Physicomechanical and tribological properties of TiN-Ni ceramic-metal coatings prepared by ion-plasma vacuum-arc deposition are investigated. It is established that the hardness (H) increases from 23 to 54 GPa with the Ni content from 0 to 12 at %, which is determined by the influence of the nanostructured nitride component of coatings. Coefficients HE ^?1 and H ³ E ^?2, which characterize the material resistance against the elastic and plastic failure deformation, reach 0.104 and 0.567 GPa, respectively. The further increase in the nickel concentration in coatings to 26 at % leads to a decrease in H to 23–25 GPa, which is associated with the influence of the increasing amount of soft plastic metal and the formation of noticeable porosity in the bulk of coatings. The friction coefficient of studied coatings is 0.45, against 0.58 (for the TiN coating) and 0.72 (for the hard-alloy base). The cohesion failure mechanism of TiN-Ni nanostructured coatings (C _Ni = 2.8–12 at %) is established, and critical loads which characterize the appearance of the first crack (13.5–14.2 N) and the local coating attrition up to the substrate (61.9–64.4 N) are determined. The complete attrition of coatings does not occur up to a load of 90 N, which points to their high adhesion strength. The developed nanostructured ceramic-metal coatings are characterized by high heat resistance up to 800°C.     

316L不锈钢表面沉积CrCN薄膜的结构及性能研究

利用多弧离子镀技术在316L不锈钢和单晶硅上沉积CrCN薄膜,通过X射线衍射仪(XRD)、扫描电镜(SEM)、X射线光电子能谱仪(XPS)、纳米压痕仪、273A电化学工作站和多功能摩擦磨损试验机等对316L不锈钢及CrCN薄膜的微观结构、力学性能、耐腐蚀性能和摩擦学性能进行表征.结果表明:在316L不锈钢上沉积CrCN薄膜后,硬度从4 GPa提高到22 GPa,H/E和H3/E2分别从0.022和0.002 GPa提高到0.071和0.11 GPa;阳极腐蚀电位从-0.21 V上升到-0.19 V;在大气,去离子水,海水环境下的摩擦系数及磨损率均显著降低,表现出较优异的综合性能.     

Wear-resistant amorphous and nanocomposite steel coatings

In this article, amorphous and nanocomposite thermally deposited steel coatings have been formed by using both plasma and high-velocity oxy-fuel (HVOF) spraying techniques. This was accomplished by developing a specialized iron-based composition with a low critical cooling rate (≈10⁴ K/s) for metallic glass formation, processing the alloy by inert gas atomization to form micron-sized amorphous spherical powders, and then spraying the classified powder to form coatings. A primarily amorphous structure was formed in the as-sprayed coatings, independent of coating thickness. After a heat treatment above the crystallization temperature (568 °C), the structure of the coatings self-assembled (i.e., devitrified) into a multiphase nanocomposite microstructure with 75 to 125 nm grains containing a distribution of 20 nm second-phase grain-boundary precipitates. Vickers microhardness testing revealed that the amorphous coatings were very hard (10.2 to 10.7 GPa), with further increases in hardness after devitrification (11.4 to 12.8 GPa). The wear characteristics of the amorphous and nanocomposite coatings were determined using both two-body pin-on-disk and three-body rubber wheel wet-slurry sand tests. The results indicate that the amorphous and nanocomposite steel coatings are candidates for a wide variety of wear-resistant applications.     

Laser Processing of Fe-Based Bulk Amorphous Alloy Coatings on Titanium

Laser Engineered Net Shaping (LENS?), a solid freeform fabrication technique, was employed for the processing of Fe-based bulk amorphous alloy (Fe BAA) powder on titanium. One and two layers of the Fe BAA were deposited with the same processing parameters. SEM and XRD analyses of the Fe BAA coatings revealed the retention of the feedstock powder’s amorphous nature. The mixing of the feedstock powder in the titanium substrate was very small. A crystalline-amorphous composite microstructure evolved from the laser processing in all types of coatings. The coatings were further laser remelted. The amorphous character was found to increase and the crystallites were found to grow during remelting. The Fe BAA coatings showed higher hardness and smaller wear volume compared to the Ti substrate. A further increase in these properties was observed after laser remelting treatment. During the wear testing in NaCl solution, Ti substrate showed intergranular corrosion, whereas the Fe BAA coatings showed signs of low and localized fretting corrosion in a saline environment. Our results demonstrate that using LENS?, amorphous coatings can be deposited on metallic substrates.     

Structure and Tribological Properties of B83 Babbit–Based Composite Rods and the Coatings Produced from Them by Arc Surfacing

Surfacing composite rods based on a B83 babbit alloy reinforced by silicon carbide and boron carbide particles are fabricated by extrusion. The structure and the tribological properties of the rods are studied. Extrusion allowed us to introduce and to uniformly distribute reinforcing fillers and to change the size and the morphology of the intermetallic phases in the matrix alloy. The wear resistance of the rods made of the B83 babbit + 5 wt % SiC composite material is shown to be higher than that of commercial B83 alloy samples by a factor of 1.2. Arc surfacing is used to deposit antifriction coatings, which are made of the surfacing composite rods based on B83 babbit reinforced by boron carbide or silicon carbide particles, onto steel substrates. The deposited layers exhibit good adhesion to the substrates: the melting line is continuous and does not contain discontinuities. The structure and the tribological properties of the deposited coatings are studied. The wear resistance of the composite coatings is higher than that of the B83 alloy–based coating by 30%.     

