CVD diamond coating for erosion protection at elevated temperatures

Small solid particles entrained in a gas-fluid turbomachinery flow can cause degradation of the component surfaces containing the flow by erosion and corrosion processes. As diamond is the hardest known material, much work has been done to use polycrystalline diamond (PCD) as a protective coating on parts operating in a hostile and abrasive environment. Little attention is given in the literature to the high-temperature erosion behavior of chemical vapor deposition (CVD) diamond on different substrates. The objectives of this research were to develop CVD diamond erosion barriers for surface protection of cemented tungsten carbide at high temperatures and to study the erosion behavior of the coatings. Microwave plasma chemical vapor deposition (MPCVD) was used to apply diamond films on WC-6%Co. The erosion behavior of the coated specimens was investigated experimentally by exposing them to abrasive particle-laden flow in a high-temperature wind tunnel. The obtained results show the effects of impingement angle, temperature, and particle dose on the erosion rate. The data demonstrate that uncoated substrates suffer 6–7 times higher wear compared to diamond-coated samples at elevated temperatures up to 538 °C when exposed to alumina particle flow. This study indicates that polycrystalline diamond is emerging as a promising erosion protective coating for high-temperature applications. Paper presented at Materials Solutions Conference & Exposition 2000, St. Louis, MO.     

镍改性层增强铜基底沉积金刚石膜的形核(英文)

在铜基底溅射约100nm厚的镍改性层,然后置入纳米金刚石悬浮液中超声震荡加载籽晶,随后在热丝化学气相沉积设备中制备出晶体颗粒接近热力学平衡形态的高质量金刚石膜,其中sp2碳相含量低于5.56%。分别采用激光拉曼光谱、扫描电镜与X射线衍射对金刚石膜的形核与生长进行研究。实验结果表明:在溅射有镍改性层的铜基底上,金刚石的形核密度比在无改性层的铜基底上的形核密度高10倍。镍改性层的增强机制主要来源于两个方面:镍改性层的纳米级粗糙表面增强金刚石籽晶颗粒的吸附;镍改性层的强催化效应加速铜基底上金刚石形核生长所需的石墨过渡层的形成,从而促进金刚石的快速形核。     

Surface characterization of (111) and (100) textured diamond coatings deposited to silicon

The use of diamond for infrared (IR) transmitting applications is of paramount importance to the defense industries. Diamond-coated IR transmitting materials are used on smart weapons and aircraft that use substrate materials such as silicon and germanium. In this investigation, diamond sheets were deposited using chemical vapor deposition. The as-grown diamond sheets were characterized for hydrogen content using detailed IR analysis. The deconvolution of the spectra in a three-phonon region (2700–3150 cm⁻¹) showed a number of vibration modes corresponding to the sp ^m CH _n phase of carbon. The spectra representing (100) and (111) textured diamond sheets, grown under different conditions, were compared. The (100) textured sheets contained two dominant peaks centered at 2860 and 2930 cm⁻¹, which correspond to the symmetric and asymmetric stretch bands of the CH₂ group. However, the sheet with (111) texture displayed multiple CH, CH₂, and CH₃ peaks on the spectrum. Using a standard sample called polymethyl methacrylate with known concentration, the hydrogen content associated with various modes was evaluated in the diamond sheets. IR active hydrogen in the chemical vapor deposited diamond sheets was also calculated by evaluating the area of the IR band. A discrepancy of one order of magnitude was found in the calculated and measured value. Using these measurements we suggest that the oscillator strength of the different IR modes varies depending upon the structure and H content of CVD diamond sheets.     

Hot-filament chemical vapor deposition of polycrystalline diamond coatings to interlayered steel

Zr-based nitride and carbide coatings have been deposited on high-speed steel by the cathodic arc method. Hot-filament chemical vapor deposition (CVD) has been used to deposit diamond films onto a treated steel surface. The films deposited by CVD were characterized using scanning electron microscopy, x-ray diffraction, and Raman spectroscopy to determine the surface morphology, roughness, crystal structure, and bonding characteristics. This paper was presented at the fourth International Surface Engineering Congress and Exposition held August 1–3, 2005 in St. Paul, MN.     

