深振荡磁控溅射复合沉积CrN/TiN超晶格涂层的摩擦学性能

研究了IN718高温合金、WC-6%Co硬质合金和Si(100)基体上深振荡磁控溅射复合沉积CrN/TiN超晶格涂层的摩擦学性能。研究表明,涂层的生长对基体的类型没有选择性。随着基体硬度的升高,划痕结合力失效临界载荷增大,涂层结合力失效机制由翘曲失效转变为基体/涂层协同变形,未发现涂层的剥落失效。载荷为2N时,磨损机制由磨粒磨损和氧化磨损转变为轻微磨粒磨损。载荷为4 N时,IN 718基体上涂层的磨损机制为严重的氧化磨损,WC-6%Co基体上的涂层的磨损机制为磨粒磨损和氧化磨损,氧化物的产生、堆积和转移导致摩擦系数的波动。     

Tribological behavior of a TiSiCN coating tested in air and coolant

One TiSiCN coating and one TiN coating as a comparison basis were investigated in this paper. The coatings were deposited on stainless steel substrates using a Plasma Enhanced Magnetron Sputtering (PEMS) process, a variation of the physical vapour deposition (PVD) technique. The XRD pattern for the TiSiCN coating implied that the coating either consists of TiN and TiC phases or C be incorporated in TiN as a single solid solution. Both coatings exhibited good adhesion, although their thickness (17 μm-45 μm) was much larger than that of many commercial PVD coatings. The TiSiCN coating showed higher hardness than the TiN coating. The sliding tribological behavior of the coatings against alumimium and alumina counterparts was studied both in air and in a coolant (Hangsterfer's S-500) by pin-on-disc tests. Scanning electron microscopy (SEM) was used to examine the wear tracks on the discs and the wear scars on the pins. Compared to the TiN coating, the TiSiCN coating exhibited lower wear rates and lower coefficients of friction (C.O.F.) against those two kinds of counterparts when tested in air. The cutting coolant provided a lubricant effect and reduced the adhesive wear and C.O.F. between the coating and the counterpart.     

Tribological Behaviour and Cutting Performance of PVD-TiN Coating/Substrate System with Discontinuous Surface Architecture

TiN coating was deposited by arc evaporation PVD (physical vapor deposition) onto tool steel. A netted screen made of the stainless steel was placed between substrate and vaporizer in order to get discontinuous TiN coatings. Three kinds of surface condition (uncoated, continuous and discontinuous TiN coatings) were prepared and examined for their performance. Tribological behavior was investigated by means of dry and lubricated sliding tests at room temperature and 200 °C, on a disk-on-block and sphere-on-flat tribometer. The results show that the discontinuous TiN coating significantly decreases both the wear and the wearing speed of tool steel under sliding tests, and reduces friction under conditions of bidirectional sliding. In the three kinds of surface condition, the discontinuously coating has superiority for high speed cutting owing to its lifetime increasing compared with uncoated and continuously coated.     

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.     

Tribological behavior of TiN and CrN coatings sliding against an epoxy molding compound

TiN and CrN coatings were deposited by unbalanced magnetron sputtering, and then rubbed against an epoxy molding compound (EMC). In sliding against an EMC, TiN exhibited an extremely high wear rate and a low friction coefficient, while the CrN-coated sample showed the opposite behavior. To understand this difference, Raman spectroscopy and thermal testing were used to study both coatings. Combining the results of oxidation, Raman spectroscopy and tribological testing, it can be concluded that the oxidation and pore generation occurring in the TiN coating during sliding deteriorated the mechanical properties of the coating and therefore its wear resistance. The excellent wear performance of the CrN coating against EMC was related to its good oxidation resistance, and adhesion to the substrate at high temperature.     

TiN-Coating Effects on Stainless Steel Tribological Behavior Under Dry and Lubricated Conditions

The tribological properties of magnetron sputtered titanium nitride coating on 316L steel, sliding against Si₃N₄ ceramic ball under dry friction and synthetic perspiration lubrication, were investigated. The morphology of the worn surface and the elemental composition of the wear debris were examined by scanning electron microscopy and energy dispersive spectroscopy. TiN coatings and 316L stainless steel had better tribological properties under synthetic perspiration lubrication than under dry friction. Among the three tested materials (316L, 1.6 and 2.4 μm TiN coatings), 2.4 μm TiN coating exhibits the best wear resistance. The difference in wear damage of the three materials is essentially due to the wear mechanisms. For the TiN coating, the damage is attributed to abrasive wear under synthetic perspiration lubrication and the complex interactive mechanisms, including abrasive and adhesive wear, along with plastic deformation, under dry friction.     

