Deposition and characterization of CrN/Si3N4 and CrAlN/Si3N4 nanocomposite coatings prepared using reactive DC unbalanced magnetron sputtering

Nanocomposite coatings of CrN/Si₃N₄ and CrAlN/Si₃N₄ with varying silicon contents were synthesized using a reactive direct current (DC) unbalanced magnetron sputtering system. The Cr and CrAl targets were sputtered using a DC power supply and the Si target was sputtered using an asymmetric bipolar-pulsed DC power supply, in Ar + N₂ plasma. The coatings were approximately 1.5 μm thick and were characterized using X-ray diffraction (XRD), nanoindentation, X-ray photoelectron spectroscopy and atomic force microscopy. Both the CrN/Si₃N₄ and CrAlN/Si₃N₄ nanocomposite coatings exhibited cubic B1 NaCl structure in the XRD data, at low silicon contents (< 9 at.%). A maximum hardness and elastic modulus of 29 and 305 GPa, respectively were obtained from the nanoindentation data for CrN/Si₃N₄ nanocomposite coatings, at a silicon content of 7.5 at.%. (cf., 24 and 285 GPa, respectively for CrN). The hardness and elastic modulus decreased significantly with further increase in silicon content. CrAlN/Si₃N₄ nanocomposite coatings exhibited a hardness and elastic modulus of 32 and 305 GPa, respectively at a silicon content of 7.5 at.% (cf., 31 and 298 GPa, respectively for CrAlN). The thermal stability of the coatings was studied by heating the coatings in air for 30 min in the temperature range of 400-900 °C. The microstructural changes as a result of heating were studied using micro-Raman spectroscopy. The Raman data of the heat-treated coatings in air indicated that CrN/Si₃N₄ and CrAlN/Si₃N₄ nanocomposite coatings, with a silicon content of approximately 7.5 at.% were thermally stable up to 700 and 900 °C, respectively.     

Influence of Al Contents on the Microstructure, Mechanical, and Wear properties of Magnetron Sputtered CrAlN Coatings

CrAlN (0 < x < 0.1) coatings were deposited on SA304 substrate by a reactive magnetron sputtering. The microstructure and composition of the as-deposited coatings were systematically characterized by field emission scanning electron microscopy/EDS and atomic force microscopy, and the phase formation by x-ray diffraction (XRD). The hardness of the coatings was investigated using nanoindentation, while wear properties were investigated using pin-on-disk tribometer. XRD study reveals that the deposited CrAlN coatings crystallized in the cubic B1 NaCl structure. The minimum and maximum hardness of the coatings are found to be 15.28 and 18.81 GPa, respectively. The COF and wear rate are found to be 0.48 and 2.25 × 10^?5 mm³/N · m, which is lower than the CrN coatings deposited and characterized under the same environment (0.63 and 2.25 × 10^?5 mm³/Nm).     

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%.     

Synthesis and characterization of multilayer CrN/ZrN coatings

In this study, multilayer CrN/ZrN coatings with various bi-layer periods (δ) were deposited by closed-field unbalanced magnetron sputtering and their compositions, crystalline structures and morphologies were characterized by auger electron spectroscopy (AES), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Additionally, the mechanical properties of the coatings were characterized by nano-indentation and wear tests. The XRD results showed that the diffraction peak of multilayer CrN/ZrN coatings is observable between the CrN (111) and the ZrN (111). This peak has a strong tendency to increase the intensity and sharpen the width as the substrate rotation speed increases, indicating that the grain size of the multilayer CrN/ZrN coatings gradually increases. The hardness of films was dependent on the bi-layer period (δ), and the maximum hardness and elastic modulus were approximately 31.8 GPa and 321.5GPa, respectively. Moreover, the results of the wear tests showed that the multilayer CrN/ZrN coatings exhibited greatly improved wear resistance compared to the monolithic CrN coatings.     

