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1、上海交通大学硕士学位论文 摘 要 I摘 要 高速切削和干式切削等加工技术的发展有力地推动了制造业的技术进步刀具硬质涂层材料性能的提高是其关键技术之一高硬度和优良的抗氧化能力是刀具涂层的重要性能指标以 TiN 为代表的陶瓷硬质薄膜已广泛应用于刀具涂层并取得巨大成功在 TiN 薄膜基础上加入金属元素如 AlCrZr 等可以进一步提高薄膜的硬度和抗氧化性其中(Ti,Al)N 薄膜的硬度约 35GPa和高温抗氧化能力约800均较 TiN 薄膜有很大提高成为目前最常用的刀具涂层材料然而高速切削和干式切削时刀具前端的温度可达 1000目前的常用涂层尚不能达到如此高的抗氧化温度因此进一步提高硬质薄膜的抗氧化
2、性能成为涂层发展的关键在(Ti,Al)N 涂层中加入氧以取代部分氮形成含氧化合物涂层有望提高其高温抗氧化性并具有优良的力学性能 本文首先采用镶嵌复合靶反应溅射技术研究了 Ti-Al-N 体系中的富 Ti 的(Ti,Al)N 薄膜和富 Al 的(Al,Ti)N 薄膜的制备工艺和薄膜的微结构与力学性能在此基础上采用在反应气体中加入氧气的方法进一步研究了 Ti-(Al)-O-N 体系中富 Ti的(Ti,Al)(O,N)薄膜富 Al 的(Al,Ti)(O,N)薄膜和 Ti(O,N)薄膜的制备技术及工艺参数对薄膜微结构和力学性能的影响规律获得了一系列高硬度的 Ti-(Al)-O-N 薄膜这类薄膜有望具有
3、更高的抗氧化温度从而成为新一代刀具涂层材料本文得到的主要结果如下 1. 采用反应溅射法制备的 Ti-Al-N 薄膜在制备过程中溅射靶表面 Ti:Al 保持不变由于靶面上 TiN 的生成自由能低于 AlN氮分压的改变会对薄膜的沉积速率化学组分微结构和力学性能带来重要影响低的氮分压下薄膜形成负氮化合物Ti:Al 比较高沉积速率亦较高随着氮分压的提高薄膜中氮含量提高形成化学计量比的(Ti,Al)N 和 (Al,Ti)N 薄膜薄膜中的 Ti:Al 比逐渐减小沉积速率也降低氮分压过高时由于存在靶中毒现象尽管薄膜的成分无明显变化但沉积速率大大降低 2. Ti:Al比约为 1:1 的(Ti,Al)N 薄膜和
4、 Ti:Al比约为 1:2 的(Al,Ti)N 薄膜均致密上海交通大学硕士学位论文 摘 要 II 平整与基体结合良好两种薄膜都为 NaCl结构晶粒细密并呈现(111)取向薄膜的最高硬度和弹性模量分别为(Ti,Al)N 薄膜 HV=34.4GPaE=392GPa(Al,Ti)N 薄膜 HV=36.9GPaE=476GPa 3. 在反应溅射法制备 Ti-Al-N 系薄膜的基础上加入少量的氧气作为反应气体形成 ArN2O2混合气体可以方便地制备出高硬度的 Ti-Al-O-N 薄膜随氧分压的提高薄膜中氧含量逐步增加氮含量相应减少而(Ti,Al)(O,N)薄膜中 Ti:Al比逐渐降低 (Al,Ti)(O
5、,N)薄膜中Ti:Al比逐渐升高 但都趋向于1:1 薄膜仍保持(Ti+Al):(O+N)约为 1:1 的化学计量比并且薄膜的沉积速率基本保持不变 4. 微结构和力学性能研究表明Ti-Al-O-N 薄膜仍保持与 Ti-Al-N 薄膜相同的NaCl结构 但随氧含量的提高逐步呈现强烈(200)织构的柱状晶 与此同时 Ti-Al-O-N薄膜的硬度和弹性模量也仍保持在与Ti-Al-N 薄膜相当的35GPa和370420GPa的高值由于薄膜中形成了相当含量的氧化物这类薄膜的抗氧化能力有望得到提高 5. 采用 Ar+N2+O2的混合气体可以方便地制备 Ti(O,N)薄膜随氧分压的增加薄膜中的氧含量增加薄膜仍
6、保持与 TiN 相同的 NaCl 结构加入氧的 Ti(O,N)薄膜的硬度约 26GPa较 TiN 的硬度约 21GPa有所提高而其弹性模量在低氧含量时由 TiN365GPa提高到 411GPa5.0at%O后又随氧含量的增加而逐步降低 关键词多元硬质薄膜反应溅射Ti-Al-N 薄膜Ti-Al-O-N 薄膜Ti-O-N 薄膜微结构力学性能 上海交通大学硕士学位论文 摘 要 IIIABSTRACT High-speed cutting and dry machining significantly promote the progress in modern processing technolo
7、gy. Coating property is one of its cruxes, to which more and more attentions have been paid for many years. Particularly, most of the related researches are focused on the improvement of coating hardness and oxidation-resistance, which are two most important criteria for their performance under extr
8、eme conditions. Ceramic hard coatings, such as TiN, have been successfully employed as tool coatings in many fields. In TiN coating, alloying additional metal elements, such as Al, Cr, Zr, etc, can drastically improve its oxidation resistance and hardness. For example, (Ti,Al)N coating, incorporated
