功率对激光熔覆(Fe0.25Co0.25Ni0.25Cr0.125Mo0.125)86B14涂层组织均质性及磨损性能的影响*

目前激光熔覆缺少对涂层组织、相结构纵向均质性与性能关联的研究。采用激光熔覆技术,选取不同的激光功率,制备(Fe_0.25Co_0.25Ni_0.25Cr_0.125Mo_0.125)₈₆B₁₄ 高熵合金涂层;借助电子探针(EPMA)、扫描电子显微镜(SEM)、能谱仪(EDS)和 X 射线衍射仪(XRD)等观察涂层微观组织与物相纵向分布,利用显微硬度计和摩擦磨损试验机测试涂层不同深度部位显微硬度及磨损性能,分析激光功率对熔覆(Fe_0.25Co_0.25Ni_0.25Cr_0.125Mo_0.125)₈₆B₁₄ 涂层纵向组织、物相分布影响规律及磨损性能。结果表明：三种功率下,涂层均由 BCC+FCC 相、硬质相 Mo₂B 组成,Mo₂B 在枝晶间富集。随着功率的增加,涂层中底部显微组织由细枝晶向粗大的柱状晶转变。三种涂层硬度均由表及里先增加后降低,摩擦因数先降低后增加;但是当激光功率为 1.6 kW 时,涂层呈现以 BCC 相为主的 FCC+BCC 双相结构,且由表及里 BCC 相含量不断增加、Mo₂B 含量逐渐减少,涂层组织均质化最高,摩擦因数变化梯度最小,耐磨损性能最佳。激光功率会影响熔覆高熵合金耐磨涂层均质性,进而影响摩擦性能的稳定性。     

激光辅助热喷涂NiCoCrAlYTa/ZrO2/BaF2·CaF2涂层的组织及性能∗

高温耐磨涂层是航空发动机关键摩擦副可靠使用的重要保障,鉴于其服役环境日益严苛复杂,进一步提高涂层的高温耐磨性能是十分必要的。利用激光辅助热喷涂技术制备 NiCoCrAlYTa / ZrO₂ / BaF₂·CaF₂ 高温耐磨涂层,利用 SEM、EDS 分析高温耐磨涂层的横截面微观组织及化学成分,研究 ZrO₂ / BaF₂·CaF₂质量分数、激光功率及扫描速度对耐磨涂层微观组织、力学性能及高温耐磨性能的影响。结果表明：激光辅助处理可以诱导耐磨涂层表面形成具有树枝状结构的 ZrO₂陶瓷层; 当激光功率为 80 W,扫描速度为 8 mm / s,喷涂粉末为 75 wt.% NiCoCrAlYTa+25 wt.% ZrO₂ / BaF₂·CaF₂时,制备涂层的微观组织、综合力学性能及高温耐磨性能达到最好;在此工艺参数下,涂层顶部的 ZrO₂ 陶瓷层最为致密均匀,其平均纳米硬度为 13.6 GPa,平均弹性模量为 182.5 GPa,800 ℃时的磨损率为 2.7×10^?5 mm³ ·N^?1 ·m^?1 。将高温耐磨涂层的组分设计与激光辅助热喷涂工艺相结合,可为提高涂层综合性能的提供解决途径。     

煤油流量对NiCrBSi-CrSi2涂层微观结构及高温磨损性能的影响

在12CrMoVG基体上通过超音速火焰喷涂(HVOF)技术,分别采用不同煤油流量制备了NiCrBSi-CrSi₂复合涂层。利用 XRD、SEM、EDS、Raman、维氏显微硬度计、电子拉伸试验机和高温旋转式摩擦磨损试验机分别表征了不同煤油流量下涂层物相、组织结构、力学性能和高温摩擦磨损性能。结果表明: 不同煤油流量涂层的物相组成基本相同,均有γ-Ni、Ni₃B、Cr₂B、CrSi₂和Cr₅Si₃,但随着煤油流量升高,涂层中的CrSi₂和Cr₂B的部分会分别转变为Cr₅Si₃和CrB相。涂层显微硬度和结合强度随着煤油流量的升高均呈现先增后减的趋势,孔隙率和磨损率表现出先减后增的趋势。当煤油流量为30 L/h时,粉末熔融效果最好,涂层的孔隙率最低为0.17 %,显微硬度较高达到569 HV_0.3,结合强度较高为59 MPa,磨损率最低为2.84×10_-14 m₃^/(N.m)。磨痕表面产生的 Cr₂O₃、SiO₂和NiCr₂O₄等氧化物以及较高的涂层硬度使得30 L/h的涂层显示出最优的耐高温摩擦磨损性能。涂层的磨损机制以氧化磨损和黏着磨损为主。     