Effects of Al Content on Microstructure and Mechanical Property of CrAlN Coating Synthesized by Reactive Magnetron Sputtering

A series of CrAlN coatings with different Al content were synthesized on high-speed steel(M2)substrate by reactive direct current(DC)magnetron sputtering.The influences of Al content on the microstructure and mechanical property of CrAlN coatings were studied by scanning electron microscopy(SEM),X-ray diffraction(XRD),energy dispersive spectrum(EDS)and nano-indentation techniques,respectively.The results indicate that the coatings exhibit only fcc c-CrN phase when Al content is less than 65 at%,and fcc c-CrN and c-AlN phases when Al content is 78 at%.The coating with Al content of 60 at%exhibits high hardness and elastic modulus.The maximum hardness and elastic modulus values could reach 36.8 GPa and 459.5 GPa,respectively.     

Ti基与Cr基氮化物涂层的抗氧化性能

选用TiN,TiAlN,CrN和CrAlN 4种涂层材料,使用电阻炉对试样加热并保温,进行抗氧化性能实验,利用SEM、EDS和XRD获得了氧化结果。结果表明:Ti基涂层的氧化机制以O原子向涂层内部扩散为主;Cr基涂层的抗氧化机制为N原子和Cr离子向涂层表面的扩散所形成的微孔诱发的氧化;Cr基涂层比Ti基涂层具有较好的抗氧化性;Al的加入使得TiAlN与CrAlN涂层的氧化性能和高温后硬度提高,特别是CrAlN氧化后生成的致密Cr2O3和Al2O3混合氧化物使其抗氧化性能达到最优;氧化及涂层与基体的热涨失配使得几类涂层最终开裂失效;四种涂层的抗氧化能力为CrAlN>TiAlN>CrN>TiN。     

Structural and mechanical stability upon annealing of arc-deposited Ti-Zr-N coatings

Ti-Zr-N coatings were formed by the method of vacuum arc deposition using combined Ti and Zr plasma flows in a N₂ atmosphere at different ratios of arc currents of Ti and Zr cathodes. After deposition, obtained samples were annealed in vacuum at the temperature of 850 °C. The element and phase composition, residual stresses and nanohardness were studied by Auger-Electron Spectroscopy, X-ray diffraction (XRD) and nanoindentation, respectively.XRD analysis reveals the formation of ternary Ti-Zr-N nitride coatings with the structure of solid solutions. It is shown that Ti-Zr-N coatings possess high hardness in comparison with TiN and ZrN binary nitrides. An increase in hardness is observed with increasing Zr content. However, it is established that after annealing coatings keep better stability of hardness with decrease of Zr content. The intrinsic stress in the as-deposited coatings is found to be largely compressive (− 4 GPa) and almost independent of Zr content, but much higher than in ZrN and TiN binary nitrides (− 2 GPa). After annealing, a significant stress relaxation is observed in all coatings due to relief of growth-induced point defects. Stress analysis on as-grown and annealed samples enabled us to determine the stress-free lattice parameter a₀. This latter is expanded by ∼ 0.4-0.7% as compared to Vegard's law.The thermal stability of Ti-Zr-N coatings will be discussed in terms of evolution and interdependence between structure, composition and hardness after annealing.     

Microstructure and mechanical properties of pulsed DC magnetron sputtered nanocomposite Cr-Cu-N thin films

The nanocomposite Cr-Cu-N thin films have been deposited at a substrate temperature of 250 °C by a bipolar asymmetric pulsed DC reactive magnetron sputtering process. Different Cu contents ranging from 0.4 to 14.9 at.% were achieved. The structures of Cr-Cu-N thin films were analyzed by XRD. The surface and cross sectional morphologies of thin films were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The nanoindentation and scratch tests were adopted to evaluate the mechanical and tribological properties of Cr-Cu-N coatings. The influences of Cu content on the structure, mechanical and tribological properties of Cr-Cu-N coatings were explored. It is observed that the columnar structure no longer exists when the Cu content exceeds 10.9 at.%. The stability of CrN phase in the coating is influenced by the Cu content. The scratching coefficient of thin films decreases with increasing Cu content. Sufficient adhesion and tribological properties of Cr-Cu-N coatings are achieved. The maximum average hardness around 20 GPa and scratching coefficient around 0.1 are found in the coatings with around 2.1 to 2.6 at.% Cu in this work.     