Corrosion and tribological properties and impact fatigue behaviors of TiN- and DLC-coated stainless steels in a simulated body fluid environment

In this study, the corrosion and tribological properties of TiN and DLC coatings were investigated in a simulated body fluid (SBF) environment. The ball-on-plate impact tests were conducted on the coatings under a combined force of a 700 N static load and a 700 N dynamic impact load for 10,000 impacting cycles. The results indicated that the TiN and DLC coatings could achieve a higher corrosion polarization resistance and a more stable corrosion potential in the SBF environment than the uncoated stainless steel substrate SS316L. The good corrosion protection performance of TiN could be due to the formation of a Ti-O passive layer on the coating surface, which protected the coating from further corrosion. The superior corrosion property of the DLC coating was likely attributed to its chemical inertness under the SBF condition. The TiN and DLC coatings also exhibited an excellent wear resistance and chemical stability during the sliding tests against a high density polyethylene (HDPE) biomaterial. Compared to the DLC coating, the TiN coating has a better compatibility with the HDPE. However, the impact tests showed that the fatigue cracks and the coating chipping occurred on the TiN coating but not on the DLC coating.     

The Dry Sliding Wear Behavior of HVOF-Sprayed WC: Metal Composite Coatings

WC-based cermet coatings containing various metallic binders such as Ni, Co, and Cr are known for their superior tribological properties, particularly abrasion resistance and enhanced surface hardness. Consequently, these systems are considered as replacements for traditional hard chrome coatings in critical aircraft components such as landing gear. The purpose of this investigation was to conduct a comparative study on the dry sliding wear behavior of three WC-based cermet coatings (WC-12Ni, WC-20Cr₂C₃-7Ni, and WC-10Co-4Cr), when deposited on carbon steel substrates. Ball on disk wear tests were performed on the coatings using a CSEM Tribometer (pin-on-disk) with a 6-mm ruby ball at 20 N applied load, 0.2 m/s sliding velocity, and sliding distances up to 2000 m. Analysis of both the coating wear track and worn ruby ball was performed using optical microscopy and an Alphastep-250 profilometer. The results of the study revealed both wear of the ruby ball and coated disks allowed for a comparison of both the ball wear and coating wear for the systems considered. Generally, the use of Co and Cr as a binder significantly improved the sliding wear resistance of the coating compared to Ni and/or Cr₂C₃.     

Enhanced tribological properties of PECVD DLC coated thermally sprayed coatings

This research investigates the enhancement of the tribological properties of various thermally-sprayed coatings (APS Ni-50Cr, APS Al₂O₃-13%TiO₂ and HVOF WC-17Co) on steel substrate, achieved through the deposition of a thin DLC-based film. Higher adhesive strength between thin films and thermally-sprayed coatings compared to the simple thin film/carbon steel system was found by scratch testing. Dry sliding ball-on-disk tests performed under lower contact pressure conditions (5 N normal load, 6 mm diameter alumina ball) indicated a significant decrease in wear rates and friction coefficients of thermally-sprayed coatings when the thin DLC-based film is employed; little differences exist between the tribological behaviour of the various thin film/thermal spray coating systems and that of DLC-based film on carbon steel. Under higher contact pressure conditions (10 N normal load, 3 mm diameter alumina ball), the thin film/WC-Co system exhibited the best wear performance. These results indicate the superior tribological performance of DLC/thermal spray coating systems, especially under severe contact conditions.     

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.     

Improving tribological properties and machining performance of a-C coatings by doping with titanium

In this study, a-C:Ti _x% coatings with various levels of Ti addition are deposited on cemented tungsten carbide (WC-Co) substrates using a medium-frequency twin magnetron sputtering and unbalanced magnetron sputtering system. This study investigates the tribological properties of the coatings by conducting wear tests against an AISI 1045 steel counterbody under a cylinder-on-disk line contact wear mode using an oscillating friction and wear tester. Additionally, turning tests and high-speed through-hole drilling tests are performed on AISI 1045 steel counterbodies and PCB workpieces, respectively, to investigate the machining performance of coated turning cutters and microdrills. The a-C:Ti _x% coatings not only have improved tribological properties but also demonstrate enhanced machining performance. For sliding against the AISI 1045 steel counterbody under loads of 10 and 100 N, the results show that the optimal friction and wear resistance properties are provided by the a-C:Ti_13% and a-C:Ti_3% coatings, respectively. Meanwhile, the a-C:Ti_20% and a-C:Ti_51% coatings yield the optimal turning and drilling performance, respectively.     

