Multiscale Simulation of Microstructure Evolution during Preparation and Service Processes of Physical Vapor Deposited c-TiAlN Coatings

Physical Vapor Deposited(PVD)TiAlN coatings are extensively utilized as protective layers for cutting tools,renowned for their excellent comprehensive performance.To optimize quality control of TiAlN coatings for cutting tools,a multi-scale simulation approach is proposed that encompasses the microstructure evolution of coatings considering the entire preparation and service lifecycle of PVD TiAlN coatings.This scheme employs phase-field simulation to capture the essential microstructure of the PVD-prepared TiAlN coatings.Moreover,cutting simulation is used to determine the service temperature experienced during cutting processes at varying rates.Cahn-Hilliard modeling is finally utilized to consume the microstructure and service condition data to acquaint the microstructure evolution of TiAlN coatings throughout the cutting processes.This methodology effectively establishes a correlation between service temperature and its impact on the microstructure evolution of TiAlN coatings.It is expected that the present multi-scale numerical simulation approach will provide innovative strategies for assisting property design and lifespan prediction of TiAlN coatings.

Adhesion property of AlCrNbSiTi high-entropy alloy coating on zirconium:experimental and theoretical studies

Experimental scratch tests and first-principles calculations were used to investigate the adhesion property of AlCrNbSiTi high-entropy alloy(HEA)coatings on zirconium substrates.AlCrNbSiTi HEA and Cr coatings were deposited on Zr alloy substrates using multi-arc ion plating technology,and scratch tests were subsequently conducted to estimate the adhesion property of the coatings.The results indicated that Cr coatings had better adhesion strength than HEA coatings,and the HEA coatings showed brittleness.The special quasi-random structure approach was used to build HEA models,and Cr/Zr and HEA/Zr interface models were employed to investigate the cohesion between the coatings and Zr substrate using first-principles calculations.The calculated interface energies showed that the cohesion between the Cr coating and the Zr substrate was stronger than that of the HEA coating with Zr.In contrary to Al or Si in the HEA coating,Cr,Nb,and Ti atoms binded strongly with Zr substrate.Based on the calculated elastic constants,it was found that low Cr and high Al content decreased the mechanical performances of HEA coatings.Finally,this study demonstrated the utilization of a combined approach involving first-principles calculations and experimental studies for future HEA coating development.

First-principles study on the diffusion behavior of Cs and I in Cr coating

Cs and I can migrate through fuel-cladding interfaces and accelerate the cladding corrosion process induced by the fuel-cladding chemical interaction.Cr coating has emerged as an important candidate for mitigating this chemical interaction.In this study,first-principles calculations were employed to investigate the diffusion behavior of Cs and I in the Cr bulk and grain boundaries to reveal the microscopic interaction mitigation mechanisms at the fuel-cladding interface.The interaction between these two fission products and the Cr coating were studied systematically,and the Cs and I temperature-dependent diffusion coefficients in Cr were obtained using Bocquet’s oversized solute-atom model and Le Claire’s nine-frequency model,respectively.The results showed that the Cs and I migration barriers were significantly lower than that of Cr,and the Cs and I diffusion coefficients were more than three orders of magnitude larger than the Cr self-diffusion coefficient within the temperature range of Generation-IV fast reactors(below 1000 K),demonstrating the strong penetration ability of Cs and I.Furthermore,Cs and I are more likely to diffuse along the grain boundary because of the generally low migration barriers,indicating that the grain boundary serves as a fast diffusion channel for Cs and I.

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。

Microstructure and mechanical properties of TiN/TiAlN multilayer coatings deposited by arc ion plating with separate targets

TiN/TiAlN multilayer coatings were prepared by arc ion plating with separate targets. In order to decrease the unfavorable macroparticles, a straight magnetized filter was used for the low melting aluminium target. The results show that the output plasmas of titanium target without filter and aluminium target with filter reach the substrate with the same order of magnitude. Meanwhile, the number of macropartieles in TiN/TiAlN multilayer coatings deposited with separate targets is only 1/10-1/3 of that deposited with alloy target reported in literature. Al atom addition may lead to the decrease of peak at （200） lattice plane and strengthening of peak at （111） and （220） lattice planes. The measured hardness of TiN/TiAlN multilayer coatings accords with the mixture principle and the maximum hardness is HV2495. The adhesion strength reaches 75 N.