Structure and properties of selected (Cr–Al–N,TiC–C,Cr–B–N) nanostructured tribological coatings

The paper will present the state-of-art in the process, structure and properties of nanostructured multifunctional tribological coatings used in different industrial applications that require high hardness, toughness, wear resistance and thermal stability. The optimization of these coating systems by means of tailoring the structure (graded, superlattice and nanocomposite systems), composition optimization, and energetic ion bombardment from substrate bias voltage control to provide improved mechanical and tribological properties will be assessed for a range of coating systems, including nanocrystalline graded Cr_1−xAl_xN coatings, superlattice CrN/AlN coatings and nanocomposite Cr–B–N and TiC/a-C coatings. The results showed that the superlattice CrN/AlN coating exhibited a super hardness of 45 GPa when the bilayer period Λ was about 3.0 nm. Improved toughness and wear resistance have been achieved in the CrN/AlN multilayer and graded CrAlN coatings as compared to the homogeneous CrAlN coating. For the TiC/a-C coatings, increasing the substrate bias increased the hardness of TiC/a-C coatings up to 34 GPa (at −150 V) but also led to a decrease in the coating toughness and wear resistance. The TiC/a-C coating deposited at a −50 V bias voltage exhibited an optimized high hardness of 28 GPa, a low coefficient of friction of 0.19 and a wear rate of 2.37 × 10⁻⁷ mm³ N⁻¹ m⁻¹. The Cr–B–N coating system consists of nanocrystalline CrB₂ embedded in an amorphous BN phase when the N content is low. With an increase in the N content, a decrease in the CrB₂ phase and an increase in the amorphous BN phase were identified. The resulting structure changes led to both decreases in the hardness and wear resistance of Cr–B–N coatings.     

同步脉冲偏压对HiPIMS技术低温沉积CrN涂层结构及性能影响*

针对高性能 CrN 涂层无法实现低温可控制备的技术瓶颈,利用具备高溅射材料离化率的高功率脉冲磁控溅射技术,调控同步脉冲偏压,改善涂层生长动力学条件,实现 CrN 涂层的低温可控沉积。开展同步脉冲偏压与涂层化学组成、组织结构、 力学、摩擦学及耐腐蚀性能间关联关系研究。同步脉冲偏压在提升沉积离子束流迁移能的同时可显著降低荷能 Ar⁺ 对成膜表面的持续轰击作用,达到改善涂层致密性及膜基结合力的目的。此外,沉积 CrN 涂层晶粒细化显著,硬度及弹性模量明显升高,最高可达 13.8 GPa、236.7 GPa。涂层力学性能优化及致密性提升显著改善了摩擦学与耐腐蚀性能,涂层磨损率最低可达 2.49×10^?15 m³ / (N·m),同时涂层可耐受 120 h 中性盐雾腐蚀环境考核。为实现高性能 CrN 涂层的低温可控制备,扩展其在温度敏感基体领域的适用范围提供了新的设计思路与技术支撑。     

Thermal stability behaviors of Cr(N,O)/CrN double-layered coatings by TGA/DTA analysis