超音速火焰喷涂WC-10Co4Cr涂层的耐滑动磨损行为

采用超音速火焰喷涂(HVOF)工艺制备微米结构WC-10Co4Cr涂层,分别采用金相显微镜、扫描电镜(SEM)、X射线衍射(XRD)和滑动磨损设备分析涂层的微观结构和滑动磨损行为。结果表明:采用液体煤油燃料HVOF喷涂的微米结构WC-10Co4Cr涂层的脱碳程度较低,涂层中仅出现WC和W2C相,而无η相(Co3W3C、Co6W6C)以及软相W。涂层微观结构致密,孔隙率约为1%,平均显微硬度为1 322HV0.3;在相同试验条件下,WC-10Co4Cr涂层的摩擦因数(约0.8)高于不锈钢(1Cr18Ni9Ti)的摩擦因数(约0.5),其滑动体积损失量仅为不锈钢涂层的1/146,具有优异的抗滑动磨损性能。涂层在滑动磨损过程中首先是粘结相的脱落,然后是WC颗粒的磨损。     

Evaluation offing surfaces with several coatings for friction, wear and scuffing life

Friction and wear of the sliding components in an automobile cause an increase in both fuel consumption and emission. Many engine components involved with sliding contact are all susceptible to scuffing failure at some points during their operating period. Therefore, it is important to evaluate the effects of various surface coatings on the tribological characteristics of the piston ring and cylinder block surface of a diesel engine. Wear and scuffing tests were conducted using a friction and wear measurement of the piston ring and cylinder block in a low friction diesel engine. The frictional forces, wear amounts and cycles to scuffing in the boundary lubricated sliding condition were measured using the reciprocating wear tester. The tester used a piece of the cylinder block as the reciprocating specimen and a segment of the piston ring material as the fixed pin. Several coatings on the ring specimen were used, such as DLC, TiN, Cr-ceramic and TiAlN, in order to improve the tribological characteristics of the ring. The coefficients of friction were monitored during the tests, and the wear volumes of the piston ring surfaces with various coatings were compared. Test results show that the DLC coating exhibits better tribological properties than the other coatings. The graphite structure of this coating is responsible for the low friction and wear of the DLC film. The TiN and DLC coatings show better scuffing resistance than the other coatings. The TiN and Cr-ceramic coated rings show good wear resistance and high friction.     

Tribological behaviour of HVOF sprayed near-nanostructured and microstructured WC-17wt.%Co coatings

A ‘duplex cobalt coated’ near-nanostructured WC-17wt.%Co powder was used to produce nanostructured coatings. The tribological performance of this coating was compared with a commercial WC-17wt.%Co microstructured coating using a pin-on-plate method (ASTM G133-05 standard) with a data acquisition software to perform a real time analysis of the sliding wear process. The wear rate was studied using loads from 10 to 60 N and for various sliding distances. The metallurgical analysis of the coatings showed that the duplex Co coated powder could be sprayed to produce dense coating. Furthermore, the near-nanostructured coating showed better fracture toughness values and this corresponded to a difference in wear mechanism between the two types of coatings. The greater “plasticity” in the near-nanostructured coating was recorded as microgrooves in the wear tracks and, in comparison, brittle fracture was observed in the wear tracks produced on the microstructured coating.     

Improvement of the wear resistance of Ti-based coating sliding against copper alloy

The multilayer coating, Ti10%-C:H/TiC/TiCN/TiN, was deposited on cemented tungsten carbide (WC-Co) substrate by an unbalanced magnetron sputtering system. Tribological characteristics of this coating were compared with the coatings of TiN, TiCN, and TiC/TiCN/TiN deposited on WC-Co substrates and the WC -Co substrate itself. The coating displayed excellent tribological properties, i.e., both low value and smooth curve of friction coefficient, and also, compared with the other tested materials, yielded the lowest wear depth when sliding against bronze under dry conditions. The coating thus protects against the high wear experienced when Ti-based coatings rub against copper alloy.     

Effects of Duplex Nitriding and TiN Coating Treatment on Wear Resistance,Corrosion Resistance and Biocompatibility of Ti6Al4V Alloy

Ti6Al4V alloy substrates were nitrided at 900 °C. TiN coatings were then deposited on the nitrided substrates using a closed-field unbalanced magnetron sputtering system. The microstructure, hardness and adhesion properties of the TiN-N-Ti6Al4V substrates were evaluated and compared with those of an untreated Ti6Al4V sample, a nitrided Ti6Al4V sample and a TiN-coated Ti6Al4V sample, respectively. The tribological properties of the various samples were investigated by means of reciprocating sliding wear tests performed in 0.9 wt.% NaCl solution against 316L, Si₃N₄ and Ti6Al4V balls, respectively. In addition, the corrosion resistance was evaluated using potentiodynamic polarization tests. Finally, the biocompatibility of the samples was investigated by observing the attachment and growth of purified mouse leukemic monocyte/macrophage cells (Raw 264.7) on the sample surface after culturing periods of 24, 72 and 120 h, respectively. Overall, the results showed that the duplex nitriding/TiN coating treatment significantly improved the tribological, anti-corrosion and biocompatibility properties of the original Ti6Al4V alloy.     

