采用磁控溅射法制备了不同Al含量的Ti1-xAlxN涂层. 经XRD, SEM, EDX和纳米压痕仪分析发现, Al含量在0.50~0.58 (原子分数, 下同)之间时, Ti1-xAlxN涂层为(111)择优生长的fcc结构. 当Al含量增加到0.63时, 涂层中有六方纤锌矿结构的AlN生成, 涂层硬度降低. 另外, 随着Al含量的增加, 涂层表面颗粒尺寸变大, 涂层变疏松. 钛合金切削实验表明, 涂层刀具的磨损形式主要为黏结磨损和崩刃. 在低速切削(65 m/min)时, Ti0.50Al0.50N涂层刀具的切削性能略好于无涂层刀具, 并且都好于Ti0.42Al0.58N和Ti0.37Al0.63N涂层刀具. 在高速切削(100 m/min)时, Ti0.50Al0.50N涂层刀具有最好的切削性能, 其切削距离比无涂层刀具提高4倍多. 这主要因为Ti0.50Al0.50N涂层表面致密、硬度高, 在钛合金切削时形成的切屑瘤致密而整齐.
High-strength lightweight titanium alloy structural materials have been widely used in aerospace and other industry. However, the titanium is hard to machine due to its characteristics of low thermal conductivity, high chemical affinity and low elastic modulus. Coating tools provide a solution to overcome the problem of cutting titanium alloy. Ti1-xAlxN coating is one of the most popular candidates in cutting titanium alloy. However, the cutting performance and wear mechanism of the sputtering Ti1-xAlxN coating should be studied further in order to meet the demands of cutting titanium alloy. In this work, Ti1-xAlxN coatings with different Al contents have been prepared by magnetron sputtering. Microstructure and mechanical properties of the coatings were examined by XRD, SEM, EDX and nanoindenter. Results show that the coatings is a single fcc structure with a (111) preferred orientation when x is in the range of 0.50~0.58 (atomic fraction). When the Al content is 0.63, the hexagonal AlN is formed in the coating and the hardness declines. In addition, the surface particle size of Ti1-xAlxN coatings increases and the coating density decreases with increasing the Al content. The results of titanium cutting experiment indicate that the tool wear is mainly adhesive wear and chipping. The cutting performances of Ti0.50Al0.50N coated tool is slightly better than uncoated tool and are much better than those of Ti0.42Al0.58 and Ti0.37Al0.63N coated tools at a lower cutting speed (65 m/min). The cutting performance of Ti0.50Al0.50N coated tool is the best at a higher cutting speed of 100 m/min and is four times larger than that of uncoated tool. The excellent cutting performance of Ti0.50Al0.50N coating is mainly due to its high surface density and high hardness, which lead to the formation of regular and dense built-up edge during titanium cutting. Therefore, Ti0.50Al0.50N coating with a (111) preferred orientation, dense surface and relatively low Al content is recommended in high speed turning titanium.
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