CVD金刚石厚膜刀具及应用研究

热丝CVD法沉积金刚石厚膜为全晶质纯多晶金刚石材料,是制造切削刀具的理想材料。本文针对国内外CVD金刚石厚膜焊接刀具研究与应用中存在的关键技术问题,结合我所近期相关技术研究进展,重点介绍了其制造工艺及关键技术。     

铜基体预沉积铜-金刚石复合过渡层金刚石膜的制备与表征（英文）

在铜基体表面电沉积铜-金刚石复合过渡层,采用电镀铜加固突出基体表面的金刚石颗粒,最后利用热丝化学气相沉积(HFCVD)法在复合过渡层上沉积大面积的与基体结合牢固的连续金刚石膜。采用扫描电子显微镜、拉曼光谱和压痕试验对所沉积的金刚石膜的表面形貌、内应力及膜/基结合性能进行研究。结果表明:金刚石膜由粗大的立方八面体颗粒与细小的(111)显露面颗粒组成,细颗粒填充在粗颗粒之间,形成连续的金刚石膜。复合过渡层中的露头金刚石经CVD同质外延生长成粗金刚石颗粒,而铜表面与粗金刚石之间的二面角上的二次形核繁衍长大成细金刚石颗粒。金刚石膜/基结合力的增强主要来源于金刚石膜与基体之间形成镶嵌咬合和较低的膜内应力。     

Influence of thermal exposure on the stability of metastable microstructures of sputter deposited nanocrystalline 304 and 310 stainless steel coatings

The effect of thermal exposure on the stability of the microstructures of magnetron sputter deposited 304 and 310 stainless steel (SS) coatings have been investigated. The coated 304SS samples were exposed to thermal cycling between 750 °C and room temperature and aged at 500 °C and 650 °C. X-ray diffraction (XRD) results revealed that the microstructures of the as-deposited 304SS and 310SS coatings consisted of αFe + σ and γFe + αFe, respectively. Thermal exposure at 500 °C and 650 °C resulted in the dissolution of σ and partial transformation of αFe into γFe in the 304SS coating and led to the precipitation of σ phase particles, at the expense of αFe, in the 310SS coating. The amount of σ phase in the 310SS coating increased with exposure time. However, both coatings showed no σ phase after thermal cycling to 750 °C for approximately 500 cycles.     

Effect of deposition temperature on properties of boron-doped diamond films on tungsten carbide substrate

Boron-doped diamond (BDD) films were deposited on the tungsten carbide substrates at different substrate temperatures ranging from 450 to 850 °C by hot filament chemical vapor deposition (HFCVD) method. The effect of deposition temperature on the properties of the boron-doped diamond films on tungsten carbide substrate was investigated. It is found that boron doping obviously enhances the growth rate of diamond films. A relatively high growth rate of 544 nm/h was obtained for the BDD film deposited on the tungsten carbide at 650 °C. The added boron-containing precursor gas apparently reduced activation energy of film growth to be 53.1 kJ/mol, thus accelerated the rate of deposition chemical reaction. Moreover, Raman and XRD analysis showed that heavy boron doping (750 and 850 °C) deteriorated the diamond crystallinity and produced a high defect density in the BDD films. Overall, 600–700 °C is found to be an optimum substrate temperature range for depositing BDD films on tungsten carbide substrate.     

金刚石表面镀钛及界面微结构的研究

本文研究了应用真空微蒸发镀方法实现了金刚石表面镀钛.X-射线衍射分析表明:镀钛层物相为TiC和Ti,反应形成的界面结构层次为:金刚石-TiC-Ti.TiC层一般厚度在几百到上千埃,镀Ti层总厚度大约150 nm-200 nm.根据金刚石、TiC和Ti的晶体结构特点,应用结构对应原则,创建了金刚石/TiC/Ti共格界面模型.金刚石和TiC之间的共格界面为:(111)金刚石∥(111)TiC,C原子的周期性对应关系为:6 ×0.252 nm≈5×0.304 nm,C原子错配率为0.526%;金刚石和TiC界面间的C原子形成垂直的键、偏斜的键和桥式三中心键.六方结构α-Ti的和面心立方的TiC之间的共格界面为:(1000)α-Ti∥(111)TiC,形成垂直键,Ti原子错配率为0.66%.     

