【作者】 黄碧龙；

【导师】 李戈扬；

【作者基本信息】 上海交通大学 ， 材料学， 2008， 硕士

【摘要】 以TiN为代表的硬质陶瓷薄膜作为刀具涂层取得了巨大的成功,有力地推动了制造业的发展。高速、干式切削等加工技术的进步对刀具涂层提出了更高的要求。纳米多层膜的高硬度以及能够通过材料组合获得其它优异性能的可裁剪性,使其成为一类具有广泛应用潜力的涂层材料。而其通过微结构的设计获得高硬度的强化机制更具理论研究价值。已有的研究表明,在很多多层膜中,一种调制层在一定条件下会使另一调制层发生相转变,如TiN/SiO2多层膜中,非晶层的SiO2在厚度低于约1nm时在立方TIN膜板层的作用下晶体化为与TiN结构相同的赝晶。但目前关于非晶晶化的研究主要集中在以立方氮化物为模板的纳米多层膜体系中,对于以其他晶体结构调制层为膜板层的多层膜体系的研究却鲜有报道。本文采用反应溅射方法制备了TiN/AlON纳米多层膜,采用化合物靶溅射制备了AlN/TiB₂纳米多层膜。研究了原为非晶态的AlON和TiB₂调制层在立方结构TiN和六方结构AlN晶体层“模板作用”下的晶化条件,以及非晶层晶化对纳米多层膜生长结构和力学性能的影响。论文还提出了一种测量金属基体上硬质薄膜内应力的应力释放测量法。研究结果表明:1.在采用氧化物Al2O3靶在Ar、N2混合气氛中通过反应溅射制备TiN/AlON纳米多层膜的过程中,溅射的Al2O3分子中的氧原子会部分被氮原子所取代,形成非晶态的AlON化合物。2.TiN/AlON纳米多层膜中,AlON在层厚小于0.6 nm时被强制晶化并与TiN形成共格外延生长结构,多层膜产生硬度升高的效应,最高硬度达40.6GPa;进一步增加其层厚,AlON向非晶态转变,从而破坏多层膜的晶体生长,多层膜的硬度随之降低。由于具有很高的沉积速率,这种采用反应溅射制备高硬度TiN/AlON纳米多层膜的技术有望用于工业生产。3.AlN/TiB₂纳米多层膜中,由于AlN的膜板作用,原为非晶态的TiB₂层在小厚度时被强制晶化,并与h-AlN形成共格外延生长结构。多层膜的硬度获得提高,最高达到30.5GPa。厚度继续增加,TiB₂转变为以非晶态生长,多层膜的共格外延生长结构受到破坏,相应地,其硬度也随之降低。4.论文基于Stoney公式,提出了一种通过电火花切割金属基片释放薄膜应力的内应力测量方法,该方法可准确地测量金属基体上硬质薄膜内应力,同时因可以直接从金属零件上取样而更方便。更多还原

【Abstract】 The application of hard ceramic thin films, such as TiN, as coatings of cutting tool have gained huge success and significantly promoted the development of manufacturing industry. The advancement of machining techniques, such as high speed, dry cutting, demands better properties for the coatings of cutting tools. The nano-multilayer makes itself a promising candidate coating for its high hardness and the diversity, from which various superior properties could be obtained. Meanwhile, of more theoretic value is its hardening mechanism, where high hardness is obtained by designing its microstructure.It is already known that in some multilayers, one modulation layer could be phase transformed and grow epitaxially with the other layer. In TiN/SiO2 mulitlayers, for example, when the thickness is less than 1nm, the amorphous SiO2 layer is transformed into the pseudo-crystal under the“template effects”of TiN modulation layer, which shares the structure with cubic TiN layer. However, current researches on crystallization of amorphous are mostly focused on the cubic nitride based nano-mulitlayers. Few, if any, investigations have been done on the multilayer series, whose template layers have different structures.A series of TiN/AlON nano-multilayers are synthesized with chemical sputtering method; a series of AlN/TiB2 nano-multilayers are synthesized with physical sputtering method. The crystallizing conditions are investigated, under which amorphous AlON and TiB2 modulation layers are crystallized for“the template effects”of cubic TiN and hexagonal AlN. The effects of the crystallization of amorphous layers on multilayers’microstructure and mechanical properties are also studied. A method of measuring internal stresses in the metal based hard thin films is proposed. Results are as follows:1. When using Al₂O₃ target to synthesize TiN/AlON multilayers in the gas mixture of Ar and N₂, the O atom in the Al₂O₃ will be partially replaced by N atom, forming amorphous AlON.2. When the thickness of AlON layer is less than 0.6nm, AlON is forced to crystallize and grow epitaxially with TiN and the hardness of multilayers are enhanced with the highest value reaching 40.6GPa. Further increasing the thickness, the AlON layer transformed into amorphous, destroying the crystal structure of multilayers, and the hardness also decreases. Due to the high deposition rate, this technique, which uses chemical sputtering method to synthesize TiN/AlON multilayer, is of potential industrial application.3. In AlN/TiB₂ nano-multilayers, due to the template effects of AlN, the amorphous TiB2 layers are forced to crystallized and grow epitaxially with h-AlN at small thickness. At the same time, the hardness of multilayers increases up to 30.5GPa. Further increasing the thickness of TiB2 layers, the TiB2 layers turn into amorphous, and destroying the epitaxial structure of multilayers, accordingly the hardness decreases.4. Based on Stoney equation, a method is proposed to measure the internal stresses in the metal based thin films, which releases the stresses by cutting metal substrate with eletro discharging machining （EDM）. With this method, the internal stresses can be conveniently and rapidly measured.更多还原