TiN及TiSiN涂层在海水环境下的摩擦学行为研究

目的对比研究海水环境下Ti N及Ti Si N涂层与Al2O3对磨的摩擦磨损行为。方法采用多弧离子镀技术在316L不锈钢及单晶硅片上制备Ti N及Ti Si N涂层。利用场发射扫描电子显微镜(SEM)、X射线衍射仪(XRD)及X射线光电子能谱仪(XPS)分析了涂层的截面形貌及化学组织成分。选择纳米压痕仪测量了Ti N及Ti Si N涂层的硬度及弹性模量,使用UMT-3往复式摩擦试验机研究了人工模拟海水环境下Al2O3与Ti N及Ti Si N涂层对磨后的摩擦磨损行为,并采用扫描电镜(SEM)、电子能谱(EDS)及表面轮廓仪来深入分析了磨痕的摩擦磨损情况。结果研究表明,Ti N涂层的硬度为32.5 GPa,当Si元素掺入涂层以后,Ti Si N涂层的硬度提高到了37 GPa。同时,较之于Ti N涂层,Ti Si N涂层的腐蚀电流密度下降了一个数量级。在摩擦实验中,Ti N涂层的摩擦系数和磨损率分别为0.35和5.21×10-6 mm3/(N·m),而Ti Si N涂层的摩擦系数和磨损率均有明显下降,分别为0.24和1.96×10-6 mm3/(N·m)。结论 Si元素掺杂后能显著提高Ti N涂层在海水环境下的摩擦学性能,主要归因于结构的致密,硬度、韧性、抗腐蚀性的提高及润滑相的形成。     

Hard and wear-resistant titanium nitride coatings for cemented carbide cutting tools by pulsed high energy density plasma

Hard and wear-resistant titanium nitride coatings were deposited by pulsed high energy density plasma technique on cemented carbide cutting tools at ambient temperature. The coating thickness was measured by an optical profiler and surface Auger microprobe. The elemental and phase compositions and distribution of the coatings were determined by Auger microprobe, x-photon electron spectroscope, and X-ray diffractometer. The microstructures of the coatings were observed by scanning electron microscope and the roughness of the sample surface was measured by an optical profiler. The mechanical properties of the coatings were determined by nanoindentation and nanoscratch tests. The tribological properties were evaluated by the cutting performances of the coated tools applied in turning hardened CrWMn steel under industrial conditions. The structural and mechanical properties of the coatings were found to depend strongly on deposition conditions. Under optimized deposition conditions, the adhesive strength of TiN film to the substrate was satisfactory with the highest critical load up to more than 90 mN. The TiN films possess very high values of nanohardness and Young’s modulus, which are near to 27 GPa and 450 GPa, respectively. The wear resistance and edge life of the cemented carbide tools were improved dramatically because of the deposition of titanium nitride coatings.     

Performance of low-friction coatings in helium environments

The aim of this research work was to investigate the possibility of replacing soft PTFE‐based coatings on components operating in helium atmosphere. Focus was on maintaining low friction and improving surface wear resistance. Therefore two commercial DLC coatings (a-C:H and Me-C:H), CrN coating and reference PTFE‐based Rulon and Xylan coatings were included in this investigation. Coatings were deposited on hardened 100Cr6‐bearing steel discs and tested against uncoated steel balls in pin-on-disc contact configuration under dry reciprocating and unidirectional sliding in helium atmosphere. Investigation was concentrated on the effect of running-in, contact pressure, sliding speed and counter-material type and surface treatment on the tribological behaviour of hydrogenated DLC coatings when running‐in in helium.     

Sliding wear evaluation of hot isostatically pressed thermal spray ceramet coatings

The principal aim of this study was to compare the sliding wear performance of as-sprayed and Hot Isostatically Pressed (HIPed) thermal spray cermet (WC-12Co) coatings. Results indicate that HIPing technique can be successfully applied to post-treat thermal spray cermet coatings for improved sliding wear performance, not only in terms of coating wear, but also in terms of the total volume loss for test couples. WC-12Co coatings sprayed by a HVOF system were deposited on SUJ-2 bearing steel substrate and then encapsulated and HIPed at 850 °C for one hour. A high frequency reciprocating ball on plate rig was used to measure the sliding wear resistance of these coatings in dry conditions under steel and ceramic contact configurations at two different loads. Results are discussed in terms of coating microstructure, microhardness, fracture toughness and residual stress evaluations. Microstructural investigations indicate fundamental changes in grain morphology, whereas x-ray diffraction revealed beneficial transformations in phase composition of these coatings during the HIPing post treatment. The effects of these microstructural changes on the physical properties and wear resistance are discussed.