Structure and Tribological Performance of Nanostructured ZrO<Subscript>2</Subscript>-3 mol% Y<Subscript>2</Subscript>O<Subscript>3</Subscript> Coatings Deposited by Air Plasma Spraying

In this study, nanostructured ZrO₂-3 mol% Y₂O₃ coatings were deposited by air plasma spray using reconstituted feedstock. The coating structures were characterized by x-ray diffractometer, micro-Raman spectrometer, field emission scanning electron microscope, and transmission electron microscope. It is revealed that the as-sprayed coating is mainly composed of columnar grains with diameters <100 nm and demonstrates the better toughness, higher microhardness, and lower porosity. It consists only of nontransformable tetragonal ZrO₂ phase. The tribological performance of the coating was examined with a ball-on-disk apparatus under dry sliding conditions. The results show that the friction coefficient of as-sprayed coating was approximately one-fifth of the conventional zirconia coating and wear rate was lower one order of magnitude than the conventional zirconia coating. The dominant wear mechanism is abrasive wear. The improved wear resistance can be attributed to the increased mechanical properties of as-sprayed coating.     

Preparation and characterization of plasma sprayed Ni3Al-hBN composite coating

Ni₃Al-hBN composite powders were manufactured by spray drying technology, and then plasma sprayed to form the coatings. The influence of hBN addition amount on the flowability and apparent density of the composite powders, as well as the mechanical and tribological properties of the as-sprayed coatings was evaluated. The results indicate that the spherical powders with uniformly distributed compositions are successfully manufactured by spray drying technology. Both the flowability and apparent density of the Ni₃Al-hBN powders, as well as the bond strength and hardness of the composite coatings decrease with the increase of hBN content. Addition of hBN less than 10 wt.% reduces the friction coefficient and brittle fracture of the coatings, which is beneficial to improve the tribological properties of the Ni₃Al-hBN composite coatings. However, high hBN addition, damaging the bond in the coating, will deteriorate the wear resistance of the coating. The Ni₃Al-hBN composite coating containing 10%hBN shows the optimum properties combining strength and hardness with tribological properties.     

CrN/CrAlSiN涂层海水环境下的摩擦学性能

为提高海洋装备摩擦零部件的摩擦学性能,采用多弧离子镀技术在316L不锈钢上制备了CrN/CrAlSiN涂层。通过XRD、XPS表征涂层的物相及成分,SEM和TEM表征涂层的形貌和微观结构,并用纳米压痕仪测试其硬度,采用摩擦磨损试验机对涂层在大气和海水环境中的摩擦磨损性能进行测试。结果表明:CrN/CrAlSiN涂层的微观结构主要有CrN相、AlN相以及非晶态Si_3N_4包裹CrN、AlN相,(111)择优取向最为明显;基于微观结构与CrN过渡层的设计,CrAlSiN涂层硬度高达35.5 GPa;较之于316L基底,涂层致密的结构使其在海水环境下表现出更好的耐腐蚀性能;在大气和海水环境下,CrN/CrAlSiN涂层的摩擦因数及磨损率均明显降低,在海水环境下达到最优。     

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.     

Correlation of crystallization behavior and mechanical properties of thermal sprayed PEEK coating

An amorphous PEEK coating was prepared on an Al substrate by a flame spraying process. The amorphous coating was subjected to an annealing treatment under an annealing temperature from 180 to 300 °C and a holding time from 1 to 30 min. The cold crystallization behavior of the as-sprayed coating differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) measurements. The hardness and tribological behavior of the coatings were investigated. Both DSC and WAXD analysis revealed that the annealed coatings exhibited a semi-crystalline structure. Coexistence of double crystal entities in annealed coatings was deduced. The annealed coatings exhibit higher hardness, lower friction coefficient and wear rate. Both the annealing temperature and holding time can benefit the coating hardness. The annealing condition in the studied range has little influence on the tribological behavior of the coatings. The variances of the coating mechanical properties were correlated with the modifications of the coating structures induced by the annealing treatments.     