Cu-Fe64Ni32Co4合金显微组织及热物理性能研究

本研究利用相图计算的CALPHAD方法和真空电弧熔炼技术,设计并制备了Cu_x(Fe_0.64Ni_0.32Co_0.04)_100-x(x=30, 45, 60, wt. %)系列合金。实验研究了该系列合金在不同热处理工艺时的显微组织,热导率以及热膨胀系数。研究结果表明：Cu-Fe₆₄Ni₃₂Co₄系列合金在600 °C和800 °C时效处理后均为fcc富铜相和fcc富因瓦(铁镍钴)相组成的各向同性的多晶合金。该系列合金在1000 °C淬火并在600 °C时效处理50 h后,其热膨胀系数变化范围为6.88~12.36×10_-6 K_-1;热导率变化范围为22.91~56.13 W.m_-1.K_-1;其热导率明显高于因瓦合金,其中Cu₃₀(Fe_0.64Ni_0.32Co_0.04)₇₀与 Cu₄₅(Fe_0.64Ni_0.32Co_0.04)₅₅合金的热膨胀系数可以与电子封装中半导体材料的热膨胀系数相匹配。     

纳米柱状多孔WO3- x /TiO2 薄膜的电致变色性能

采用反应磁控溅射在掠射角度α=0°和α=80°的条件下制备氧化钨（WO_3-x）薄膜,然后在其表面沉积二氧化钛（TiO₂）。利用X射线衍射仪（XRD）、场发射扫描电镜（FE-SEM）和X射线光电子能谱仪（XPS）对WO_3-x/TiO₂薄膜的晶体结构、表面/断面形貌以及表面化学成分进行表征。在三电极体系1 mol/L LiClO₄/PC溶液中,采用电化学工作站和紫外-可见分光光度计测试了WO_3-x/TiO₂薄膜的电致变色性能。XRD结果表明,WO_3-x/TiO₂薄膜为非晶态结构,与掠射角度无关。当掠射角度为80°时,获得了纳米柱状多孔薄膜。从 W 4f和Ti 2p的XPS谱图确认氧化钨为亚化学计量比的WO_3-x,而氧化钛为满足化学计量比的TiO₂。与致密薄膜相比,纳米柱状多孔薄膜需要较低的驱动电压且具有较快的响应速度。纳米柱状多孔薄膜的电荷容量为83.78 mC,是致密薄膜电荷容量30.83 mC的2倍以上。在±1.2 V驱动电压下,注入和脱出离子扩散速率分别为D_in=5.69×10^-10 cm²/s和D_de= 5.08×10^-10 cm²/s。与纯WO₃薄膜相比,WO_3-x/TiO₂薄膜的电致变色循环稳定性更好。纳米柱状多孔薄膜在可见光范围内具有较大的光调制幅度,因此其光密度变化（ΔOD）大于致密薄膜。     

基于第一性原理的石榴石型Li7La3Zr2O12 固态电解质的设计与合成

基于密度泛函理论（DFT）的第一原理方法计算了四方相和立方相中2种不同的Li₇La₃Zr₂O₁₂（LLZO）固体电解质材料的能带结构,晶格参数,态密度和成键特性。基于理论计算结果,通过电子结构特性解释了四面体相的离子电导率低于立方相的离子电导率的原因。基于LLZO的第一性原理计算,设计了2种晶体结构的LLZO材料,并通过高温固相法制备并分析了不同烧结时间的LLZO颗粒的性能。探索了合成工艺参数对Li₇La₃Zr₂O₁₂性能的影响。立方晶Li₇La₃Zr₂O₁₂（C-LLZO）的平均晶格大小为a=b=c=1.302 246 nm,而四方Li₇La₃Zr₂O₁₂（T-LLZO）的平均晶格大小为a=b=1.313 064 nm,c=1.266 024 nm。在1000 ℃下烧结12 h的C-LLZO为纯立方相,在室温（25 ℃）下最大离子电导率为9.8×10^-5 S·cm^-1。T-LLZO在室温（25 ℃）下的离子电导率为5.96×10^-8 S·cm^-1,在800 ℃下烧结6 h具有纯的四方相结构,与计算结果基本吻合。     

