Tribological Behavior of Plasma-Sprayed Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-20 wt.%TiO<Subscript>2</Subscript> Coating

Al₂O₃-20 wt.% TiO₂ ceramic coatings were deposited on the surface of Grade D steel by plasma spraying of commercially available powders. The phases and the microstructures of the coatings were investigated by x-ray diffraction and scanning electron microscopy, respectively. The Al₂O₃-20 wt.% TiO₂ composite coating exhibited a typical inter-lamellar structure consisting of the γ-Al₂O₃ and the Al₂TiO₅ phases. The dry sliding wear behavior of the coating was examined at 20 °C using a ball-on-disk wear tester. The plasma-sprayed coating showed a low wear rate (~4.5 × 10^?6 mm³ N^?1 m^?1), which was <2% of that of the matrix (~283.3 × 10^?6 mm³ N^?1 m^?1), under a load of 15 N. In addition, the tribological behavior of the plasma-sprayed coating was analyzed by examining the microstructure after the wear tests. It was found that delamination of the Al₂TiO₅ phase was the main cause of the wear during the sliding wear tests. A suitable model was used to simulate the wear mechanism of the coating.     

Effect of Graphite Addition on Structure and Properties of Ti(CN) Coatings Deposited by Reactive Plasma Spraying

Ti(CN) coatings with graphite addition ranging from 0 to 50 wt.% were prepared using reactive plasma spraying technology and their microstructure, mechanical, and tribological properties were investigated using scanning and transmission electron microscopy, x-ray diffraction analysis, x-ray photoelectron spectroscopy, Vickers microhardness testing, and block-on-ring wear testing. The results showed that graphite addition resulted in crystallite size refinement and an increase in the amount of amorphous phase. The Ti(CN) coatings consisted of a mixture of Ti(CN), graphite, CN _x , and amorphous phases. The hardness first increased then decreased as the graphite content was increased, with a maximum of 1450 HV_0.2 for 30 wt.% graphite addition. The fracture toughness decreased from 4.38 MPa m^1/2 to 2.76 MPa m^1/2 with increasing graphite content. The friction coefficient decreased due to unreacted graphite embedded in the matrix. Also, the wear rate first decreased then increased, with a minimum value of 2.65 × 10^?6 mm³ N^?1 m^?1 for 30 wt.% graphite addition. The wear mechanisms of the Ti(CN) coatings included abrasive, adhesive, and oxidation wear.     

Erosion wear of CrN,TiN, CrAlN,and TiAlN PVD nitride coatings

Four nitride coatings (CrN, ZrN, CrAlN, and TiAlN) were deposited on YT15 cemented carbide by cathode arc-evaporation technique. Microstructural and fundamental properties of these nitride coatings were examined. Erosion wear tests were carried out, the erosion wear of these nitride coatings caused by abrasive particle impact was compared by determining the wear depth and the erosion rates of the coatings. The wear surface features were examined by scanning electron microscopy. Results showed that the coatings with Al (CrAlN and TiAlN) exhibited higher erosion wear resistance over those without Al (CrN and TiN). The H³/E² of the coating seemed to play an important role with respect to its erosion wear in erosion tests. AlTiN and CrAlN coatings being with high H³/E² exhibited lower erosion rates, while CrN coating with low H³/E² showed higher erosion rates under the same test conditions. Analysis of eroded surface of the coatings demonstrated that the TiN and CrN coatings exhibited a typical brittle fracture induced removal process, while AlTiN and CrAlN coatings showed mainly micro cutting and cycle fatigue fracture of material removal mode.     

