Developing an atmospheric aging evaluation model of acrylic coatings:A semi-supervised machine learning algorithm

To study the atmospheric aging of acrylic coatings,a two-year aging exposure experiment was conducted in 13 representative climatic environments in China.An atmospheric aging evaluation model of acrylic coatings was developed based on aging data including11 environmental factors from 567 cities.A hybrid method of random forest and Spearman correlation analysis was used to reduce the redundancy and multicollinearity of the data set by dimensionality reduction.A semi-supervised collaborative trained regression model was developed with the environmental factors as input and the low-frequency impedance modulus values of the electrochemical impedance spectra of acrylic coatings in 3.5wt%NaCl solution as output.The model improves accuracy compared to supervised learning algorithms model(support vector machines model).The model provides a new method for the rapid evaluation of the aging performance of acrylic coatings,and may also serve as a reference to evaluate the aging performance of other organic coatings.

Multilayered gradient CrN/ZrN coatings synthesized by magnetron sputtering

The multilayer gradient CrN/ZrN coatings were synthesized by a dual cathode DC magnetron sputtering.The influence of different species of reaction gases and partial pressures on structure and mechanical properties was investigated using XRD, AES, XPS, and nanoindentation. The results show that N2-NH3 mixture process gas is of benefit to the synthesis of superhard multilayered gradient CrN/ZrN coatings. The presence of the preferred orientations of CrN(111), (200) and ZrN (111), (220) in the structure is a main reason for superhardness of multilayered gradient coatings.

Microstructure and indentation toughness of Cr/CrN multilayer coatings by arc ion plating

Cr/CrN multilayer coatings with bilayer periods in the range from 1351 to 260 nm were prepared on 304 stainless steel substrates by arc ion plating to study the microstructure and properties of multilayer coatings and stimulate their application.SEM results confirm the clear periodicity of the Cr/CrN multilayer coatings and the clear interface between individual layers.XRD patterns reveal that these multilayer coatings contain Cr,CrN and Cr_2N phases.Because Cr layer is softer than its nitride layer,the hardness decreases with the shortening of the bilayer period(or increasing volume fraction of Cr layer).The Cr/CrN multilayer coating with 862 nm period possesses the highest indentation toughness due to a proper individual Cr and nitride layer thickness.However,for the Cr/CrN multilayer with the bilayer period of 1351 nm,it possesses the lowest toughness due to more nitride phase.The indentation toughness of Cr/CrN multilayer coatings is related with their bilayer period.A coating with a proper individual Cr and nitride layer thickness possesses the highest indentation toughness.

Mitigating the negative catalytic effect of CuO by FAS-17 coated Al nanopowder:Isothermal ageing of Al/CuO nanothermite at 71°C and 60%relative humidity

The safety and reliability of weapon systems would be significantly affected by changes in the performance of energetic materials due to ambient temperature and humidity.Nanothermites have promising applications due to their excellent reactivity.Therefore it becomes extremely important to understand their aging and failure process in the environment before using them.Here,the aging and failure process of Al/CuO in 71°C/60%RH were investigated,and showed that CuO nanoparticles negatively catalyze Al nanopowders,resulting in rapid hydration.The anti-aging effect of FAS-17-coated Al nanopowder was also examined.The aging process of Al,Al/CuO,and Al@FAS-17/CuO in high humidity and heat environment were revealed by quasi-in situ SEM and TEM methods.Compared with the aging of pure Al,the Al nanopowder in the nanothermites strongly agglomerated with the CuO nanopowder and hydrated earlier.This may be caused by CuO catalyzed hydration of Al nanopowder.The energy release experiments showed that the performance of Al/CuO decreased rapidly and failed to ignite after 4 h of aging.In contrast,the Al@FAS-17/CuO thermite can achieve long-term stability of up to 60 h in the same environment by simple cladding of FAS-17.It is found that FAS-17 coated Al nanopowder can prevent both particle agglomeration and water erosion,which is an effective means to make nanothermites application in high humidity and heat environment.