Laser remelting of plasma-sprayed yttria partially stabilized zirconia coatings

A plasma-sprayed 8 wt.% yttria partially stabilized zirconia coating doped with 3 wt.% SiO₂ was remelted by laser. The microstructure of the as-sprayed and laser-remelted coatings was characterized by scanning electron microscopy (SEM), electron probe microanalysis (EPMA), transmission electron microscopy (TEM), and x-ray diffraction (XRD). The effect of laser remelting on the hardness, wear resistance, and thermal shock resistance of the coatings was also studied. The laser-remelted coating consists of fine solidification grains without the presence of pores and cracks. The elements are uniformly distributed in the laser-remelted coating. Nontransformable tetragonal (t′) phase is predominant in the laser-remelted coating with a small amount of cubic phase. Laser remelting greatly enhanced the hardness, wear resistance, and thermal shock resistance of the coatings, and should find more applications.     

Low temperature deposition of tribological coatings

The results of microstructural and tribological studies performed on sputter-deposited coatings of ZrO₂·2OY₂O₃, TiB₂ and B-18wt.%Si are reported. In each case, deposition parameters were identified that offered good tribological properties while maintaining low deposition temperatures (below 400 °C) to avoid distortion and softening of previously heat-treated substrates. Zirconia deposits were prepared with a pronounced columnar microstructure that provided excellent thermal fatigue and wear resistance, making them candidates for heat engine applications. The TiB₂ coatings were the hardest coatings prepared. These provided good wear resistance on steel substrates. The B-Si coating displayed excellent wear resistance and good adherence to copper and aluminum alloys.     

A comparative study of microstructure,oxidation resistance,mechanical, and tribological properties of coatings in Mo–B–(N), Cr–B–(N) and Ti–B–(N) systems

M–B–(N) (M = Mo, Cr, Ti) coatings were obtained by the magnetron sputtering of MoB, CrB₂, TiB, and TiB₂ targets in argon and in gaseous mixtures of argon with nitrogen. The structure and composition of the coatings have been investigated using scanning electron microscopy, glow-discharge optical emission spectroscopy, and X-ray diffraction. The mechanical and tribological properties of the coatings have been determined by nanoindentation, scratch-testing, and ball-on-disk tribological tests. The experiments on estimating the oxidation resistance of coatings were carried out in a temperature range of 600–1000°С. A distinctive feature of TiB₂ coatings was their high hardness (61 GPa). The Cr–B–(N) coatings had high maximum oxidation resistance (900°С (CrB₂) and 1000°С (Cr–B–N)) and possessed high resistance to the diffusion of elements from the metallic substrate up to a temperature of 1000°С. The Mo–B–N coatings were significantly inferior to the Ti–B–(N) and Cr–B–(N) coatings in their mechanical properties and oxidation resistance, as well as had а tendency to oxidize in air atmosphere after long exposure at room temperature. All of the coatings with nitrogen possessed a low coefficient of friction (in a range of 0.3–0.5) and low relative wear ((0.8–1.2) × 10^–6 mm3 N^–1 m^–1.     

Mechanical properties of thermal barrier coatings after isothermal oxidation.: Depth sensing indentation analysis

Thermal barrier coatings (TBC) are extensively used to protect metallic components in applications where the operating conditions include aggressive environment at high temperatures. Isothermal oxidation degrades the performance of these coatings, so this work analyses the mechanical properties (Young's modulus, E, and hardness, H) of TBC and its evolution after thermal exposure in air. ZrO₂(Y₂O₃) top coat and NiCrAlY bond coating were air plasma sprayed onto an Inconel 600 Ni base alloy. The TBC were isothermally oxidized in air at 950 °C and 1050 °C for 72, 144 and 336 h. Depth sensing indentation tests were carried out on the ceramic coating to evaluate E and H in the as-sprayed materials and after isothermal oxidation. An approach based on multiple tests at different loads was used to determine size independent apparent E an H. These mechanical properties, measured perpendicular to the surface, clearly decreased after isothermal oxidation as a consequence of microcracking within the ceramic coating.     