In this study, Cr(N,O)/CrN double-layered coatings were synthesized using the cathodic arc deposition (CAD) process. CrN film was first deposited onto a substrate as an interlayer to ensure better adhesion, and Cr(N,O) film was subsequently deposited on top of the CrN layer as the surface layer. Variation in the Cr(N,O) coating composition was achieved through changing the O₂/N₂ flow ratio during the last stage of processing. Phase structure, chemical composition, and morphology of the resulting coatings were analyzed and observed using the X-ray diffractometer, Auger electron spectrometer and SEM. In addition, oxidation behavior of the coatings was investigated using TGA/DTA methods. The tests were carried out by increasing temperature up to 1000 °C in ambient air. With the introduction of oxygen gas during the CAD process, a superficial layer was produced in the Cr(N,O) constituent containing CrN and Cr₂O₃ phases. The formation of the oxide phase attributed to the reaction of chromium and oxygen was more favorable than that of chromium and nitrogen. The results also showed that Cr(N,O)/CrN double-layered coatings exhibited superior oxidation resistance at elevated temperature than that of CrN single-layer coated specimen (870 °C vs. 750 °C).     

Effect of Annealing Temperature on Tribological Properties and Material Transfer Phenomena of CrN and CrAlN Coatings

This study evaluates the effects of annealing temperature and of the oxides produced during annealing processes on the tribological properties and material transfer behavior between the PVD CrN and CrAlN coatings and various counterface materials, i.e., ceramic alumina, steel, and aluminum. CrAlN coating has better thermal stability than CrN coating in terms of hardness degradation and oxidation resistance. When sliding against ceramic Al₂O₃ counterface, both CrN and CrAlN coatings present excellent wear resistance, even after annealing at 800 °C. The Cr-O compounds on the coating surface could serve as a lubricious layer and decrease the coefficient of friction of annealed coatings. When sliding against steel balls, severe material transfer and adhesive wear occurred on the CrN and CrAlN coatings annealed at 500 and 700 °C. However, for the CrAlN coating annealed at 800 °C, much less material sticking and only small amount of adhesive wear occurred, which is possibly due to the formation of a continuous Al-O layer on the coating outer layer. The sliding tests against aluminum balls indicate that both coatings are not suitable as the tool coatings for dry machining of aluminum alloys.     

Syntheses and mechanical properties of Cr-Mo-N coatings by a hybrid coating system

Effects of Mo content up to 30.4 at.% on the microstructure and mechanical properties of CrN coatings are reported in this study. Ternary Cr-Mo-N coatings were deposited onto steel substrates (AISI D2) using a hybrid coating method of arc ion plating (AIP) using Cr target and DC magnetron sputtering technique using Mo target in N₂/Ar gaseous mixture. The synthesized Cr-Mo-N coatings formed a substitutional solid solution of (Cr,Mo)N where larger Mo atoms replaced Cr in CrN crystal. The Cr-Mo-N coatings showed increased hardness value of approximately 34 GPa at 21 at.% Mo, compared with 18 GPa for pure CrN. The friction coefficient decreased from 0.49 for pure CrN coating to 0.37 for Cr-Mo-N with 30.4 at.% Mo. This result is believed to be due to tribo-layer formation of MoO₃ which is known to function as a solid lubricant.     

Ti-Al-N 涂层的组织结构与摩擦学性能

目的采用多元等离子体注入与沉积(MPIIID)技术制备Ti-Al-N涂层,系统研究涂层的微观组织结构、力学性能与摩擦学特性。方法借助XRD,XPS,SEM和TEM等,观察分析Ti-Al-N涂层的微观组织结构与物相组成,采用纳米压入试验仪、布氏硬度试验仪、摩擦磨损试验仪和激光共聚焦显微镜等测试分析Ti-Al-N涂层的力学性能、膜基结合力和摩擦磨损性能。结果 Ti-Al-N涂层表现出较高的膜-基结合强度。Al元素掺杂诱发Ti-Al-N涂层发生严重晶格畸变。当Al原子数分数为6.18%时,Ti-Al-N涂层以c-TiAlN相结构为主,表现出超高硬度(达到39.83 GPa);随着Al元素含量增加,涂层中的软质h-TiAlN相结构增多,硬度随之下降。摩擦试验结果表明,低Al含量Ti-Al-N涂层的抗磨损能力良好,其主要磨损机制为磨粒磨损;高Al含量Ti-Al-N涂层的抗磨损能力较差,其主要磨损机制倾向粘着磨损。结论 MPIIID技术成功实现了Ti-Al-N涂层的低温制备与成分调控,低Al含量的Ti-Al-N涂层具有优良的力学性能和优异的抗磨损能力。     