Tribological Behavior of Magnesium Alloy AZ91 Coated with TiN/CrN by Arc-glow Plasma Depositing

With advantages of high specific strength, low elastic module, good damping property et al., the magnesium alloys exhibit great potential applications in aerospace. But poor wear behavior results in limited use of magnesium alloy to static components. In this study, a 2 μm thick coating with 12 sub-layers of CrN and TiN is deposited alternately on the surface of magnesium alloy AZ91 by a novel method of arc-glow plasma depositing to improve its wear resistance. The composition and microstructure of the coating layer are analyzed by means of SEM, XRD and GDS. The friction coefficient is measured by ball on disc rubbing test, and the wear rates are also calculated. The results indicate that the friction coefficient is increased, but the wear rate is dropped sharply as compared with bare metal. The surface hardness is about HK0.01 1400.

Mechanical properties and friction-wear characteristics of VN/Ag multilayer coatings with heterogeneous and transition interfaces

The heterogeneous multilayer interface of VN/Ag coatings and transition multilayer interface of VN/Ag coatings were prepared on Inconel 781 and Si(100),and the microstructures,mechanical and tribological properties were investigated from 25 to 700℃.The results showed that the surface roughness and average grain size of VN/Ag coatings with transition multilayer interface are obviously larger than those of VN/Ag coatings with heterogeneous multilayer interface.The coatings with transition multilayer interface have higher adhesion force and hardness than the coatings with heterogeneous multilayer interface,and both coatings can effectively restrict the initiation and propagation of microcracks.Both coatings have excellent self-adaptive lubricating properties with a decrease of friction coefficient as the temperature increases,but their wear rates reveal a drastic increase.The phase composition of the worn area of both coatings was investigated,which indicates that a smooth Ag,Magnéli phase(V2O5)and bimetallic oxides(Ag3VO4 and AgVO3)can be responsible to the excellent lubricity of both coatings.To sum up,the coatings with transition multilayer interface have excellent adaptive lubricating properties and can properly control the diffusion rate and release rate of the lubricating phase,indicating that they have great potential in solving the problem of friction and wear of mechanical parts.

TiN/CrN multilayered hard coatings with TiCrN interlayer deposited by a filtered cathodic vacuum arc technique

TiN/CrN multilayered hard coatings with TiCrN interlayer were deposited onhigh speed steel substrates by using a filtered cathodic vacuum arc technique. The structure andcomposition of the coatings were characterized by scanning electron microscopy (SEM) and Augerelectron spectroscopy (AES). A high adhesion of up to 80 N was demonstrated by scratching tests forthe multi-layered coatings. Nanoindentation tests were performed to determine the hardness andelastic modulus of the coatings as a function of the multiplayer modulation period. It was observedthat the hardness of the multilayered coatings is higher than those of either TiN or CrN singlecoatings, and it increases with decreasing modulation periods, which is consistent with predictionsfrom the Hall-Petch type strengthening mechanism, though at small modulation periods, deviation fromthe Hall-Petch relation has been observed for the multilayered coatings. The life-span of drillscoated with TiN/CrN multilayered is triple as long as that coated with TiN layer.

Fracture Behavior of CrN Coatings Under Indentation and Dynamic Cycle Impact

Fracture behavior of CrN coatings deposited on the surface of silicon and AISI52100 steel by different energy ion beam assisted magnetron sputtering technique （IBAMS） was studied using indentation and dynamic cycle impact. It is found that, for the coatings on silicon substrate, the cracks form in the indentation corners and then propagate outward under Vickers indentation. The coating prepared using ion assisted energy of 800 eV shows the highest fracture resistance due to its compact structure. Under Rockwell indentation, only finer radial cracks are found in the CrN coating on AISI 52100 steel without ion assisting while in the condition of ion assisting energy of 800 eV, radial, lateral cracks and spalling appear in the vicinity of indentation. The fracture of CrN coatings under dynamic cycle impact is similar to fatigue. The impact fracture resistance of CrN coatings increases with the increase of ion assisting energy.