CrAlN/VN多层膜调制比对涂层性能的影响

为开发适用于干式切削的既硬又润滑的涂层,采用磁控溅射工艺制备调制周期厚度为20nm的CrAlN/VN多层膜结构涂层,研究不同CrAlN/VN调制比对涂层性能的影响;利用场发式电子探针(FE-EPMA)、掠入射X射线衍射分析仪(GIXRD)、场发式扫描电镜(FE-SEM)、透射电子显微镜(TEM)和X射线光电子能谱仪(XPS)表征涂层的微观结构和化学组成;利用纳米压痕仪表征涂层的纳米硬度和弹性模量;利用Ball-on-disc磨耗试验仪表征涂层的摩擦因数。结果表明:当CrAlN/VN的调制比为1∶2时,涂层具有最高硬度(21.8GPa);涂层与碳化钨合金的摩擦因数最低为0.26。随着CrAlN/VN调制比的增大或减小,伴随着CrAlN或VN子层厚度减薄,涂层的硬度有增强的趋势;随着VN含量的增加,涂层的摩擦因数略有下降。     

Wear of Plasma Sprayed Conventional and Nanostructured Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and Cr<Subscript>2</Subscript>O<Subscript>3</Subscript>, Based Coatings

An ever increasing demand for high-performance ceramic coatings has made it inevitable for developing techniques with precise control over the process parameters to enable the fabrication of coatings with the desired microstructure and improved structural properties. The literature on plasma sprayed nanostructured ceramic coatings such as of Al₂O₃, Cr₂O₃, and their composites obtained using reconstituted nano sized ceramic powders has been reviewed in this study. Ceramic coatings due to their enhanced properties are on the verge of replacing conventional ceramic coatings used for various applications like automotive systems, boiler components, power generation equipment, chemical process equipment, aircraft engines, pulp and paper processing equipment, land-based and marine engine components, turbine blades etc. In such cases, the advantage is greater longevity and reliability for realizing the improved performance of ceramic coatings. It has been observed that the plasma sprayed nanostructured ceramic coatings show improvement in resistance to wear, erosion, corrosion, and mechanical properties as compared to their conventional counterparts. This article reviews various aspects concerning the plasma sprayed ceramic coatings such as (i) the present understanding of formation of plasma-spray coatings and factors affecting them, (ii) wear performance of nanostructured Al₂O₃, Cr₂O₃ and their composite ceramic coatings in comparison to their conventional counterparts, and (iii) mechanisms of wear observed for these coatings under various conditions of testing.     

A comparative Study on the Wear Behavior of Al2O3 and SiC Coated Ti-6Al-4V Alloy Developed Using Plasma Spraying Technique

This paper reports the wear characteristics of the ceramic coatings made with Al₂O₃ and also with SiC which were performed using atmospheric plasma spraying technique on the Ti-6Al-4V biomedical alloy with the aim of improving their tribological behavior. The wear behavior of the coatings was evaluated using reciprocatory wear tester with coated substrate as the flat and alumina ball as a friction partner in simulated body fluid (Hank’s solution) environment. The microstructure and phase composition of the ceramic powders and as-sprayed coatings have been characterized using scanning electron microscope and X-ray diffractometer. Porosity, microhardness, adhesion strength and roughness of the coatings were measured as they have a bearing on wear and friction behavior. The results indicate that plasma sprayed Al₂O₃ coating exhibits higher wear resistance compared to that of plasma sprayed SiC coating. The higher wear resistance of Al₂O₃ coating is attributed to the improved melting and spreading of the alumina particles onto the substrate yielding increasingly bonded splats, resulting in compact and dense microstructure with lower porosity and higher microhardness.     

AlCrN/硅系陶瓷在大气、海水环境下的摩擦学性能

采用多弧离子镀技术在316L不锈钢基底上沉积AlCrN涂层.通过扫描电子显微镜（SEM）、X射线衍射仪(XRD)、纳米压痕仪等分析测试手段,对镀层的形貌、成分、相结构、硬度等进行表征,并利用摩擦磨损实验机Rtec考察AlCrN/陶瓷（Si₃N₄、SiC）在大气、海水环境下的摩擦学性能.结果表明:在大气、海水环境下,AlCrN/SiC的摩擦系数和磨损率都远小于AlCrN/Si₃N₄;SiC球表面的微观凹坑对氧化膜SiO₂起到收纳作用,同时减少磨粒磨损.较之于Si₃N₄陶瓷配副,AlCrN涂层与SiC陶瓷对磨时表现出更为优异的摩擦学性能.      