Structural and mechanical properties of AlTiN/CrN coatings synthesized by a cathodic-arc deposition process

Monolayered AlTiN and Multilayered AlTiN/CrN coatings were synthesized by a cathodic-arc deposition process, using TiAl (with 50/50 and 33/67 at.%) and Cr elemental cathodes. The atomic ratio of Al/(Ti + Al) in the AlTiN coatings was reduced to 0.44 and 0.61, respectively, compared with the corresponding Ti₅₀Al₅₀ and Ti₃₃Al₆₇ cathode materials. The multilayered AlTiN/CrN films showed smaller crystallite size, larger lattice strain, higher hardness, higher residual stress, and better adhesion strength as well than the monolayered AlTi films. The multilayered Al_0.35Ti_0.22N_0.43/CrN coating exhibited the highest hardness of about 38 GPa and the highest H³/E*² ratio value of 0.188 GPa, indicating the best resistance to plastic deformation, among all the coatings studied.     

TC4钛合金表面涂层改性:CrN素多层

目的 提高TC4钛合金的硬度和耐磨损性,改善CrN硬质涂层与TC4钛合金的适应性.方法 采用等离子体增强磁控溅射系统,通过调节热丝放电电流,在TC4钛合金基体表面沉积疏密CrN单层和素多层涂层.利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)、纳米压痕仪、洛氏压痕仪、摩擦磨损仪以及台阶仪,表征涂层形貌、成分、物相及性能.采用动电位极化法表征涂层的耐腐蚀性.结果 当热丝放电电流为较低的4 A×4时,沉积的CrN单层涂层为具有针孔、孔洞等缺陷的疏松结构,8 A×4沉积的CrN单层涂层具有致密结构,周期性调节热丝放电电流则获得疏密交替的CrN素多层涂层.CrN涂层均由单一面心立方结构的CrN相组成,疏松CrN单层涂层的衍射晶面为(111)、(200)、(220)及(222),致密CrN单层涂层沿(111)晶面择优生长,随着疏密子层调制比的增大,CrN素多层涂层的(111)衍射峰不断增强.疏松CrN单层涂层的最小H和最大E分别为13.0 GPa和207.5 GPa,调制比为1:4的疏密CrN素多层涂层的最小H和最大E分别为17.0 GPa和257.4 GP.在1470 N载荷下洛式压痕法表明,致密CrN单层涂层的结合强度最低,等级为HF5,其余涂层均为HF1—HF4.CrN涂层的自腐蚀电位较TC4钛合金均发生了正移.结论 CrN硬质涂层可以有效提高TC4钛合金的硬度和耐磨损性,表面得到明显强化.周期性调节等离子体密度所沉积的疏密CrN素多层涂层与单层相比,涂层性能明显改善.     

Thermal stability of superhard Ti-B-N coatings

Ternary transition-metal boron nitride Ti-B-N offers outstanding hardness and thermal stability, which are increasingly required for wear resistant applications, as the protective coatings are subjected to high temperature, causing thermal fatigue. Ti-B-N coatings with chemical compositions close to the quasibinary TiN-TiB₂ tie line and boron contents below ∼ 18 at.% contain a crystalline supersaturated NaCl structure phase, where B substitutes for N. Annealing above the deposition temperature causes precipitation of TiB₂, which influence dislocation mobility and hence the hardness of TiB_0.40N_0.83 remains at a very high level of ∼ 43 GPa with annealing temperature T_a up to 900 °C. Growth of Ti-B-N coatings with B contents above ∼ 18 at.% results in the formation of nm sized TiN and TiB₂ crystallites embedded in a high volume fraction of disordered boundary layer. The compaction of this disordered phase during annealing results in a hardness increase of TiB_0.80N_0.83 coatings from the as-deposited value of ∼ 37 GPa to ∼ 42 GPa at T_a = 800 °C. Excess B during growth of TiB_2.4 coatings causes the formation of bundles of ∼ 5 nm wide TiB₂ subcolumns encapsulated in a B-rich tissue phase. This nanocolumnar structure is thermally stable up to temperatures of ∼ 900 °C, and consequently the hardness remains at the very high level of ~ 48 GPa, as nucleation and growth of dislocations is inhibited by the nm sized columns. Furthermore, the high cohesive strength of the B-rich tissue phase prevents grain boundary sliding.     