Effects of intermixing process on bonding strength of IBED CrN coatings

The coating substrate bonding strengths under different intermixing processes were evaluated by scratch and spherical rolling contact fatigue methods. The results show that for low bombarding energy of N ions dynamic recoiling at 10 keV and 20 keV, the coating layers are of excellent bonding strengths. The bonding strength of CrN coating with 40 keV static recoiling is higher than that of low energy(20 keV). On the other hand, the bonding strength of coating with 40 keV dynamic recoiling is much lower than that of static recoiling at the same energy and even less than that of dynamic recoiling intermixings at 10 keV and 20 keV energy. The results of scratch and spherical rolling contact fatigue methods exhibit the same trend for each group of recoiling methods, yet the results of the scratch and fatigue tests for two groups do not agree with each other.

The Study of Deposition Parameters, Properties for PVD Ti_xN and Cr_xN Coatings Using a Closed Field Unbalanced Magnetron Sputter Ion Plating System

Closed Field Unbalanced Magnetron Sputter Ion Plating (CFUBMSIP) systems have been used increasingly for PVD coating in recent years. TiN and CrN coatings, commonly used as the basic coating for a number of different hard coatings, have been chosen to study the coating process parameters for the CFUBMSIP system. In this paper, the process parameters, such as substrate temperature, substrate bias and OEM control, have been carefully examined to achieve hard and wear-resistance coatings with good adhesion. The coating structure and orientation were found to change according to the coating parameters. The Rockwell test and Scratch test were carried out to examine the coating adhesion; pin-on-disc testing was used to estimate the wear-resistant; micro-hardness was also used to determine coating hardness. HSS drill testing has been carried out to study the general properties of the coating for cutting tool application. A combination of process parameters can be selected to achieve good performance for the TiN and CrN coatings.

Ground-based investigation of atomic oxygen effects on naked Ag and Ag with protective organic coatings

Protective behavior of organic coatings of alkyd, epoxy, urethane and siloxane applied to silver solar cell interconnects and erosion of Ag were investigated by exposure experiments to ground simulation atomic oxygen (AO). Evaluations of their protective properties were made through assessing their mass change characteristics, chemical and physical changes to AO attack. The specimens after exposure were analyzed with SEM/EDAX and XPS. The results indicated that the silver is heavily etched, some coatings such as epoxy, alkyd, urethane are seriously degraded or removed as volatile oxides and the morphology of coatings changed. It is evident that siloxane coatings have excellent properties for anti-AO attack. The erosion product consists of silicon dioxide layer of compact texture and is left on the surface to provide adequate protection from further attack by the energetic AO.

不同掺Ag含量下高温(800℃)沉积CrN/Ag涂层的组织结构及其性能

为研究高温下掺入Ag的CrN涂层的组织性能,在沉积温度为800℃的条件下采用直流反应磁控溅射技术制备CrN/Ag硬质涂层。采用扫描电镜(SEM)、EDS能谱仪、X射线衍射(XRD)和维氏硬度计,综合分析了800℃沉积温度下,对不同Ag掺杂情况下CrN/Ag涂层的组织结构和性能特点,以及700℃热处理工艺对其的影响。结果表明,Ag添加导致CrN晶相生长由(200)择优取向向无择优取向转变,并使得CrN/Ag涂层表面粗糙化;少量Ag(7%(原子分数))添加可提高涂层硬度,过多Ag(21%(原子分数))添加明显降低涂层硬度;高温热处理(700℃/1h)后,纯CrN涂层的氧化并不明显,但是,随Ag含量增加,涂层氧化程度逐渐增加,且在高Ag(21%(原子分数))涂层中Ag溢出现象显著;涂层氧化及Ag溢出导致涂层硬度显著降低。

Ag含量对CrN/Ag薄膜微结构、力学及摩擦磨损性能的影响

通过反应磁控溅射法分别沉积了不同Ag含量(Ag/(Ag+Cr)=2.9~21.2%(原子比))的CrN/Ag复合膜,采用能谱仪、X射线衍射仪、纳米压痕仪、扫描电镜、摩擦磨损仪等研究了CrN/Ag复合膜的化学成份、微观结构、力学性能及摩擦磨损性能。结果表明:CrN/Ag薄膜为面心立方结构,由fcc-CrN及fcc-Ag构成。薄膜晶粒尺寸随Ag含量的升高逐渐降低。薄膜硬度随Ag含量的升高先升高后降低,当Ag含量为8.3%时,薄膜硬度最高,其最高值为23 GPa。薄膜硬度受细晶强化与软质Ag相的共同作用。CrN/Ag薄膜平均摩擦系数及磨损率随Ag含量的升高先降低后升高,当Ag含量为8.3%时,薄膜平均摩擦系数与磨损率最小,其最小值分别为0.50和0.68×10^(-8)mm^3。/N·mm。薄膜平均摩擦系数及磨损率主要受低剪切强度Ag含量和H/E值的影响。