激光比能对Fe2B激光熔覆涂层微观组织与性能的影响

利用粉末喷射激光熔覆以球形硼铁粉末为原材料成功制备了 Fe₂B 金属间化合物涂层。 采用金相显微镜 (OM)、 X 射线衍射仪 (XRD)、 扫描电镜 ( SEM)、 电子探针 (EPMA)、 显微维氏硬度计及摩擦磨损试验机对涂层的组织与性能进行了表征。 结果表明: 当激光比能控制在 3. 00×10 ⁸ kJ/ m ² 左右时, 采用粉末喷射激光熔覆能制备较为理想的 Fe₂B 金属间化合物涂层。 制备的单层涂层的物相为 Fe₂B 与 Fe, 显微硬度峰值达 1360 HV_{0. 05} , 涂层组织中大量弥散分布的 Fe₂B 相的生成是涂层具有高硬度的原因。 制备的多层涂层与基体具有良好的冶金结合, 从基体到涂层, 组织经历了一个由平面外延生长组织到胞状晶再到等轴晶的演变过程, 涂层稳定摩擦因数为 0. 385, 磨损率为 5. 67×10 ^-15 m ³ / N·m,表现出良好的耐磨性能, 磨损机制为磨粒磨损与疲劳磨损。     

基于基团贡献法估算(富锂)锂离子电池正极材料Li1+ xM 1- x O2 的热力学性质

富锂Li_1+xM_1-xO₂材料的研究主要集中在其结构和电化学性能上,而很少关注其热力学性能。开发具有高能量密度和容量的新型富锂材料取决于这种材料的结构、热力学性质和电化学性质之间的固有关系。对富锂材料Li_1+xM_1-xO₂的热力学性质了解不足,使得新型Li_1+xM_1-xO₂材料的开发和利用受到限制。鉴于Li_1+xM_1-xO₂材料缺乏热力学数据,根据基团贡献方法的原理对LiAlO₂进行拆分。基于热力学原理,提出了用于估计LiAlO₂的ΔG^θ_f,298、ΔH^θ_f,298和C_p的数学模型。采用基团贡献法估算了56种固体无机化合物的ΔG^θ_f,298和ΔH^θ_f,298以及54种固体无机化合物的C_p,298,以检验该模型的可靠性和适用性。利用基团贡献法估算了固体无机化合物的数学模型。利用基团贡献法拟合的基团参数选择的实验数据准确可靠。在结果令人满意的基础上,建立了用于估算3种类型的Li_1+xM_1-xO₂材料的ΔG^θ_f,298,ΔH^θ_f,298和C_p的数学模型,并估算了63种常见Li_1+xM_1-xO₂材料的ΔG^θ_f,298、ΔH^θ_f,298和C_p,298。     

硅对高硅奥氏体不锈钢析出相的影响

采用XRD、TEM和压痕变形等方法研究了Si含量（4%~8%,质量分数）对高硅奥氏体不锈钢（ZeCorn）显微组织的影响。结果表明,Si含量的增加会导致ZeCor合金的相组成发生变化：ZeCor-4%Si合金组织为单相奥氏体（γ相）,ZeCor-6%Si合金主要含γ相和少量σ相,在ZeCor-8%Si合金中主要析出Cr₃Ni₅Si₂相和少量σ相。此外,Cr₃Ni₅Si₂与σ相相比具有更高的硅、镍含量。显微硬度HV高达7840 MPa的Cr₃Ni₅Si₂相是典型的硬脆相,该相的析出将大大提高ZeCor-8%Si合金中γ基体的显微硬度。ZeCor合金中γ基体的强化机制如下：固溶强化是ZeCor-6%Si合金的主要强化机制,而Si的固溶强化和Cr₃Ni₅Si₂的析出强化机制都大大提高ZeCor-8%Si合金中的γ基体的显微硬度。在ZeCor-8%Si合金中,Cr₃Ni₅Si₂相起显著作用。     