硬质合金表面预处理状态对TiAlCrSiN/TiAlN涂层结构与机械性能的影响

采用电弧离子镀工艺在不同预处理后的硬质合金表面制备TiAlCrSiN/TiAlN涂层,采用扫描电镜、X射线衍射仪、纳米压痕仪、压痕法等研究硬质合金表面形态和涂层结构、力学性能和结合强度。结果表明:抛光处理后的硬质合金表面十分平整,表面粗糙度低至7.7 nm。酸洗处理使硬质合金表层Co相溶解而暴露出更多的硬质相,表面粗糙度增大,TiAlCrSiN/TiAlN涂层在酸洗处理的硬质合金上生长速率增大,晶粒细小,硬度和弹性模量高,但硬模比较低。喷砂处理使Co相塑性变形而包络更多的硬质相,表面粗糙度大幅增加,TiAlCrSiN/TiAlN涂层在喷砂处理的硬质合金上生长速率稍降低,晶粒粗大,硬度和弹性模量小,但硬模比较高。酸洗+喷砂复合处理的硬质合金表面TiAlCrSiN/TiAlN涂层的硬度、弹性模量、硬模比介于两种单独处理方式的之间。

Microstructures and properties of PVD TiAlN coating deposited on cermets with different Ti(C,N)grain size

In the present work,TiAlN coatings were deposited on Ti(C,N)-based cermet substrates by physical vapor deposition method.Emphasis was focused on the influence of grain size of cermet substrates on the microstructure,growth behavior,mechanical properties,adhesion strength and wear behavior of the coatings.The results show that finer Ti(C,N)grain size leads to higher nucleation density and lower growth rate of coatings,indicating the crystallite size of the TiAlN coatings decreases with decreasing Ti(C,N)grain size.Nanoindentation tests show that the coatings deposited on cermets of the finest grain size exhibit the highest hardness(H),elastic modulus(E),H/E and H3/E2 of 34.5 GPa,433.2 GPa,0.080 and 0.22,respectively.The adhesion strength between coating and substrate is also enhanced with decreasing Ti(C,N)grain size by scratch test,which corresponds to the grain size and H/E and H3/E2 of the coating.Besides,the lower surface roughness and better mechanical properties of the coating deposited on finer grained cermet contribute to the better wear resistance of the coating.

Effect of cermet substrate characteristics on the microstructure and properties of TiAlN coatings

The composition and structure of substrate materials have important influences on coating performance,especially in terms of bond-ing strength and coating hardness,which determine whether the coating can be used for a given application.In this study,a TiAlN coating is deposited on Ti(C,N)-based cermet(TC)substrates with 0wt%-20wt%WC by arc ion plating.The influence of cermet substrate characterist-ics on the structure and properties of the TiAlN coating is then researched.Results show that the TiAlN coating deposited on the TC substrate has a columnar grain structure.As WC increases,the strength ratio of I(111)/I(200)and adhesive strength of TiAlN gradually increases.In the ab-sence of WC in the substrate,the preferred orientation of the TiAlN coating is(200).As WC increases,the preferred orientation of the TiAlN coating becomes(111)and(200).Notable differences in adhesive strength between the coating and substrate could be attributed to the micro-structure and composition of the latter.Scratching results show that the adhesive strengths of the TiAlN coating on the 0wt%-20wt%WC cer-met substrate are 52-65 N.Among the coatings obtained that on the TC substrate with 15wt%WC presents the highest H/E and H3/E2,which indicates that this coating also features the best wear resistance.The failure mechanisms of the coated tools include coating peeling,adhesive wear,and abrasive wear.As the cutting speed increases,the degree of flank wear increases and the durability of the coating decreases accord-ingly.Increases in WC result in an initial decrease followed by a gradual increase in the flank wear of the coated cermet inserts.

Effect of bias voltage on microstructure,mechanical and tribological properties of TiAlN coatings

TiAlN multilayer coatings composed of TiAl and TiAlN layers were deposited on ZL109 alloys using filtered cathodic vacuum arc(FCVA)technology.The effect of bias voltage on the microstructure and properties of the coating was systematically studied.The results show that the coating exhibits a multi-phase structure dominated by TiAlN phase.As the bias voltage increases,the orientation of TiAlN changes from(200)plane to(111)plane due to the increase of atomic mobility and lattice distortion.The hardness,elastic modulus and adhesion of the coating show the same trend of change,that is,first increase and then decrease.When the bias voltage is 75 V,the coating exhibits the highest hardness(~30.3 GPa),elastic modulus(~229.1 GPa),adhesion(HF 2)and the lowest wear rate(~4.44×10^(−5)mm^(3)/(N·m)).Compared with bare ZL109 alloy,the mechanical and tribological properties of TiAlN coated alloy surface can effectively be improved.

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.

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.

MICROSTRUCTURAL CHARACTERISTICSAND OXIDATION BEHAVIOR OFTi_(1-x)Al_xN PVD-COATINGS

Recent research on microstructural characteristics and oxidation behavior of Ti(1-x)AlxN thin film were surveyed. The Ti(1-x)AlxN coatings have three different phase regions, Bl structure for lower x value, wurtzite structure for higher x value and unidentified structure for medium x value. Based upon the selective oxidation mechanism the oxidation results of Ti(1-x)AlxN thin film with different Ti/Al ratio were predicated.

