硬质合金/金刚石薄膜的制备和附着性能的研究

【作者】 杨莉；

【导师】 余志明；

【作者基本信息】 中南大学 ， 材料学， 2004， 硕士

【摘要】 本研究采用热丝CVD法在YG3硬质合金(WC-3％Co)和YG6硬质合金(WC-6％Co)基体上沉积了金刚石薄膜。在对硬膜-软基体体系的附着机理进行综合分析的基础上，通过考察基体含Co量、基体预处理和CVD工艺(温度、浓度和压强等参数)对表面层去Co、金刚石薄膜形核和长大的影响，研究了改善膜／基附着性能的途径。得到如下结论： 1．硬质合金基体经一步或两步浸蚀法都能不同程度地去除基体表面的钻，抑制金刚石沉积过程中表面Co的不利影响。较之一步法，二步法处理的效果更明显。基体浸蚀层达10μm左右，有效地防止了金刚石沉积过程中钴的迁移和挥发，可以沉积出质量高、附着力好的金刚石薄膜。 2．二步浸蚀法采用浸蚀剂B腐蚀30min，再用浸蚀剂C浸泡30s最佳，YG6样品表面Co含量减少到0.82％，YG3样品降低到1.36％。基体上成核密度大，形成连续的金刚石薄膜，组织结构具有{110}面取向，薄膜附着性较好。 3．硬质合金基体上金刚石薄膜的附着性能主要与基体表面钴含量、基体表面特性、金刚石的形核密度以及金刚石膜的质量等因素有关。基体钴含量的降低对改善膜／基附着性能有利。采用相同的处理工艺，YG6系列比YG3系列钴含量下降的幅度大，薄膜晶形完整，膜／基结合效果更理想。 4．硬质合金基体上金刚石薄膜的沉积工艺对金刚石形核密度、薄膜形貌和结构以及膜／基界面上非金刚石相的含量有重要影响，从而影响薄膜与基体间的附着性能。在其它沉积条件相同的情况下，基体温度为750℃左右，沉积气压为20Torr，甲烷浓度为1％时，硬质合金基体上金刚石薄膜的晶粒大小、生长取向和附着性能较好。更多还原

【Abstract】 In the present work, diamond thin films were deposited on the cobalt-cemented tungsten carbide (WC-6%Co and WC-3%Co) by Hot Filament Chemical Vapor Deposition (HFCVD). After sythetically analysing the mechanism of adhesion on the system of hard film and soft substrate, an investigation had been made on the methods of improving the adhesion by studying the effects of Co content, surface etching treatment and process parameter in diamond nucleation and growth. Conclusion can be drawn as following:(1) One-step and Two-step chemical etching methods can remove the Co contents on the cemented carbides substrate and prevent Co negative effects in the process of deposition. Compared with one-step method, two-step etching is a more effective method for removing cobalt from WC-Co. This role can decrease the diffusion of Co to substrate surface and guarantee the deposition of good qualitative and adhesive diamond films.(2) Among two-step etching, firstly using etching reagent B to attack WC grain 30 minute and then with etching reagent C 30 second removing Co is the most effective way consequently. The Co content of surface area can be reduced to 0.82% and 1.36% for YG6 and YG3 sample, respectively. The nucleation density can increase remarkably, at the same time, the purity of diamond thin films can improve greatly. A slight preference towards {110} oriented texture can be observed by XRD analysis.(3) The adhesion between the diamond thin films and the cemented carbides substrates is dependent on the content of cobalt at the surface, the WC-Co substrate properties, the nucleation density and the quality of diamond films. Especially, the content of cobalt is a more important factor. The decreasing of Co content is easy for improving the adhesion between substrate and thin film. Of the two types of substrate used, WC-6%Co and WC-3%Co, it was easier to remove the Co from the former 6% samples.(4) The conditions of diamond film deposition evidently affect on the nucleation density, the morphology, the structure, the purity of diamond film and lastly its adhesion strength. Our experiments show that the adhesion between diamond thin films and cemented carbide substrates is strong when substrate temperature is 750, chamber pressure is 20Torr and methane concentration is 1%.更多还原