超音速大气等离子喷涂TiB2-SiC涂层的抗氧化性及耐熔盐腐蚀性能

采用超音速大气等离子喷涂制备全包覆TiB₂-SiC涂层,研究了TiB₂-SiC涂层在400和800 ℃的氧化性能,并探究其氧化机理。对TiB₂-SiC涂层在900 ℃下的抗铝熔盐腐蚀性能进行研究,并探讨其耐熔盐腐蚀机理。结果表明,超音速大气等离子喷涂制备的TiB₂-SiC涂层具有良好的抗氧化性,在400 ℃的氧化速率常数为1.92×10^-5 mg²·cm^-4·s^-1,在800 ℃的氧化速率常数为1.82×10^-4 mg²·cm^-4·s^-1。超音速大气等离子喷涂制备的TiB₂-SiC涂层在900 ℃下具有良好的抗熔盐腐蚀性能,熔盐腐蚀后TiB₂-SiC涂层都保持致密结构,未发生涂层的开裂及剥落。     

Microstructure and properties of Cr3C2-modified nickel-based alloy coating deposited by plasma transferred arc process

The nickel-based alloy with 30 wt.% chromic carbide (Cr₃C₂) particles has been deposited on Q235-carbon steel (including 0.12 wt.% C) using plasma transferred arc (PTA) welding machine. The microstructure and properties of the deposited coatings were investigated using optical microscope, scanning electron microscope (SEM) equiped with X-ray energy spectrometer (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), microhardness testes, and sliding wear test. It was found that the γ(Ni, Fe), M₇(C,B)₃, Ni₄B₃, and (Cr,Fe)₂B phases existed in the Cr₃C₂-free nickel-based alloy coating obtained by PTA process. The typical hypoeutectic structure and composition segregation in the solid solution could be found clearly. The addition of 30 wt.% Cr₃C₂ particles led to the existing of Cr₃C₂ phase and the microstructure changing from hypoeutectic structure into hypereutectic structure. The composition segregation in the solid solution could not be found clearly. The average microhardness of the Cr₃C₂-free nickel-based alloy coating increased by 450-500 HV after the addition of 30 wt.% Cr₃C₂ particles. The partial dissolution of Cr₃C₂ particles led to the enrichment of carbon and chromium in the melten pool, and hence caused the formation of more chromium-rich carbides after the solidification process. The undissolved Cr₃C₂ particles and the increasing of chromium-rich carbides was beneficial to enhance the hardness and wear resistance of the Cr₃C₂-modified nickel-based alloy coating deposited by PTA process.     

Preparation and wear performance of NiCr/Cr3C2-NiCr/hBN plasma sprayed composite coating

NiCr clad hexagonal BN powder (NiCr/hBN) was added to NiCr/Cr₃C₂ feedstock to improve the tribological properties of chromium carbide nichrome coating. The microstructure, flowability and apparent density of the composite powder, as well as the structure and mechanical properties of the plasma sprayed coating were characterized. The friction and wear behavior of the NiCr/Cr₃C₂-NiCr/hBN coating from ambient temperature up to 800 °C was evaluated on a ball-on-disk wear tester and compared with that of NiCr/Cr₃C₂ coating and NiCr/Cr₃C₂-NiCr/BaF₂·CaF₂ coating. The results show that NiCr cladding can reduce the decarburization of Cr₃C₂ and oxidation of hBN during the thermal spray. The main wear mechanisms of the NiCr/Cr₃C₂-NiCr/hBN composite coating are ploughing and adhesive wear. Layered hexagonal BN particle reduce the direct contact and severe adhesion between friction pairs, thus decreasing the friction coefficient. The NiCr/Cr₃C₂-NiCr/hBN composite coating shows a promising application in the high temperature environment with the request of both wear resistance and friction reduction.     

煤油流量对HVOF喷涂WC-12Co/NiCrBSi复合涂层显微组织与性能的影响

在 CrZrCu 基体上电镀 Ni 粘结层,通过超音速火焰喷涂(HVOF)技术,采用不同煤油流量在电镀 Ni 粘结层上制备了 WC-12Co / NiCrBSi 复合涂层。 利用 XRD、SEM、Raman、维氏显微硬度计、电子拉伸试验机和球盘式摩擦磨损试验机考察了不同煤油流量下涂层相组成、组织结构、力学性能和高温摩擦磨损性能。 结果表明:不同涂层的物相组成基本相同,喷涂过程中发生了一定程度的分解脱碳生成了 W2C,以及少量的 Cr₇C₃ 和 Co₃W₃C 相;随着煤油流量升高,涂层硬度提高,涂层孔隙率和耐磨性表现出先降低后升高趋势,致密的结构与较高的硬度有利于提高涂层的耐磨性;煤油流量为 26 L/ h 的工艺下制备的涂层孔隙率最低,为 0. 11%,硬度较高达到 927. 0 HV_{0. 3} ,摩擦因数最低约为 0. 46,磨损率最低为 2. 83×10^-15 m³ / (N·m),抗粘着磨损性能最好。     