High thermal stability of TiAlSiCN coatings with “comb” like nanocomposite structure

The aim of this work was to understand the reasons for the exceptionally high thermal stability of the TiAlSiCN coatings. The hardness of the coatings increased from 41.5 to 43 GPa between 25 and 900 °C, reached a maximum value of 49 GPa at 1000 °C, and then decreased to 37 GPa at 1300 °C. The structural investigations performed before and after annealing at 1000, 1200, and 1400 °C using X-ray diffraction, scanning and transmission electron microscopy (TEM), and high-resolution TEM showed that the as-deposited “comb” like nanocomposite structure, in which (Ti,Al)(C,N) columnar grains, 10–30 nm wide, were separated by a well developed amorphous tissue, possessed a very high thermal stability as its dominant cubic phase was stable in the temperature range of 25–1400 °C. Further thorough characterization by means of energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy revealed structural modifications inside crystalline and amorphous phases during annealing in vacuum. Such modifications associated with a short-range rearrangement of elements are shown to be responsible for the high hardness of the TiAlSiCN coatings observed up to 1300 °C, with peak hardness at 1000 °C.     

TiSiN nanocomposite coatings by chemical vapor deposition in a fluidized bed reactor at atmospheric pressure (AP/FBR-CVD)

TiSiN nanocomposite coatings were deposited on stainless steel by chemical vapor deposition in a fluidized bed reactor at atmospheric pressure (AP/FBR-CVD) by reaction of TiCl₄ and SiCl₄ with NH₃ at 850 °C. Coatings were characterized by means of GD-OES, XPS and XRD. TiSiN coatings with a Si content of 9 at.% showed a hardness of 28 GPa (the hardness of TiN and SiN_x coatings was around 21 GPa) and a lower oxidation rate under dry air at 600 °C. Our results show for the first time that AP/FBR-CVD can be tuned for the deposition of nanocomposite ceramic coatings.     

有机钼添加剂作用下CrN和CrAlN涂层的摩擦学性能∗

CrN 和 CrAlN 涂层以其优异的力学性能可作为汽车发动机运动部件的保护性涂层使用,然而它与常用润滑油添加剂的相互作用仍需要进一步的研究。 采用磁控溅射技术制备氮化铬(CrN)和氮化铬铝(CrAlN)涂层,利用 X 射线衍射和纳米压痕研究涂层的微结构和机械性能,考察常用摩擦改进剂-烷基二硫代氨基甲酸钼(MoDTC)对涂层摩擦学性能的影响,并通过电子扫描电镜和 X 射线光电子能谱技术等表征探究 MoDTC 的减摩作用机制。 结果表明:与 CrN 涂层相比,CrAlN 涂层结构致密,晶粒细化,机械性能更好。 在添加质量分数为 1%的 MoDTC 后的 PAO 基础油润滑下,表现出更优异的减摩抗磨性能。 对磨痕表面的 XPS 分析表明,在边界润滑条件下,钢/ CrN 和钢/ CrAlN 摩擦运动过程中 MoDTC 均发生化学降解反应,生成一层含二硫化钼(MoS₂ )的润滑膜,且后者产生的 MoS₂ 含量更高,因而表现出更优的摩擦学性能。 研究结果对延长汽车发动机的使用寿命具有指导意义。