Structure and mechanical properties of thick Cr/Cr_2N/CrN multilayer coating deposited by multi-arc ion plating

A Cr/Cr2N/CrN multilayer coating with a thickness of 24.4 μm was deposited by multi-arc ion plating. The coating was systematically characterized by field emission scanning electron microscopy(FESEM), X-ray photoelectron spectrometry(XPS), energy dispersive spectroscopy(EDS), X-ray diffraction(XRD) and transmission electron microscopy(TEM). Hardness and adhesion were tested by nanoindentation and scratch tester, respectively. The friction properties were investigated by a reciprocating UMT-3MT ball-on-disk tribometer in air and seawater. The results showed that the multilayer coating consisted of three different layers, with Cr,Cr2N and CrN phases, respectively. Compared with CrN single layer coating, the adhesion of the multilayer coating was improved significantly, the hardness of the multilayer coating was(21±2) GPa. The corrosion resistance of the multilayer coating was also improved in artificial seawater. The friction coefficient of multilayer coating was lower than that of CrN single layer coating both in air and seawater.

Si_3N_4/CrN_x/Ag/NiCrN_X/Si_3N_4复合涂层的光热性能

采用磁控溅射法在浮法玻璃上制备Si3N4/CrNx/Ag/NiCrNX/Si3N4复合涂层,并与浮法玻璃和传统Low-E玻璃进行对比研究了其光热性能。结果表明:随着Ag层厚度的增加,增加了红外线反射率,降低了可见光的透过率,具有良好的隔热性能;使用Si3N4作为内外保护层后,增加了复合涂层的硬度和附着力,而且不影响复合涂层的光谱特性。

CrN和CrN/Ag涂层的真空高温摩擦磨损性能

为改善涂层在真空、高温等苛刻条件下的摩擦学性能,利用中频直流磁控溅射技术在硅片和316L不锈钢上沉积了CrN和CrN/Ag涂层,利用扫描电镜、透射电镜和X射线衍射仪对涂层的成分及相结构进行了表征,通过划痕测试仪、纳米压痕仪和摩擦磨损试验机测试了涂层的力学及摩擦学性能。结果表明:添加Ag元素以后,CrN/Ag涂层硬度及承载能力有所减小,但结合强度增加;真空高温环境下CrN与CrN/Ag涂层摩擦因数随温度升高呈下降趋势,其中CrN涂层通过软化镀层减小剪切强度和阻力,从而减小摩擦因数,CrN/Ag涂层主要通过高温产生的热驱动力诱导表面Ag润滑膜的形成来减小摩擦因数;CrN涂层依靠自身剪切特性参与摩擦,而CrN/Ag涂层在真空高温下具有自润滑和持续润滑性能,作为自润滑零部件具有潜在的应用价值。

Mechanical and Tribological Properties of CrN Coated Inconel X750

Three CrN coatings were deposited on the Inconel X750 through the metal vapor vacuum arc ion implantation and the magnetic filtered cathodic vacuum arc deposition system(MEVVA-FCVA) with the N2 flow rates of 10,50,and 100sccm, respectively.The surface morphologies and cross-section morphologies of the CrN coatings were obtained through scanning electron microscopy(SEM) and an optical profilometer.The microstructures of the coatings were characterized through X-ray diffraction(XRD).The hardness and the elastic modulus of the coatings were tested by a nano-hardness tester.The adhesion strength and friction coefficients were investigated through scratch tests and ball-on-disk tests and the wear tracks were tested by the optical profilometer. The experimental results indicate that the CrN coating deposited on the Inconel X750 substrate displays a uniform thickness and a smooth surface. The mechanical properties behaves well as the N2 flow rate varies.The CrN coating significantly reduces the friction coefficient fluctuation and improves the antiadhesion and anti-wear properties of the Inconel X750.