Mechanical and tribological properties of plasma-sprayed Cr3C2-NiCr, WC-Co, and Cr2O3 coatings

Mechanical properties such as Young’s moduli and fracture toughness of plasma-sprayed Cr₃C₂-NiCr, WC-Co and Cr₂O₃ coatings were measured. The tribological properties of the three kinds of coatings were investigated with a block-on-ring self-mated arrangement under water-lubricated sliding. Furthermore, the influences of the mechanical properties on the tribological properties of the coatings were also examined. It was found that the Young’s moduli, bend strengths and fracture toughness of the coatings were lower than the corresponding bulk materials, which may be attributed to the existence of pores and microcracks in the coatings. Among the three kinds of coatings, the magnitude of wear coefficients, in decreasing order, is Cr₃C₂-NiCr, WC-Co and Cr₂O₃, and the wear coefficient of Cr₂O₃ coating was less than 1 × 10⁻⁶mm³N⁻¹m⁻¹. The wear mechanisms of the coatings were explained in terms of microcracking and fracturing, and water deteriorated wear performance of the coatings. The higher the fracture toughness and the lower the porosity and length of microcracking of the coating, the more the wear-resistance of the coating.     

High rate deposition of thick CrN and Cr2N coatings using modulated pulse power (MPP) magnetron sputtering

As a variation of high power pulsed magnetron sputtering technique, modulated pulse power (MPP) magnetron sputtering can achieve a high deposition rate while at the same time achieving a high degree of ionization of the sputtered material with low ion energies. These advantages of the MPP technique can be utilized to obtain dense coatings with a small incorporation of the residual stress and defect density for the thick coating growth. In this study, the MPP technique has been utilized to reactively deposit thick Cr₂N and CrN coatings (up to 55 μm) on AISI 440C steel and cemented carbide substrates in a closed field unbalanced magnetron sputtering system. High deposition rates of 15 and 10 μm per hour have been measured for the Cr₂N and CrN coating depositions, respectively, using a 3 kW average target power (16.7 W/cm² average target power density), a 50 mm substrate to target distance and an Ar/N₂ gas flow ratio of 3:1 and 1:1. The CrN coatings showed a denser microstructure than the Cr₂N coatings, whereas the Cr₂N coatings exhibited a smaller grain size and surface roughness than those of the CrN coatings for the same coating thickness. The compressive residual stresses in the CrN and Cr₂N coatings increased as the coating thickness increased to 30 μm and 20 μm, respectively, but for thicker coatings, the stress gradually decreased as the coating thickness increased. The CrN coatings exhibited an increase in the scratch test critical load as the thickness was increased. Both CrN and Cr₂N coatings showed a decrease in the hardness and an increase in the sliding coefficient of friction as the coating thickness increased from 2.5 to 55 μm. However, the wear rate of the CrN coatings decreased significantly as the coating thickness was increased to 10 μm or higher. The 10-55 μm CrN coating exhibited low wear rates in the range of 3.5-5 × 10⁻⁷ mm³ N⁻¹ m⁻¹. To the contrary, the Cr₂N coating exhibited relatively low wear resistance in that high wear rates in the range of 3.5 to 7.5 × 10⁻⁶ mm³ N⁻¹ m⁻¹ were observed for different thicknesses.     

Microstructure and abrasive wear performance of chromium carbide reinforced Ni3Al matrix composite coating

A Ni-Al-Cr₃C₂ welding wire was produced by metal-powder-core technique. When the welding wires were welded on the surface of carbon steel, under the effect of the physical heat of arc, Ni reacted with Al to form Ni₃Al and carbide particles reinforced Ni₃Al matrix composite was formed. Cr₃C₂ was decomposed during welding and dispersed Cr₇C₃ with stripe shape formed, which strengthened the matrix significantly. The Cr₇C₃-Ni₃Al interface has broadened into a zone of interdiffusion and a new phase M₂₃C₆, which indicates that a good bond has been formed. The pin-abrasion wear test showed that the abrasion resistance of Cr₇C₃/Ni₃Al composite is six times higher than that of Stellite12 alloy at room temperature. The good wear resistance of Cr₇C₃/Ni₃Al composite coating can be attributed to large volume fraction of carbides, high hardness, and good phases interface bond.     