Microstructure,Mechanical Properties,and Two-Body Abrasive Wear Behavior of Cold-Sprayed 20 vol.% Cubic BN-NiCrAl Nanocomposite Coating

20 vol.% cubic boron nitride (cBN) dispersoid reinforced NiCrAl matrix nanocomposite coating was prepared by cold spray using mechanically alloyed nanostructured composite powders. The as-sprayed nanocomposite coating was annealed at a temperature of 750 °C to enhance the inter-particle bonding. Microstructure of spray powders and coatings was characterized. Vickers microhardness of the coatings was measured. Two-body abrasive wear behavior of the coatings was examined on a pin-on-disk test. It was found that, in mechanically alloyed composite powders, nano-sized and submicro-sized cBN particles are uniformly distributed in nanocrystalline NiCrAl matrix. Dense coating was deposited by cold spray at a gas temperature of 650 °C with the same phases and grain size as those of the starting powder. Vickers hardness test yielded a hardness of 1063 HV for the as-sprayed 20 vol.% cBN-NiCrAl coating. After annealed at 750 °C for 5 h, unbonded inter-particle boundaries were partially healed and evident grain growth of nanocrystalline NiCrAl was avoided. Wear resistance of the as-sprayed 20 vol.% cBN-NiCrAl nanocomposite coating was comparable to the HVOF-sprayed WC-12Co coating. Annealing of the nanocomposite coating resulted in the improvement of wear resistance by a factor of ~33% owing to the enhanced inter-particle bonding. Main material removal mechanisms during the abrasive wear are also discussed.     

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.     

不同双层结构AlCrN/AlCrVN多层涂层的力学和磨损性能

采用电弧离子镀的方法制备了不同数目（1、2、4、6）双层结构的AlCrN/AlCrVN多层涂层,并研究了多层结构对涂层微观结构、力学、摩擦学和切削性能的影响。结果显示,沉积态AlCrN/AlCrVN多层涂层主要由固溶(Al,Cr)N组成,优先生长方向为[111]晶向。与其他多层涂层相比,具有6层双层结构的AlCrN/AlCrVN涂层在高温下表现出较低的摩擦系数（约0.46）和磨损率（0.15×10^-11 m³/N·m）,以及较高的硬度（HK_0.05=38 000 MPa）和膜-基结合强度（L_C2=53±1 N）。多层涂层相邻层之间形成了较多的界面,有助于提高多层涂层的硬度和耐磨性。切削试验结果显示,当切削磨损标准VB=0.2时,AlCrN/AlCrVN-6涂层具有较高的硬度和耐磨性,最长的切削长度为7.4 m。     

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.     

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.     

Effect of Thermal Annealing on Tribological and Corrosion Properties of DLC Coatings

In this study, the mechanical, tribological, and corrosion properties of annealed diamond-like carbon (DLC) coatings on M2 steel with various annealing temperatures were investigated. The results indicated that DLC coating on M2 steel annealed at 500 °C had the worst performance. Both corrosion polarization resistance and wear resistance against ceramic alumina counterface of DLC coatings decreased with increasing annealing temperature, which can be due to the decline of the coating hardness after the thermal treatment. When sliding against aluminum counterface material, the DLC annealed at 600 °C had the lowest coefficient of friction (cof) and wear resistance due to its high graphitic structure and low hardness. Compared with the original coating, cofs increased for coatings treated at below 300 °C; however, further increasing the annealing temperature led to the decrease of the cofs. Little material attachment occurred between DLC coatings (original and annealed) and counterface materials (both alumina and aluminum balls) except for the DLC annealed at 600 °C, in which coating material transferred to the surface of counterface ball.     

Influence of deposition temperature on mechanical properties of plasma-sprayed hydroxyapatite coating on titanium alloy with ZrO<Subscript>2</Subscript> intermediate layer