超声滚压强化对CoCrFeMnNiM(M=Ti,Mo)高熵合金激光熔覆层耐磨性的影响EI北大核心CSCD

CoCrFeMnNi高熵合金较低的硬度和较差的耐磨损性能限制了其在表面工程领域的应用。利用激光熔覆技术制备强化的CoCrFeMnNiM(M=Ti,Mo)高熵合金熔覆层,并通过超声表面滚压(USRE)技术强化熔覆层表面。采用XRD、FSEM、EDS、AFM、显微硬度计和摩擦磨损试验机等研究USRE处理对高熵合金激光熔覆层的微观组织、表面形貌、力学性能和摩擦学性能的影响。结果表明:CoCrFeMnNiTi高熵合金激光熔覆层由面心立方(FCC)结构的固溶体相和TiC原位析出相组成,CoCrFeMnNiMo高熵合金激光熔覆层仍由单一的FCC固溶体相组成。USRE处理后涂层的相构成均未发生变化,但CoCrFeMnNiMo涂层的晶粒尺寸得到更明显的细化。USRE处理降低了高熵合金激光熔覆层的表面粗糙度,提高了残余压应力和显微硬度,并且USRE处理对CoCrFeMnNiMo涂层的效果提升更加显著。经过相同工艺参数的USRE处理后,CoCrFeMnNiTi高熵合金激光熔覆层的体积磨损率由1.90×10^(-4)mm^(3)/(N·m)降低到0.71×10^(-4)mm^(3)/(N·m);但由于磨损机制的转变和表面脆性的增大,CoCrFeMnNiMo高熵合金激光熔覆层的磨损率反而上升。探讨了超声表面滚压处理对高熵合金涂层的适用性,可为高熵合金涂层耐磨性的强化提供参考。     

Methods for increasing the stability of the process and reducing the losses of electrode metal through splashing in CO2 welding

In the present research, a nickel base coating was deposited on an AISI 1020 substrate using a high-velocity oxy-fuel technique. The coating was subsequently heat treated (HT) by means of an oxyacetylene flame. For the conditions evaluated in the present study, it was found that the HT coating has 1.15 times better wear resistance for the lower level of applied load and lower sliding speed (SS), and nearly 50 times better resistance for the highest level of the applied load and highest SS when compared with the non-HT coatings. These results have been attributed to a better distribution of the hardening phases, better cohesion between particles and an increase in hardness, as a consequence of the post-deposition heat treatment process. A severe wear regime was found for all the samples, since the wear rates presented values which were higher than 1 × 10^? 5 mm³/m. The presence of the adhesion, oxidization, three-body abrasion, and cyclical deterioration phenomena, all competing with each other, was noted. For the HT coatings, the wear mechanism was mainly due to the adhesion and oxidisation phenomena, while for the steel counterpart mechanisms such as oxidization, grooving and three-body abrasion were observed.     

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.     

Microstructures and mechanical properties of FeCoCrNi high entropy alloy/WC reinforcing particles composite coatings prepared by laser cladding and plasma cladding

FeCoCrNi HEA coatings with 20% mass fraction of WC reinforcing particles were prepared by two different cladding methods, laser cladding (LC) and plasma cladding (PC). The microstructure of HEA matrix and WC particles of LC and PC coatings were discussed respectively. For HEA matrix, dendritic morphology was observed in both coatings. For WC particles, a few granular (Cr,W)₂C carbides around WC particles in LC coatings, and a large number of crystal and fishbone Fe₃W₃C carbides around WC particles in PC coatings. Mechanical properties as hardness and wear resistance of the two kinds of coatings were also investigated. The interstitial solution strengthening effect of C element is stronger in PC coating, and the hardness of HEA matrix in LC coatings is twice that of in PC coating, which shows a strong retention force on WC particles. The friction coefficient of LC coating is lower and stable, with the volume wear rate of 0.7 × 10⁻⁵ mm⁻³/N·m, showing high wear resistance. PC coatings have poor wear resistance due to decarbonization and oxidation of WC particles and reduction of retention force of HEA matrix, with the volume wear rate of 8.29 × 10⁻⁵ mm⁻³/N·m. The wear mechanism of both coatings were also discussed.     

Friction and wear properties of TiN,TiAlN, AlTiN and CrAlN PVD nitride coatings

Four nitride coatings, TiN, TiAlN, AlTiN and CrAlN were deposited on YG6 (WC + 6 wt.% Co) cemented carbide by cathodic arc-evaporation technique. The friction and wear properties were investigated and compared using ball-on-disc method at high speed with SiC ball as a counter material. The tests were evaluated by scanning electron microscopy, X-ray diffractometer, energy dispersive X-ray, micro hardness tester and an optical profilometer. The results showed that TiN and TiAlN coatings presented lower friction coefficient and lower wear rate, and that high Al content AlTiN and CrAlN coatings didn't present better anti-wear properties in this test. Oxidation and abrasive wear were the main wear mechanism of TiN coating. In spite of the observation of micro-grooves and partial fractures, TiAlN possessed perfect tribological properties compared with the other coatings. High Al content increased the chemical reactivity and aroused severe adhesive wear of AlTiN coating. CrAlN coating presented better properties of anti-spalling and anti-adhesion, but abundant accumulated debris accelerated wear of the coating under this enclosed wear environment.     

