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首页> 外文期刊>Journal of Applied Physics >Mechanism of adaptability for the nano-structured TiAlCrSiYN-based hard physical vapor deposition coatings under extreme frictional conditions
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Mechanism of adaptability for the nano-structured TiAlCrSiYN-based hard physical vapor deposition coatings under extreme frictional conditions

机译：纳米结构的TiAlCrSiYN基硬质物理气相沉积涂层在极端摩擦条件下的适应性机理

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Recently, a family of hard mono- and multilayer TiAlCrSiYN-based coatings have been introduced that exhibit adaptive behavior under extreme tribological conditions (in particular during dry ultrahigh speed machining of hardened tool steels). The major feature of these coatings is the formation of the tribo-films on the friction surface which possess high protective ability under operating temperatures of 1000 °C and above. These tribo-films are generated as a result of a self-organization process during friction. But the mechanism how these films affect adaptability of the hard coating is still an open question. The major mechanism proposed in this paper is associated with a strong gradient of temperatures within the layer of nano-scaled tribo-films. This trend was outlined by the performed thermodynamic analysis of friction phenomena combined with the developing of a numerical model of heat transfer within cutting zone based on the finite element method. The results of the theoretical studies show that the major physical-chemical processes during cutting are mostly concentrated within a layer of the tribo-films. This nano-tribological phenomenon produces beneficial heat distribution at the chip/tool interface which controls the tool life and wear behavior.Results of x-ray photoelectron spectroscopy studies indicate enhanced formation of protective sapphire- and mullite-like tribo-films on the friction surface of the multilayer TiAlCrSiYN/TiAlCrN coating. Comprehensive investigations of the structure and phase transformation within the coating layer under operation have been performed, using high resolution transmission electron microscopy, synchrotron radiation technique: x-ray absorption near-edge structure and XRD methods.The data obtained show that the tribo-films efficiently perform their thermal barrier functions preventing heat to penetrate into the body of coated cutting tool. Due to this the surface damaging process as well as non-beneficial - hase transformation (formation of AlN hex phase) drastically diminishes within the layer of the adaptive coating. Micro-mechanical properties measurements performed at room and elevated temperatures show that the hardness of the multilayer TiAlCrSiYN/TiAlCrN coating appears stable to 500 °C and then drops a little at 600 °C but still remains high. It means that if the surface tribo-films can reduce actual temperature down to this level the coating underneath is able to efficiently withstand heavy loads under operation.
机译：最近，已经引入了一系列的硬质单层和多层TiAlCrSiYN基涂层，这些涂层在极端摩擦条件下（尤其是在硬化工具钢的干超高速加工中）表现出适应性。这些涂层的主要特点是在摩擦表面上形成了摩擦膜，这些摩擦膜在1000°C及更高的工作温度下具有很高的防护能力。这些摩擦膜是由于摩擦过程中的自组织过程而产生的。但是，这些薄膜如何影响硬涂层适应性的机制仍是一个悬而未决的问题。本文提出的主要机理与纳米级摩擦膜层内温度的强梯度有关。通过对摩擦现象进行热力学分析并结合基于有限元方法的切削区域内传热数值模型的开发，可以概括出这种趋势。理论研究的结果表明，切割过程中的主要物理化学过程主要集中在摩擦膜层内。这种纳米级的摩擦学现象在切屑/刀具界面处产生了有利的热量分布，从而控制了刀具的寿命和磨损行为。X射线光电子能谱研究的结果表明，在摩擦表面上形成了保护性蓝宝石和莫来石状摩擦膜TiAlCrSiYN / TiAlCrN多层涂层的涂层。使用高分辨率透射电子显微镜，同步辐射技术，X射线吸收近边缘结构和XRD方法对涂层在操作过程中的结构和相变进行了全面研究，获得的数据表明摩擦膜有效地执行其隔热功能，防止热量渗透到涂层刀具的主体中。由于这个原因，在自适应涂层的层内，表面破坏过程以及非有益的，快速的转变（AlN六方相的形成）大大减少了。在室温和升高的温度下进行的微机械性能测量表明，多层TiAlCrSiYN / TiAlCrN涂层的硬度在500°C时似乎稳定，然后在600°C时略有下降，但仍然很高。这意味着，如果表面摩擦膜可以将实际温度降低到该水平，则其下面的涂层能够有效承受运行中的重负荷。

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