锆合金包壳Cr涂层界面元素扩散行为研究进展

随着核反应堆向高燃耗和更长服役寿命方向发展,对包壳材料的安全可靠性提出了更高的要求。锆合金表面Cr涂层由于其优异的抗高温氧化性能、耐腐蚀性能以及与基体良好的兼容性,被认为是最有前景的耐事故涂层包壳材料。综述了近年来涂层Cr与基体Zr界面元素扩散行为的研究成果,重点介绍了Cr涂层不同状态下的界面结构及演变规律,包括沉积、退火、辐照、氧化等状态。总结了Cr的扩散、分布和金属间化合物Zr-Cr-(Fe)层的生长动力学模型,归纳了界面扩散对涂层结构及性能的不利影响。扩散阻挡层是一种抑制涂层与基体互扩散的有效结构,介绍了阻挡层设计制备原则以及现有的和潜在的金属或陶瓷阻挡层材料,分析了2类典型阻挡层的优缺点。金属阻挡层能抑制Cr的扩散并延迟Cr-Zr共晶反应,但需要考虑中子经济性;虽然陶瓷阻挡层阻隔元素扩散的性能优异,但由于其与锆合金力学性能和热膨胀系数的差异明显,易产生微裂纹,需要考虑其抗裂性。最后提出了采用实验与分子动力学等相结合的多尺度研究方法开展界面研究,同时指出了目前研究工作中亟待解决的关键问题,这为后续的锆合金表面耐事故涂层研究与开发提供了重要参考。

低压冷喷涂制备Al-Ni-xCr复合涂层及其磨损特性研究

防腐性能较好的铝基涂层存在耐磨性不足的问题。本文设计了Ni粉和Cr粉复合沉积的方法来改善涂层的耐磨性。采用低压冷喷涂技术,制备了一系列Cr含量不同的Al-Ni-xCr复合涂层。通过金相、扫描电镜及X射线衍射等方法分析了复合涂层的微观形貌和成分。采用显微硬度计和磨损仪测试了涂层的显微硬度和磨损曲线,结合磨痕形貌分析了复合涂层的磨损机理。研究得出:低压冷喷涂可实现Al、Cr、Ni三种金属粉的共沉积,并获得致密、均匀的Al-Ni-xCr复合涂层。枝晶状Ni粉沉积率较高,Cr粉沉积率较低。含70 wt.%Cr的混粉涂层中,Cr含量约为31 wt.%。硬质颗粒Cr同时起到夯实涂层的作用,随着Cr含量增加,Al-Ni-xCr复合涂层的致密性提高。Al-Ni-xCr复合涂层的耐磨性能主要来自于Cr而非Ni,且与Cr含量有关。Al-Ni-70Cr复合涂层耐磨性最佳,磨损率仅为Al涂层的1/2。其优异的耐磨性归因于摩擦界面形成了稳定的、较硬的、含Cr量较高的复合氧化膜,抑制了磨损过程。

表面等离子渗氮对TiAlN涂层TiCN基金属陶瓷性能的影响

针对TiCN基金属陶瓷,调节不同N_(2)/Ar流量比对其进行等离子渗氮,并在渗氮样品表面沉积TiAlN涂层。采用GIXRD、EDS、SEM、HR-TEM、划痕测试、纳米压痕测试和光学图像测试仪等研究了渗氮过程N_(2)/Ar流量比对涂层组织结构、膜基界面状态、力学性能和涂层金属陶瓷刀片切削性能的影响。结果表明,随着N_(2)/Ar流量比的提高,TiAlN涂层晶粒逐渐细化,涂层厚度不断降低,基体表面仍有黏结相残留,进而影响表面涂层的生长和性能。当N_(2)/Ar流量比为1时,膜基界面处存在硬质相生长区和富黏结相生长区两种涂层生长区域,涂层在硬质相表面为共格外延生长,富黏结相区域存在原子排列紊乱的过渡区,涂层为半共格外延生长;涂层(200)晶面取向最强,织构系数为1.91;涂层硬模比(H/E)最高,为0.094。当N_(2)/Ar流量比为2时,TiAlN涂层的硬度和弹性模量均最高,分别为34.15GPa和416.64GPa。在切削加工过程中,切削接触区域主要发生磨粒磨损和粘着磨损。当N_(2)/Ar流量比为1时,涂层TiCN基金属陶瓷刀片切削性能最佳。