The Sliding Wear and Friction Behavior of M50-Graphene Self-Lubricating Composites Prepared by Laser Additive Manufacturing at Elevated Temperature

M50 steel is widely applied to manufacture aircraft bearings where service lives are mainly determined by the friction and wear behaviors. The main purpose of this study is to investigate the tribological behaviors and wear mechanisms of M50-1.5 wt.% graphene composites (MGC) prepared by laser additive manufacturing (LAM) (MGC-LAM) sliding against Si₃N₄ ball from 25 to 550 °C at 18 N–0.2 m/s. XRD, EPMA, FESEM, and EDS mapping were conducted to understand the major mechanisms leading to the improvement in the sliding behavior of MGC-LAM. The results indicated that MGC-LAM showed the excellent friction and wear performance at 25-550 °C for the lower friction coefficient of 0.16-0.52 and less wear rate of 6.1-9.5 × 10^?7 mm³ N^?1 m^?1. Especially at 350 °C, MGC-LAM obtained the best tribological performance (0.16, 6.1 × 10^?7mm³ N^?1 m^?1). It was attributed to the dense coral-like microstructure, as well as the formed surface lubricating structure which is composed of the upper uniform lubricating film with massive graphene and the underneath compacted layer.     

Tribological and Thermal Properties of Mullite Coating Prepared by Atmospheric Plasma Spraying

The primary mullitized andalusite powders were spray-dried and heat-treated to improve sprayable capability. Then, mullite coating was deposited by atmospheric plasma spraying and heat treatment was contributed to recrystallization of the amorphous phase present in the as-sprayed mullite coating. Scanning electron microscopy and x-ray diffraction were used to characterize the microstructure and phase composition of mullite coating. Meanwhile, the phase transition temperature, enthalpy, and specific heat capacity of as-sprayed coatings as well as recrystallized mullite coatings were determined by means of differential scanning calorimetry (DSC). Moreover, tribological properties of as-sprayed coating were investigated by SRV-IV friction and wear tester from 200 to 800 °C. It has been found that the as-sprayed coating possesses good thermal stability. DSC analysis reveals that recrystallization of the glassy phase present in the mullite coating occurs at about 980 °C. The friction coefficient of mullite coating was gradually increased from 0.82 at 200 °C to the highest value of 1.12 at 800 °C, while wear rates of the coating were at the order of 10^?5 mm³/Nm. The as-sprayed coating suffered the most severe wear at 800 °C. The observed wear mechanisms were mainly abrasive wear, brittle fracture, and pulling-out of splats.     

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.     

Investigation of the Effect of Residual Stress Gradient on the Wear Behavior of PVD Thin Films

The control of residual stresses has been seldom investigated in multilayer coatings dedicated to improvement of wear behavior. Here, we report the preparation and characterization of superposed structures composed of Cr, CrN and CrAlN layers. Nano-multilayers CrN/CrAlN and Cr/CrN/CrAlN were deposited by Physical Vapor Deposition (PVD) onto Si (100) and AISI4140 steel substrates. The Cr, CrN and CrAlN monolayers were developed with an innovative approach in PVD coatings technologies corresponding to deposition with different residual stresses levels. Composition and wear tracks morphologies of the coatings were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, atomic force microscopy, x-ray photoelectron spectroscopy, energy-dispersive x-ray spectroscopy, x-ray diffraction and 3D-surface analyzer. The mechanical properties (hardness, residual stresses and wear) were investigated by nanoindentation, interferometry and micro-tribometry (fretting-wear tests). Observations suggest that multilayer coatings are composed mostly of nanocrystalline. The residual stresses level in the films has practically affected all the physicochemical and mechanical properties as well as the wear behavior. Consequently, it is demonstrated that the coating containing moderate stresses has a better wear behavior compared to the coating developed with higher residual stresses. The friction contact between coated samples and alumina balls shows also a large variety of wear mechanisms. In particular, the abrasive wear of the coatings was a combination of plastic deformation, fine microcracking and microspallation. The application of these multilayers will be wood machining of green wood.     