Microstructure and wear property of laser-clad Co3Mo2Si/Coss wear resistant coatings

Novel wear resistant Co₃Mo₂Si/Co_ss coatings consisting of a microstructure of hard and strong Co₃Mo₂Si intermetallic phases embedded in the ductile Co-base matrix were fabricated on austenite stainless steel by the laser cladding process from the Co-Mo-Si powder blend precursor. The microstructures of the coatings were characterized by optical microscopy (MO), X-ray diffraction (XRD), and scanning electron microscopy (SEM) with an energy-dispersive X-ray analysis (EDX). The wear resistance of the coatings was evaluated in a dry sliding wear test condition at room temperature. Results indicated that the laser-clad Co₃Mo₂Si/Co_ss coatings exhibited very excellent wear resistance against abrasive and adhesive wear.     

Cr3C2-NiCr and WC-Ni thermal spray coatings as alternatives to hard chromium for erosion-corrosion resistance

Cr₃C₂-NiCr and WC-Ni coatings are widely used for wear applications at high and room temperature, respectively. Due to the high corrosion resistance of NiCr binder, Cr₃C₂-NiCr coatings are also used in corrosive environments. The application of WC-Ni coatings in corrosive media is not recommended due to the poor corrosion resistance of the (pure Ni) metallic matrix. It is well known that the addition of Cr to the metallic binder improves the corrosion properties. Erosion-corrosion performance of thermal spray coatings is widely influenced by ceramic phase composition, the size of ceramic particles and also the composition of the metallic binder. In the present work, two types of HVOF thermal spray coatings (Cr₃C₂-NiCr and WC-Ni) obtained with different spray conditions were studied and compared with conventional micro-cracked hard chromium coatings. Both as-sprayed and polished samples were tested under two erosion-corrosion conditions with different erosivity. Tungsten carbide coatings showed better performance under the most erosive condition, while chromium carbide coatings were superior under less erosive conditions. Some of the tungsten carbide coatings and hard chromium showed similar erosion-corrosion behaviour under more and less erosive conditions. The erosion-corrosion and electrochemical results showed that surface polishing improved the erosion-corrosion properties of the thermally sprayed coatings. The corrosion behaviour of the different coatings has been compared using Electrochemical Impedance Spectroscopy (EIS) and polarization curves. Total material loss due to erosion-corrosion was determined by weight loss measurements. An estimation of the corrosion contribution to the total weight loss was also given.     

Influence of normal load and sliding speed on the tribological property of amorphous carbon nitride coatings sliding against Si3N4 balls in water

Amorphous carbon nitride (a-CN_x) coatings were deposited on Si₃N₄ disks by an ion beam assisted deposition system. The composition, structure and hardness of the a-CN_x coatings were characterized by Auger electronic spectroscopy, Raman spectroscopy and nano-indentation tester, respectively. The influences of normal load and sliding speed on the friction coefficients and the specific wear rates for the a-CN_x/Si₃N₄ tribo-pairs were investigated and analyzed synthetically by ball-on-disk tribometer. The worn surfaces were observed by optical microscope. The results showed that the a-CN_x coatings contained 12 at.% nitrogen, and their structure was a mixture of sp²and sp³ bonds. The a-CN_x coatings’ nanohardness was 29 GPa. The influence of sliding speed on the friction coefficients and the specific wear rate of the CN_x coatings was more obvious than that of normal load. The friction coefficients and the specific wear rate of the CN_x coatings decreased as the sliding speed increased. At a sliding speed higher than 0.1 m/s, the friction coefficients were less than 0.04. The specific wear rates of the a-CN_x coatings were higher than those of Si₃N₄ balls at a sliding speed below 0.1 m/s, while the specific wear rates of the a-CN_x coatings and the Si₃N₄ balls all fluctuated around a lower level of 10^− 8 mm³/Nm as the sliding speed increased beyond 0.2 m/s. To describe the wear behavior of a-CN_x coatings sliding against Si₃N₄ balls in water with normal loads of 3-15 N and sliding speeds of 0.05-0.5 m/s, the wear-mechanism map for the a-CN_x/Si₃N₄ tribo-pairs in water was developed.