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首页> 外文学位 >An investigation of the mechanical and physical issues of the adhesion of chemically vapor deposited (CVD) diamond coatings on cemented carbide cutting tool inserts (Cemented carbide tools, Chemical vapor deposition).
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An investigation of the mechanical and physical issues of the adhesion of chemically vapor deposited (CVD) diamond coatings on cemented carbide cutting tool inserts (Cemented carbide tools, Chemical vapor deposition).

机译：研究硬质合金切削刀具刀片（硬质合金刀具，化学气相沉积）上化学气相沉积（CVD）金刚石涂层的附着力的机械和物理问题。

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摘要

In this work, the role of physical and mechanical factors on the adhesion strength of chemically vapor deposited (CVD) diamond coatings on cemented carbide inserts was investigated. The changes that occurred in the substrate residual stress due to pretreatment was measured by x-ray diffraction. A drop in the stress values of the substrates was found to occur after chemical etching and annealing processes. It was shown that the initial compressive residual stress present in the substrate was always found to drop as a result of the CVD diamond deposition process as well.; A scraper testing fixture was designed to examine the adhesion strength of diamond coatings to cemented carbide substrates. The adhesion was found to be extremely poor when the surface of the substrate was mechanically polished or seeded with a layer of nano-crystalline sized diamond particles. Diamond coatings having a thickness higher than 12 μm immediately failed after completion of the CVD process. Glass blasting the substrate prior to CVD diamond deposition and HF etching improved the adhesion strength of the diamond coatings when tested by the use of a scrapper test. Qualitative results show that the diamond coatings deposited on the samples treated by glass blasting and HF-HNO3 etching did not flake off during the scraping action.; The thermal residual stress in CVD diamond-coated carbide inserts was computed using a three dimensional finite element model. The model revealed that large thermal stresses existed along the flank and rake regions of the cutting inserts. It was observed that the thickness of the diamond coating affected the magnitudes of the stress components. The use of the indentation method as a quantitative adhesion test was shown not to be useful. The normal stress at the interface resulting from the indentation method were highly compressive leading to brittle cohesive failure rather than interfacial failure. The superposition of the total residual stresses and the stresses resulting from indentation did not yield a desired high tensile normal stress at the interface necessary for quantitative adhesion evaluation.
机译：在这项工作中，研究了物理和机械因素对硬质合金刀片上化学气相沉积（CVD）金刚石涂层附着强度的影响。通过X射线衍射测量由于预处理导致的在基板残余应力中发生的变化。发现在化学蚀刻和退火工艺之后，基板的应力值下降。结果表明，由于CVD金刚石沉积工艺的存在，总是发现基材中存在的初始压缩残余应力也降低了。设计了刮板测试夹具，以检查金刚石涂层与硬质合金基材的粘合强度。当对衬底的表面进行机械抛光或用纳米晶尺寸的金刚石颗粒层播种时，发现粘合性极差。 CVD工艺完成后，厚度大于12μm的金刚石涂层立即失效。当通过刮板测试进行测试时，在CVD金刚石沉积和HF蚀刻之前对基体进行玻璃喷砂处理可以改善金刚石涂层的附着强度。定性结果表明，在玻璃表面喷砂和HF-HNO 3 蚀刻处理后的样品上沉积的金刚石涂层在刮削过程中没有剥落。使用三维有限元模型计算CVD金刚石涂层硬质合金刀片中的热残余应力。该模型表明，在切削刀片的侧面和前刀面区域存在较大的热应力。观察到金刚石涂层的厚度影响应力分量的大小。压痕法不能用作定量粘合试验。压痕法在界面处产生的法向应力是高度压缩的，从而导致脆性的内聚破坏而不是界面破坏。总残余应力和压痕产生的应力的叠加未在定量粘合评估所必需的界面上产生所需的高拉伸法向应力。

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