Structural investigation of nanocrystalline diamond/amorphous carbon composite films

Nanocrystalline diamond/amorphous carbon (NCD/a-C) composite films have been prepared by microwave plasma chemical vapor deposition (MWCVD) from methane/nitrogen mixtures. The complex nature of the coatings required the application of a variety of complementary analytical techniques in order to elucidate their structure. The crystallinity of the samples was studied by selected-area electron diffraction (SAED). The diffraction patterns revealed the presence of diamond crystallites within the films. From the images taken by transmission electron microscopy (TEM) the crystallite size was determined to be on the order of 3–5 nm. The results were confirmed by X-ray diffraction (XRD) measurements exhibiting broad (111) and (220) peaks of diamond from which the average size of the crystallites was calculated. The grain boundary width is 1–1.5 nm as observed by TEM images which corresponds to a matrix volume fraction of about 40–50%. This correlates very well with the crystalline phase content of about 50% in the films estimated from their density (2.75 g/cm³ as determined by X-ray reflectivity). The bonding structure of the composite films was studied by electron energy loss spectroscopy (EELS) in the region of carbon core level. The spectra were dominated by a peak at 292 eV indicating the diamond nature of the investigated films. In addition, the spectra of NCD/a-C films possessed a shoulder at 284 eV due to the presence of a small sp² bonded fraction. This phase was identified also by X-ray photoelectron spectroscopy (XPS). The sp²/sp³ ratio was on the order of 10% as determined by deconvolution of the C1s XPS peak.     

PDC刀具切削参数对切削力和表面粗糙度的影响

研究了PDC刀具的切削参数对切削力和表面粗糙度的影响。结果表明进给量和背吃刀量是影响切削力的主要因素,切削速度对切削力的影响较小。小进给量、高切削速度有助于提高工件表面光洁度。     

热丝CVD法制备大面积金刚石薄膜基片的变形

采用热丝CVD法制备的大面积金刚石薄膜存在基片变形严重的问题,通过对热丝CVD设备和沉积工艺进行改进,成功解决了直径76mm、厚度0.4mm硅片的变形问题。结果表明:改进后金刚石薄膜基片的翘曲度为0.296%,比改进前的降低了88.9%;改进后金刚石薄膜的质量及晶粒大小均匀,膜厚不均匀度仅为1.53%,具有优异的大面积均匀性。     

陶瓷结合剂金刚石砂轮磨削超细晶粒硬质合金的表面粗糙度研究

本文结合单因素实验和正交实验,研究了从低速到高速磨削条件下,砂轮速度、进给速度、磨削深度、最大未变形磨削厚度以及磨削方式(顺磨或逆磨)对陶瓷结合剂金刚石砂轮磨削超细晶粒硬质合金表面粗糙度的影响规律,分析了影响超细晶粒硬质合金表面加工质量的原因。研究表明,总体来说磨削参数的变化对超细晶粒硬质合金表面粗糙度的影响程度不大。高速磨削时的表面粗糙度相比低速磨削得到了比较明显改善。逆磨时的粗糙度比顺磨大,随砂轮速度增加下降更快。相比传统硬质合金,磨削WC颗粒更细、强度更高的超细晶粒硬质合金的表面粗糙度更低。磨削参数对表面粗糙度的影响程度从小到大依次是磨削深度、砂轮速度和进给速度,实际加工时为同时获得较高的磨除率和表面质量,宜采用高砂轮速度、低进给和大切深的磨削组合。     

Thermal Diffusivity Measurement of Diamond Films1

This paper discusses the short-pulse-flash method developed for thermal diffusivity measurements on thin films. Two kinds of CVD diamond film have been prepared, and their thermal diffusivity in the perpendicular direction has been measured with this method. The measurement errors caused by the surface coating are discussed.     

Cr与金刚石界面碳化物形成机理研究

选用含Cr活性钎料,适当控制钎焊工艺,实现了金刚石与基体的高强度连接。采用扫描电子显微镜（SEM）和能谱仪（EDS）及X射线衍射结构（XRD）分析了真空加热条件下,含铬活性钎料与金刚石之间的界面反应以及界面反应产物,探讨了钎料与金刚石界面处碳化物的形成机理。分析结果表明,活性钎料中的Cr在金刚石表面富集并与金刚石中的C生成枝状的碳化物,既实现了化学冶金结合,生成的碳化物呈枝状,也进一步加强了对金刚石的把持作用。     

磨PCD刀具陶瓷结合剂金刚石砂轮的研究

本文研究制备Na2O-B203-Si02-Al203多元系基玻璃料,并配制成低温陶瓷结合剂,研究发现:耐火度为685℃,流动性为110%～130%,线膨胀系数为5.35×10-6℃-1的低温陶瓷结合剂具有优异的性能.制备的陶瓷结合剂金刚石砂轮在725℃烧成后,磨具的抗弯强度和洛氏硬度达到最佳值,分别58.61 MPa和77.9.用其磨削PCD刀片时锋利性好,磨削中间不需修整,砂轮耐用度高.运用扫描电子显微镜(SEM)分析了陶瓷结合剂金刚石磨具的断面形貌、磨削后磨削面形貌,表明结合剂对磨粒黏结牢固,断面组织均匀.     

磨粒预钎焊烧结金刚石雕刻磨头的性能研究

针对烧结金刚石雕刻磨头在加工过程中胎体容易产生裂纹甚至断裂等问题,采用预钎焊金刚石磨粒制作了金刚石雕刻磨头。利用有限元仿真方法分析不同金刚石磨粒界面结构对节块的力学性能的影响;通过三点抗弯实验测试节块的强度;并通过加工性能实验测试3种雕刻磨头的性能。结果表明:仿真实验中胎体上的应力能较多地转移到预钎焊磨粒上,从而降低了胎体自身的应力,提高了胎体的力学性能;预钎焊磨粒节块的抗弯强度也高于常规金刚石节块,在金刚石体积浓度为100%时,强度提高32.3%;预钎焊金刚石雕刻磨头的加工性能优于常规金刚石雕刻磨头。     

金刚石微粉复合镀膜的性能试验及其应用

对添加纳米级金刚石微粉的表面复合镀膜进行了性能试验和分析 ,结果表明 :镀层硬度达 10 0 0～115 0HV ,镀层晶粒致密 ,无方向性 ,抗剥落强度和耐磨性显著提高。金刚石微粉复合镀膜技术应用于实际生产可显著提高刀具和零件的使用寿命     

石材加工用金刚石带锯锯条的应力分析

针对金刚石带锯锯条在使用中易产生疲劳裂纹这一问题,较详细地分析和计算了锯条的受力状况及内应力状况,并应用有限元法对锯齿局部应力进行了计算,最后提出了防止产生疲劳裂纹的有关措施.