Ti-Cr-B-N coatings prepared by pulsed cathodic-arc evaporation of ceramic TiCrB target produced by SHS

The method of pulsed cathodic-arc evaporation of composite targets based on self-propagating high-temperature synthesis has been applied for the first time to prepare nanocomposite coatings in the Ti-Cr-B-N system. The influence of the deposition-process parameters on the coating structure and properties has been studied. Structural investigations have been carried out using X-ray diffraction analysis, transmission and scanning electron microscopy, glow-discharge optical-emission spectroscopy, and optical profilometry. The coating properties have been determined by nanoindentation and tribological tests. The results of the study show that the coatings mainly consist of highly dispersed fcc phase based on Ti(Cr)N in the form of crystallites 1–2 nm in size; in addition, amorphous BNx phase has been found to exist in the coatings. The coatings obtained under optimal conditions have the following parameters: hardness 20–24 GPa, friction coefficient ～0.6, and reduced wear about 2 × 10^?6 mm³ N^?1 m^?1.     

A comparative study of reactive direct current magnetron sputtered CrAlN and CrN coatings

Approximately 1.5 μm thick CrN and CrAlN coatings were deposited on silicon and mild steel substrates by reactive direct current (DC) magnetron sputtering. The structural and mechanical properties of the coatings were characterized using X-ray diffraction (XRD) and nanoindentation techniques, respectively. The bonding structure of the coatings was characterized by X-ray photoelectron spectroscopy (XPS). The surface morphology of the coatings was studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The XRD data showed that the CrN and CrAlN coatings exhibited B1 NaCl structure. Nanoindentation measurements showed that as-deposited CrN and CrAlN coatings exhibited a hardness of 18 and 33 GPa, respectively. Results of the surface analysis of the as-deposited coatings using SEM and AFM showed a more compact and dense microstructure for CrAlN coatings. The thermal stability of the coatings was studied by heating the coatings in air from 400 to 900 °C. The structural changes as a result of heating were studied using micro-Raman spectroscopy. The Raman data revealed that CrN coatings got oxidized at 600 °C, whereas in the case of CrAlN coatings, no detectable oxides were formed even at 800 °C. After annealing up to 700 °C, the CrN coatings displayed a hardness of only about 7.5 GPa as compared to CrAlN coatings, which exhibited hardness as high as 22.5 GPa. The potentiodynamic polarization measurements in 3.5% NaCl solution indicated that the CrAlN coatings exhibited superior corrosion resistance as compared to CrN coatings.     

TC4钛合金表面沉积CrSiN/SiN纳米多层膜在3.5%NaCl溶液中的腐蚀磨损性能

为了研究纳米多层膜的耐腐蚀性能以及腐蚀磨损机理,采用离子源辅助磁控溅射在TC4钛合金表面制备不同调制周期的CrSiN/SiN纳米多层膜。使用扫描电子显微电镜、能谱仪表征涂层的微观结构、腐蚀形貌以及元素分布;使用划痕仪、纳米压痕仪、维氏硬度计测量涂层的膜基结合力、硬度、弹性模量及断裂韧性,采用电化学工作站以及销盘磨损仪测量涂层耐腐蚀性和腐蚀磨损性。结果表明:调制周期为90 nm与360 nm时涂层耐腐蚀性能较好,腐蚀电流密度分别为1.31×10~(-8)A·cm~(-2)和1.20×10~(-8)A·cm~(-2)。此外,调制周期为45nm时,涂层硬度及弹性模量最大,分别为(22.5±0.6)GPa和(226.4±6.3)GPa,且腐蚀磨损率最低,为9.67×10~(-7)mm~3·N~(-1)·m~(-1)。多层膜结构显著改善了TC4钛合金的耐腐蚀及腐蚀磨损性能。     