Storage life prediction under pre-strained thermally-accelerated aging of HTPB coating using the change of crosslinking density

In order to predict the storage life of a certain type of HTPB(hydroyl-terminated polybutadiene)coating at 25℃ and analyze the influence of pre-strain on the storage life,the accelerated aging tests of HTPB coating at 40℃,50℃,60℃,70℃ with the pre-strain of 0%,3%,6%,9%,respectively were carried out.The variation regularity of the change of crosslinking density was analyzed and the aging model of HTPB coating under pre-strained thermally-accelerated aging was proposed.The storage life of HTPB coating at 25℃ was estimated by using the Berthelot equation as the end point of the aging life with a 30% decrease in maximum elongation.The results showed that the change of crosslinking density of HTPB coating increased with the increase of aging temperature and aging time,and decreased with the increase of pre-strain.Under 0% prestrain,the relationship between the change of crosslinking density of HTPB coating and the aging time can be described by the logarithmic model with the confidence probability greater than 99%.The stress relaxation phenomenon existed under 3%,6%and 9%pre-strained aging.The aging model considering chemical aging and pre-strain was established with the confidence probability greater than 90%.The storage life of HTPB coating was 15.2935 years at 25C under 0% prestrain,which was reduced by 13.9007%,75.6949% and 89.7859% under 3%,6% and 9% pre-strain,respectively.The existence of pre-strain has a serious impact on the storage life of HTPB coating,therefore,the pre-strain should be avoided as much as possible during the actual storage.

CrN/TiAlN多层涂层的微观结构和摩擦磨损性能

特种装备车辆往往在高速、高冲击等复杂环境下运行,底盘选装密封件表面容易被磨损造成密封失效,在密封工作面制备硬质涂层是提高服役寿命、延长维修周期的重要方法。采用物理气相沉积法在45#钢表面制备单层CrN涂层和不同过渡层厚度的多层CrN/TiAlN涂层,用X射线衍射仪、扫描电子显微镜、表面轮廓仪、纳米压痕仪和往复式摩擦磨损试验机,研究涂层的微观结构、机械性能和摩擦磨损性能。结果表明单层CrN涂层厚度为0.87μm,其硬度和模量最小为19.49 GPa和160.53 GPa。CrN/TiAlN多层涂层的硬度和模量明显提高,且随过渡层厚度增加而增大,4CrN/TiAlN涂层的硬度和模量可达到39.86 GPa和386.72 GPa。在空气环境下的摩擦磨损试验中,单层CrN涂层被快速破坏;CrN/TiAlN多层涂层的平均摩擦因数随着过渡层厚度的增加先增大后减小,最大磨损深度和磨痕截面积不断下降。4CrN/TiAlN涂层具有最优摩擦磨损性能,其平均摩擦因数为0.792 5,磨痕截面积为315.09μm^(2),磨损机理为磨粒磨损和少量粘着磨损。提高过渡层厚度能够降低基体的塑性变形,降低涂层与基体的物理性能差异,减少涂层开裂并提高涂层摩擦磨损性能。通过调控过渡层厚度获得性能优异的CrN/TiAlN多层涂层,研究成果可应用于车辆旋转密封件上,显著提高密封工作面耐磨损性能。

Si_3N_4-CrN_x-Ag-NiCrN_x-Si_3N_4复合涂层的光热特性

采用磁控溅射法在浮法玻璃基体上制备Si3N4-CrNx-Ag-NiCrNx-Si3N4复合玻璃涂层(简称:SAN Low-E玻璃),并与浮法玻璃和传统Low-E玻璃进行比较,研究了其光热特性。结果表明:SAN Low-E玻璃能反射大量红外线,降低可见光和紫外线的透过,具有良好的隔热性能;经过700℃热处理后,其光热特性和膜结构没有变化,优于浮法玻璃和传统的Low-E玻璃。