Hydroxyapatite coatings were plasma sprayed on the Ti6A14V substrate with and without an intermediate ZrO₂ layer; meanwhile the temperatures of substrates were varied at 90, 140, and 200 °C. The coatings were subjected to the standard adhesion test per ASTM C633-79. The purpose of the investigation was to study the effects of those processing variables on the bonding strength and failure behavior of the system. It is found that the bonding strengths of HA/ZrO₂ and HA coatings generally decrease with increasing substrate temperature, except for the HA/ZrO₂ coating deposited at 200 °C. The rationale of the results is attributed to the residual stress reported in the literature. Introducing ZrO₂ bond coat is found to significantly promote the bonding strength of HA coating. The possible strengthening mechanism is the rougher surface of ZrO₂ bond coat and the higher toughness of ZrO₂, which provide the mechanical strengthening effects. The slightly denser HA in 200 °C deposited HA coating cannot explain the high bonding strength of the HA/ZrO₂ coating, nor the mechanical strengthening effect of ZrO₂ intermediate layer should apply. It is believed that a stronger diffusion bonding is formed at the interface of HA and ZrO₂, which increases the bonding between them chemically. The bonding strengths of HA/ZrO₂ and HA coatings are correlated with the area fraction of adhesive failure of the coatings. The correlation explains the findings in this study.     

多弧离子镀制备TiSiN-Cu涂层的结构和摩擦学性能

目的通过在TiSiN涂层中掺杂软金属Cu,提高TiSiN涂层的摩擦性能。方法采用多弧离子镀技术,在316L不锈钢基体上沉积TiSiN-Cu涂层。用扫描电子显微镜(SEM)观察涂层的表面形貌,用X射线光电子能谱仪(XPS)和X射线衍射仪(XRD)来分析涂层的元素组成和相组成,通过纳米压痕硬度测试和摩擦磨损实验,表征不同Cu含量TiSiN-Cu涂层的力学性能和摩擦学性能。结果 Cu含量对TiSiN涂层的结构、硬度和摩擦性能有明显影响。Cu在涂层中主要以单质形式存在,由于与空气接触,涂层表面有少量的CuO。随着Cu含量的增加,TiN的晶粒尺寸先减小后增加,硬度先升高后降低。在Cu原子数分数为6.28%时,硬度达到最大值29.26 GPa。在干摩擦条件下,TiSiN-Cu涂层的磨损率在Cu原子数分数为12.93%时达到最低,为6.65×10-7 mm~3/(N·m)。在海水环境下,涂层的磨损率较大。结论软金属Cu作为固体润滑颗粒可以明显改善Ti Si N涂层的干摩擦性能,在海水条件下,摩擦与腐蚀的交互作用加速了涂层材料的损耗。     

Tribological properties of plasma sprayed zircon-alumina powder mixture with and without laser re-melting

ABSTRACT

This investigation focusses on the wear mechanism of as-sprayed and laser treated mullite based coatings, produced by plasma spraying, under sliding wear condition. First, an alumina powder and zircon sand mixture was plasma sprayed to produce a mullite coating. Selected as-sprayed coatings were subsequently laser treated. The tribological performances of both as-sprayed and laser re-melted coatings were assessed using a pin-on-disc wear apparatus. Hardened steel and WC-Co balls served as rubbing counterparts. A plasma sprayed alumina coating was used for bench marking purposes. Plastic deformation was the dominant wear mechanism under low load-low speed condition for both as-sprayed and laser treated coatings. However, at higher loads and speeds the coatings were found to undergo micro-fracture followed by pulverisation. Wear resistance of the coatings improved following laser treatment.     

大气等离子喷涂TiB2-316L不锈钢基复合涂层及其耐磨性能

分别采用高能球磨制备了TiB2含量(质量分数)为10%的316L不锈钢基复合粉,高能球磨与喷雾干燥造粒工艺制备了TiB2含量(质量分数)为40%的316L不锈钢基复合粉,大气等离子喷涂制备相应的TiB2-316L不锈钢基金属陶瓷涂层与316L不锈钢涂层.室温下采用高速环块磨损试验研究TiB2-316L不锈钢基金属陶瓷涂层的磨损特性.采用X射线衍射分析涂层物相,扫描电镜分析喷涂粉末、涂层结构和摩擦副磨损表面形貌.结果表明,大气等离子喷涂两种制粉工艺获得的316L不锈钢基TiB2复合粉能获得较耐磨的316L不锈钢基TiB2复合涂层,耐磨性高于316L不锈钢涂层,且TiB2在复合涂层中增强涂层耐磨性的原因是TiB2颗粒在涂层316L韧性基体中充当强化相,且TiB2在摩擦接触处摩擦氧化形成的氧化产物具有自润滑特性,能减少涂层的磨损量.     

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。