亚微米WC添加对超音速火焰喷涂WC-Co涂层磨损性能影响

采用超音速火焰喷涂方法(HVOF)在304不锈钢基体表面制备WC和WC-12Co的复合涂层WC-Co,研究亚微米WC的添加对涂层相组成、显微硬度、耐磨性能和表面形貌的影响。利用X射线衍射、压痕法、往复式摩擦磨损实验和扫描电子显微镜(SEM)分别对涂层的相组成、显微硬度、磨损性能和表面形貌进行分析测试,并分析涂层的磨损过程和机制。结果表明,添加质量分数5%的亚微米WC颗粒显著提高了涂层的显微硬度(16.3%);增强了涂层的耐磨性,磨损率从6.09×10-7 mm3/Nm减小到5.15×10-7 mm3/Nm(减小13.8%);亚微米WC颗粒喷涂后在涂层中保持了WC相,并主要存在于WC-Co扁平粒子界面和孔隙。基于涂层中扁平粒子的结合特性与磨损失效特征,建立强化模型,分析亚微米WC颗粒对涂层扁平粒子界面的强化机制。     

NbMoWTa/Ag自润滑纳米多层膜的力学性能及摩擦学行为∗

为提高高熵合金薄膜 NbMoWTa 的耐磨减摩性能,采用磁控溅射技术在 Si 基体上制备具有不同调制波长的 NbMoWTa / Ag 纳米多层膜,利用 XRD、SEM 和 TEM 等对纳米多层膜进行表征,分析其硬度和摩擦学性能。 结果表明不同调制周期结构的纳米多层膜结晶性良好。 多层膜硬度随着单层膜厚度 (100~ 5 nm)的降低而增加(5. 62 ~ 8. 39 GPa),在单层膜厚度减小到 20 nm 时,其塑性变形机制由位错在界面处的堆积机制转变为位错穿越界面运动机制;在尺寸小于 10 nm 时,多层膜的硬度接近于高熵合金 NbMoWTa 单质膜 (10. 93 GPa),这可能由随着单层厚度的降低引起 NbMoWTa 膜与 Ag 膜之间界面由半共格向共格转变所引起。 同时,通过摩擦磨损试验获得纯 NbMoWTa 薄膜的摩擦因数为 0. 49,磨损率为 1. 75×10^-5 mm³N^-1m^-1 ;单层膜厚度为 5 nm 的多层膜的摩擦因数为 0. 23,磨损率为 2. 19×10^-5 mm³N^-1m^-1 。 在 NbMoWTa 中添加 50%的 Ag 制备而成的纳米多层膜有共格强化效应,保证了其高硬度高强度的同时,由多层设计实现了耐磨和自润滑的协同控制。     

Effects of TaN nanoparticles on microstructure,mechanical properties and tribological performance of PEEK coating prepared by electrophoretic deposition

In order to solve the friction, wear and lubrication problems of titanium, a series of TaN/ployether- ether-ketone (PEEK) coatings were developed by electrophoretic deposition, and the effects of TaN nanoparticles on the microstructure, mechanical properties and tribological performance of coatings were explored. Results manifest that the introduction of TaN nanoparticles into PEEK coatings could improve the deposition efficiency, enhance the resistant deform capacity, increase the hardness, elastic modulus and adhesive bonding strength. Compared with the pure PEEK coating, the friction coefficient of P-TN-3 was greatly reduced by 31.25%. The wear resistance of P-TN-3 was also improved in huge boost, and its specific wear rate was decreased from 9.42×10^-5 to 1.62×10^-5 mm³·N^-1·m^-1. The homogeneous composite TaN/PEEK coatings prepared by electrophoretic deposition were well-adhered to the titanium alloy substrate, TaN nanoparticles could improve the strength of PEEK coating, and provide wear-resistance protection for titanium alloys.     

TiC颗粒增强镍基合金复合涂层的摩擦学性能(英文)

运用等离子喷涂技术制备了TiC颗粒增强镍基合金复合涂层,分析了TiC颗粒增强镍基合金复合涂层的微观结构,研究了其摩擦磨损行为与机理。结果表明:TiC颗粒增强镍基合金复合涂层主要由γ-Ni,CrB,Cr7C3和TiC构成;复合涂层与基底材料间形成了厚度为9.4μm的过渡层,达到了冶金结合。当TiC颗粒含量为30%(体积分数)时,复合涂层的摩擦系数和磨损率均最低,即其摩擦系数为0.33,较纯镍基合金涂层降低了30%;其磨损率为0.3×10-3mm3/m,是纯镍基合金涂层的1/3。当载荷在6～10N的范围内时,复合涂层呈轻微磨损,其磨损机理主要为粘着磨损;当载荷达到12N时,复合涂层产生严重磨损,其磨损机制转变为硬质相的脱落和转移层的层脱剥落。     

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.