Deposition of Amorphous Hardening Coatings by Electrospark Treatment in a Mixture of Crystalline Granules

This article is devoted to the formation of amorphous coatings on the steel 35 surface by electrospark treatment in a mixture of crystalline granules. It is revealed by the energy dispersive X-ray spectroscopy (EDS) that formed coatings contain W, Mo, Co, and Ni in various ratios. The weight of granules of various compositions decreases by 11–16 wt % for 6-h treatment due to electric erosion. The mass transfer coefficient varies in a range from 33 to 54%. X-ray structural analysis showed the prevalence of an amorphous phase (81–99%) in the structure of deposited layers. Annealing of coatings at a temperature above 1150°C leads to the crystallization of the amorphous phase into boron carbide of the M23(C, B)6 type, as well as into α-Fe. The coatings have an increased hardness of 10–15 GPa, while their wear resistance in the dry sliding wear mode under loads of 10 and 50 N is higher than for steel 35 by a factor of 3.3 and 1.6. The coating friction coefficient is lower than for steel 35 by 13–30% and was 0.27–0.31. The wear resistance of coatings in a dry abrasive wear mode is higher by a factor of 3–5 when compared with uncoated steel 35. The best characteristics are inherent without nickel and worst are inherent without cobalt. Thus, it is established that tungsten and cobalt increase the wear resistance of iron-based amorphous alloys, while nickel and molybdenum tend to worsen their tribotechnical behavior.     

Self-lubricating CrVN Coating Strengthened via Mul-tilayering with VN

To improve the mechanical properties of self-lubricating chromium vanadium nitride （CrVN） coatings, va- nadium nitride （VN） is combined with CrVN to form multilayered CrVN/VN coatings through an in-line magnetron sputtering system. The strengthening effect of the period thickness on the mechanical and tribological properties is studied. X-ray diffractometer, low-angle X-ray reflectivity, scanning electron microscopy, atomic force microscopy, electron probe micro-analyzer and X-ray photoelectron spectroscopy are employed to characterize the microstructures and chemical composition. Nanoindentation and ball-on-disc tribo-tester are used in characterization of the mechanical and tribological properties. The CrVN/VN multilayer coatings demonstrate good lubrication property with coefficient of friction down to 0.23. Multilayering with VN, the hardness of CrVN jumps to 27.6 GPa with period thickness of 6 nm, which has an improvement of 5.1 GPa compared with that of 22.5 GPa from rule-of-mixture.     

Thick Low-Friction nc-MeC/a-C Nanocomposite Coatings on Ti-6Al-4V Alloy: Microstructure and Tribological Properties in Sliding Contact with a Ball

In this paper, we show that duplex surface treatment, combining oxygen diffusion hardening with the subsequent deposition of thick, low-friction nanocomposite nc-MeC/a-C coatings to improve the tribological properties of the Ti-6Al-4V alloy. We have synthesized, in a magnetron sputtering process, the nanocomposite nc-MeC/a-C coatings (where Me denotes W or Ti transition metal) consisting of two dissimilar materials (nanocrystallites of transition metal carbides MeC and an amorphous carbon matrix a-C). The nano and microstructure of the substrate material and coatings were examined with the use of scanning and transmission electron microscopy as well as by X-ray diffractometry. It was found that different carbide nanocrystals of the same transition metal were embedded in an amorphous carbon matrix of both coatings. The HRTEM analysis indicated that the volume fraction of tungsten carbides in the nc-WC/a-C coating was equal to 13 pct, whereas in the nc-TiC/a-C one the volume fraction of the titanium carbides was equal to just 3 pct. The tribological properties, hardness, and scratch resistance of the coatings were investigated as well. The coefficient of friction (COF) of the coatings during dry sliding against 6 mm diameter alumina ball reached very low value, 0.05, in comparison with an oxygen-hardened alloy, whose COF was equal to 0.8. This low-friction effect of the coatings has been attributed to the formation of a self-lubricating film in sliding contact. The coatings exhibited similar failure morphology in the scratch tests. Even though the hardness was rather low, the coatings exhibited a very good wear resistance during sliding friction. The wear rate of the nc-WC/a-C coating was equal to 0.08 × 10^?6 mm³ N^?1 m^?1 and for the nc-TiC/a-C one it was 0.28 × 10^?6 mm³ N^?1 m^?1.     

热喷涂Fe基非晶合金涂层的微观结构与摩擦磨损行为

分别采用超音速火焰喷涂工艺和爆炸喷涂工艺,在Q235不锈钢基体上制备Fe基非晶合金涂层,对比研究这2种非晶合金涂层在室温下的干摩擦磨损特性,并探讨摩擦磨损机理.结果表明,与超音速火焰喷涂工艺制备的Fe基非晶合金涂层相比,采用爆炸喷涂工艺制备的涂层更致密,孔隙率为2.1％,显微硬度更高,平均硬度高达1 095.6 HV,且耐磨性更好;并且涂层摩擦因数增至稳定值的时间较短,具有更稳定的摩擦磨损行为.超音速火焰喷涂涂层的磨损形式主要以疲劳磨损为主,而爆炸喷涂涂层的磨损形式为粘着磨损和磨粒磨损的综合作用,并以粘着磨损为主.