【作者】 杜日昇；

【导师】 彭继华；

【作者基本信息】 华南理工大学 ， 材料加工工程， 2011， 硕士

【摘要】 随着现代机械加工向着高速切削及干式切削技术方向的发展,对工具涂层的要求越来越高,即高结合力、高硬度、高红硬性。Ti-Al-N系硬质涂层已在国内外得到广泛研究和应用。但铝含量及涂层的结构对涂层综合力学性能及抗氧化性能影响的系统研究报道不多。本文重点展开这两方面的研究探讨,具有一定的理论和实践意义。本文采用多弧离子镀技术,利用纯Ti靶及TiAl合金靶,在SKH51高速钢表面沉积Ti-Al-N系硬质涂层,优化了制备高铝含量Ti_0.33Al_0.67N涂层及TiN/Ti_0.33Al_0.67N多层结构涂层的制备工艺。采用材料表面性能测试仪、显微硬度计、扫描电镜、X射线衍射仪、电子探针仪等系统研究了Al含量及多层结构对涂层表面形貌、相结构、显微硬度、膜基结合力及高温抗氧化性能的影响规律。研究结果表明:1、在基体偏压为80V（占空比50%）,TiAl靶电流为70A,N₂气压为3.0×10^-1Pa的条件下,制备出厚度2～2.5μm的Ti_0.33Al_0.67N涂层显微硬度可以达到3100HV0.01,结合力达到49N。2、不同Al含量的单一结构Ti_1-xAl_xN涂层及多层结构的TiN/Ti_1-xAl_xN涂层都由fcc结构的（Ti,Al）N相组成,并随着Al含量的增加衍射峰的位置向右偏移（2θ变大）,晶格常数变小。3、单一结构和多层结构的涂层都呈致密的柱状晶结构;单一结构涂层的断口呈完整柱状晶撕裂方式,而多层结构涂层断口在局部区域呈明显的短纤维状。4、与单层结构的Ti_1-xAl_xN涂层比较,多层结构的TiN/Ti_1-xAl_xN涂层可以在基本保持显微硬度的情况下,较大幅度地提高膜-基结合力。5、Ti_1-xAl_xN涂层保温1小时起始氧化临界温度Tc随着涂层中Al含量的增加单调增加。Ti_0.33Al_0.67N涂层保温1小时起始氧化温度接近900℃。6、无论单层结构还是多层结构,800℃条件下氧化增重服从抛物线规律,氧化增重速率K_p值随着Al的增加减小。与单层结构的Ti_1-xAl_xN涂层比较,多层结构的TiN/Ti_1-xAl_xN涂层抗氧化性能有所降低。7、致密的Ti_1-xAl_xN涂层能够有效地阻止基体金属中合金元素的扩散,但大尺寸金属熔滴同涂层之间形成的界面是氧及基体金属元素扩散的快速通道。由于熔滴存在,减少了涂层阻挡层厚度。涂层氧化起始的临界温度及时间同形成Fe₂O₃产物密切相关。更多还原

【Abstract】 Due to the demanding requirement from advanced machining and processesing, machining tools call for advanced coating with high hardness, strong adhesion and excellent oxidation performance. Upto now, Ti-Al-N coating has been extensively researched and developed over the world. However, there is less systematic study on the effect of Al content and architecture structure of Ti-Al-N coatings on their combined mechanical propertie and oxidation behavior. This paper pays more attention on these two aspects.By means of multi-arc ion plating with pure Ti and TiAl alloy targets, Ti-Al-N hard coatings were deposited on SKH51 high speed steel substrate. The microhardness, and the adhesion strength between the coating and substrate were tested by multi function tester of material’s surface properties, microhardness tester. Eelectron microscopy, X-ray diffraction and electron probe analysis system were used to characterize the constituent phases and microstructure of the coating before or afteranealing. The following conclusion can be made:1. The microhardness and adhesion of Ti_0.33Al_0.67N monolayer coating with thickness of 2 2.5μm can reach 3100 HV_0.01, and 49N respectively, when the substrate bias voltage is 80V （duty cycle 50%）, TiAl target current is 70A and N₂ pressure is 3.0×10^-1Pa.2. All the Ti_1-xAl_xN monolayer and TiN/Ti_1-xAl_xN multilayers coatings with different Al content are composed with f.c.cδ-TiNstructure. With Al content increasing, the position of diffraction peaks shift toward right, which means the lattice cell size decreases.3. The Ti_1-xAl_xN monolayer and the TiN/ Ti_1-xAl_xN multilayers coatings all exhibited dense columnar structures.The tear-off of a solid whole columnar crystal is the main fracture mode for the monolayer coating, while short fiber-like fracture is found in some area for multilayer coating.4. Comparing with Ti_1-xAl_xN monolayer coating, TiN/Ti_1-xAl_xN multilayer coating improve the film–substrate adhesion significantly, without less microhardness loss.5. When annealing for 1 hour, the critical initial oxidation temperature Tc of Ti_1-xAl_xN coating increases monotonously with Al content increasing. Tc of Ti_0.33Al_0.67N coating specimens is close to 900℃.6. Annealing at 800℃, both monolayer and multilayer coating obey the parabolic law of oxidation weight gain. The oxidation weight gain speed coefficient Kp value decreases with the Al contet rising. Compared with monolayer coating, oxidation resistance of multilayer coatings deceased.7. Diffusion of substrate metal elements could be prevented effectively by dense Ti_1-xAl_xN coating. The rapid diffusion channels would be formed at the interface between melt-droplets the coating. The critical temperature and critical time of Ti-Al-N coating specimens related closely with the formation of Fe₂O₃ oxide.更多还原