9、 with aluminum in TiN coating, has a higher hardness (35GPa) and superior oxidation resistance (800) and becomes one of the leading coatings. However, in high-speed cutting and dry machining, the temperature at the forepart of tools may reach 1000, under which none of current coatings can keep stabi
10、lization. Therefore, it is crucial to improve the oxidation resistance of coatings. And it is promising to improve the coatings oxidization resistance by adding oxygen in (Ti,Al)N coating as a result of part of nitrogen atoms being replaced by oxygen atoms to form an oxide-composed hard coating. In
11、this paper, firstly we detailedly studied the preparation technics, microstructures, and mechanical properties of reactively sputtered (Ti,Al)N films rich in Ti and (Al,Ti)N films rich in Al using mosaic targets in the mixture gases of Ar and N2. Based on this work, we synthesized (Ti,Al)(O,N) films
12、, (Al,Ti)(O,N) films, and Ti(O,N) films by adding O2 into the gases and studied the influence of preparation technics and parameters on the microstructures and mechanical properties of these films. These films are promising to have superior oxidization resistance and become the leading hard coatings
13、 as a new generation. The main results of this study are summarized as follows. 1. In the preparation of Ti-Al-N films, because the ratio of Ti to Al on the mosaic target surface is kept constant and the heat of formation of TiN is less than that of AlN, N2 上海交通大学硕士学位论文 摘 要 IV partial pressure has a
14、n important effect on the deposition rates, chemical compositions, microstructures, and mechanical properties of the films. At low N2 partial pressure, the films form nitrides lack of nitrogen. The ratio of Ti to Al and deposition rate of the films is high. With the increase of N2 partial pressure,
15、(Ti,Al)N and (Al,Ti)N films with stoichiometric ratio are obtained; the ratio of Ti to Al and deposition rate decrease gradually. At overhigh N2 partial pressure, the deposition rate decreases greatly due to the target poisoning but the composition of the coatings has almost no change. 2. (Ti,Al)N films whose Ti/Al ratio is about 1:1 and (Al,Ti)N films whose Ti/Al is about 1:2 are all compact and well adhere to the substrates. The films present B1 NaCl structure and the grains are fine, exhibiting (111) preferred orientation. The m aximum hardness and elastic modulus of (Ti,A