甲烷体积分数对纳米金刚石薄膜形貌的影响

目的研究不同甲烷体积分数对纳米金刚石(NCD)薄膜生长的影响,实现较小晶粒尺寸、高平整度的NCD薄膜的制备。方法采用微波等离子体增强化学气相沉积的方法制备NCD薄膜,以CH4/H2为气源,在生长阶段控制其他条件不变的前提下,探讨不同甲烷体积分数对NCD晶粒尺寸、表面形貌以及表面粗糙度的影响。采用SEM、XRD等观测NCD薄膜的表面形貌和晶粒尺寸大小,并利用Raman对NCD薄膜的不同散射峰进行分析。结果随着甲烷体积分数的增加,薄膜晶粒尺寸有减小的趋势。甲烷体积分数较低时,晶形比较完整,但致密度较小;甲烷体积分数较高时,晶形杂乱无章,但致密度较好。当甲烷体积分数为9%时NCD薄膜平均粒径达到最小,为21.3 nm,表面粗糙度较好,但非晶金刚石成分开始大量生成,NCD薄膜质量开始变差;当甲烷体积分数为8%时其形貌最好,且此时最小表面粗糙度小于20 nm。通过Raman分析可知NCD薄膜中出现了硅峰和石墨烯特征峰。结论甲烷体积分数对NCD薄膜形貌有较大影响,甲烷体积分数为8%时是表面平整度由较差变好再逐渐变差的分界点,且平均晶粒尺寸为23.6 nm,薄膜表面具有较好的平整度。     

纳米金刚石薄膜的微结构和残余应力

采用双偏压热丝化学气相沉积法在不同栅极和衬底偏流下制备出纳米金刚石薄膜.采用Raman谱、SEM、AFM、纳米压痕法和XRD分析纳米金刚石膜的微结构、弹性模量和残余应力.分析结果表明,金刚石晶粒尺寸随着栅极和衬底偏流的增加而减小,而衬底偏流的加入会引起非金刚石成分的显著增加.金刚石晶界的畸变使得弹性模量随着栅极和衬底偏流的增加而减小,薄膜热应力也随之减小.晶界非金刚石成分引起金刚石本征应力呈压应力性质,晶界密度的增加使得本征应力随着栅极偏流的增加而增加,但衬底偏流引起薄膜抵抗变形能力剧烈下降,导致金刚石本征压应力的减小.     

活性成分对金刚石膜沉积速率和质量的影响

采用微波等离子体化学气相法合成的金刚石膜质量好,但采用常规CH4-H2气体体系,金刚石膜的沉积速率低.为此,实验研究了C2 H5OH-H2、CH4-H2-Ar和CH4-H2-N2等含有活性成分的体系下,微波功率、碳源浓度、气体压力对金刚石膜沉积速率、表面形貌、电阻率的影响.结果表明:使用含氧、氩、氮等活性成分的体系,金...     

Tribological properties of pulsed laser deposited Mo-S-Te composite films at moderate high temperatures

Tribological investigations of Mo-S-Te composite films were conducted on films grown at room temperature by pulsed laser deposition. The chemistry and microstructure of the films were characterized by X-ray diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy, and micro Raman spectroscopy. The films showed a granular morphology and a preferred basal plane growth of 2H-MoS₂ parallel to the substrate after annealing at high temperatures. The friction coefficients of the films were 0.05 at 300 °C and 0.10 at 450 °C for more than 10,000 cycles in air. Smeared hexagonal MoS₂ lubricant films were observed inside wear tracks while the tribochemical formation of wear debris occurred both inside and outside the wear tracks. The Te additives for increasing the film durability were proposed to slow oxidation of the lubricants at elevated temperatures by thermally-induced tellurium migration to the surface and the subsequent formation of the Te diffusion barrier. This mechanism could be significantly effective in high-temperature tribotests because of the increased tellurium mobility at high temperatures.     