STUDY ON PTA CLAD (Cr,Fe)_7C_3/γ-Fe CERAMAL COMPOSITE COATING

A wear resistant （Cr, Fe）7C3/γ-Fe ceramalcomposite coating wasfabricatedon substrate of a 0.45% C carbon steel by plasma transferred arc （PTA） cladding process using the Fe-Cr-C elemental powder blends. The microstructure, microhardness and dry sliding wear resistance of the coating were evaluated. Results indicate that the plasma transferred arc clad ceramal composite coating has a rapidly solidified microstructure consisting of blocky primary （Cr, Fe）7C3 and the interblocky （ Cr, Fe）7C3/γ-Fe eutectics and is metallurgically bonded to the 0.45%C carbon steel substrate. The ceramal composite coating has high hardness and excellent wear resistance under dry sliding wear test condition.

Structure and wear resistance of TiN and TiAlN coatings on AZ91 alloy deposited by multi-arc ion plating

In order to investigate the microstructure of TiN and TiAlN coatings and their effect on the wear resistance of Mg alloy, TiN and TiAlN coatings were deposited on AZ91 magnesium alloy by multi-arc ion plating technology.TiN and Ti70Al30N coatings were prepared on the substrate,respectively,which exhibited dark golden color and compact microstructure.The microstructures of TiN and Ti70Al30N coatings were investigated by X-ray diffractometry(XRD)and scanning electron microscopy(SEM).The micro-hardness and wear resistance of TiN and Ti70Al30N coatings were investigated in comparison with the uncoated AZ91 alloy. The XRD peaks assigned to TiN and TiAlN phases are found.The hardness of TiN coatings is two times as high as that of AZ91 alloy, and Ti70Al30N coating exhibits the highest hardness.The wear resistance of the hard coatings increases obviously as result of their high hardness.

PTA clad (Cr,Fe)_7C_3/γ-Fe in situ ceramal composite coating

A wear-resistant （Cr, Fe）7C3/γ-Fe in situ ceramal composite coating was fabricated on the substrate of 0.45wt%C carbon steel by a plasma-transferred arc cladding process using the Fe-Cr-C elemental powder blends. The microstructure, microhardness, and dry-sliding wear resistance of the coating were evaluated. The results indicate that the microstructure of the coating, which was composed of （Cr, Fe）7C3 primary phase uniformly distributed in the γ-Fe, and the （Cr, Fe）7C3 eutectic matrix was metallurgically bonded to the 0.45wt%C carbon steel substrate. From substrate to coating, the microstructure of the coating exhibited an evident epitaxial growth character. The coating, indehiscent and tack-free, had high hardness and appropriate gradient. It had excellent wear resistance under the dry sliding wear test condition.

Cr涂层对Zr-4合金蠕变行为的影响

报道化学气相沉积Cr涂层对Zr-4合金蠕变性能的影响以及Cr涂层在服役温度下的热稳定性。利用扫描电镜、电子探针显微分析和电子背散射衍射研究样品的显微组织。结果表明:样品Zr-4基体中晶粒呈等轴状,存在明显的<0001>//ND织构。蠕变后涂层样品的Zr-4合金基体中亚晶界数量明显低于无涂层样品Zr-4合金基体中亚晶界数量,表明Cr涂层显著降低了Zr-4合金基体在蠕变过程中承载的应力,提高了合金的抗蠕变性能。Cr涂层在长时间扩散实验中保持高稳定性。涂层在高蠕变应力下(350℃时不小于157 MPa,400℃时不小于137 MPa)出现裂纹。系统总结蠕变断裂的数据,得到了关于稳态蠕变速率与蠕变断裂时间的Monkman-Grant关系式。

Effects of Cr interlayer on mechanical and tribological properties of Cr-Al-Si-N nanocomposite coating

Cr-A1-Si-N coatings were deposited on SUS 304 substrate by a hybrid coating system. A Cr interlayer was introduced between Cr-A1-Si-N coating and SUS 304 substrate to improve the coating adherence. The effects of Cr interlayer on the microhardness, adhesion, and tribological behavior of Cr-A1-Si-N coatings were systematically investigated. The results indicate that the microhardness of the Cr-A1-Si-N coatings gradually deceases with increasing thickness of Cr interlayers. The adhesion between Cr-A1-Si-N and SUS 304 substrate is improved by addition of the Cr interlayers. A peak critical load of-50 N is observed for the coating containing Cr interlayer of 60 nm as compared - 20 N for the coating without Cr interlayer. The thicker Cr interlayers result in reduced critical load values. Moreover, the wear resistance of the Cr-AI-Si-N coatings is greatly enhanced by introducing the Cr interlayer with thickness of 60 nm in spite of the decreased microhardness. The friction coefficient of the coating system is also moderately reduced.