低浓度氮气对MPCVD法制备金刚石膜的影响

利用微波等离子体化学气相沉积(MPCVD)法,在CH4/H2的混合反应气源中加入N2进行了金刚石膜的沉积实验,详细研究了N2浓度对金刚石膜生长的影响规律。使用扫描电子显微镜、激光拉曼光谱仪和X射线衍射仪等设备,表征了金刚石薄膜的表面形貌、相组成及晶面取向。实验结果表明:随着N2体积分数的增加(由0%增加到6%),薄膜中的非金刚石相含量逐渐增大,金刚石晶粒尺寸逐渐减小,晶面取向也由较大的晶面(111)转变成较小的晶面(100);当N2体积分数为4%时,沉积的金刚石膜表面为"菜花"状结构;低体积分数(2%)的N2有利于获得高度取向(100)的金刚石膜。     

The effects of substrate compositions on adhesion of diamond films deposited on Fe-base alloys

Diamond deposition on a series of ferrous alloy substrates has been examined in a microwave plasma enhanced chemical vapor deposition reactor. The results show that the nucleation, growth, and adhesion properties of the diamond are strongly dependent on the types and relative concentrations of the alloy elements in the substrates. Along with high nucleation densities, continuous and adherent diamond films have been successfully fabricated on the Al-modified alloy substrates, even in the absence of inter-layers or nucleation enhancing surface pre-treatment. The mechanism is preliminarily clarified regarding the delicate competition and balance between the base metal and the alloying elements in terms of their activation and deactivation ability on catalyzing graphite formation during deposition process.     

Influence of intermittently etching on quality of CVD diamond thin films

A new method, called growing-etching repetitional process based on hot filament chemical vapor deposition, was proposed to improve the quality of diamond film. During the deposition carbon source was intermittently closed letting hydrogen etch the surface of the diamond film fi＇om time to time. In order to find whether it is helpful to the films＇ quality, a series of experiments were done. The results show that the new method can enhance the orientation of the chemical vapor deposition diamond films, reduce the graphite phase and increase the film＇s surface resistivity.     

Formation of mullite coatings on silicon-based ceramics by chemical vapor deposition

Dense, uniform, mullite coatings have been deposited by chemical vapor deposition on SiC substrates, using a AlCl₃-SiCl₄-CO₂-H₂ system. The typical coating microstructure consisted of a thin layer of nanocrystallites of γ-Al₂O₃ in vitreous silica at the coating-substrate interface, with columnar mullite grains over this interfacial layer. The composition of the coating was graded such that the outer surface of the coating was highly alumina rich. The changes in the coating microstructure with processing parameters are discussed. The ability of mullite to incorporate such large composition variations is discussed in the light of vacancy formation as theAl/Si ratio is increased and the ordering of these vacancies leads to changes in lattice parameters. The formation of domains was studied by measuring the spacing of superlattice spots in electron diffraction patterns and the relationship between domain size andAl/Si ratio is discussed.     

正偏压对微波等离子体CVD法制备金刚石薄膜的影响

线形同轴耦合式微波等离子体CVD法是在硬质合金微型钻头(微钻)表面沉积金刚石涂层的最佳方法之一.本文首先研究了酸碱两步预处理后微钻表面的形貌和成分,然后研究了微钻工作表面金刚石的沉积情况,最后重点研究了正偏压对微钻不同位置金刚石生长的影响.结果表明,在微钻上施加50 V正偏压时,金刚石薄膜具有最佳的形貌和较好的均匀性.     

Deposition of tungsten-titanium carbides on surface of diamond by reactive PVD

1lNTR0DUCTl0NDiamondtoolsaremadegenerallybythepowdermetallurgicalprocess.Itisobviousthattheinterfaceenergybetweenthediamondandordinarymetalsoralloysisveryhigh,anddia-mondcrystalsareunwettabletoanylowmeltingpointmetalsandalloys,anditsabilityforweld-'[ljThe.t.di..[2~4]inmanycountriesingispoor.rhe.t.di..[2~4]inmanycountrieshaveshownthatsomecarbophilic(thatmeansaffinitytocarbon)metalsoralloysdepositedonthesurfaceofdiamondcanreactwithdiamondtoformmetal...bid..[5],whichhavestrongchem-istryaffini…