Mechanical Properties and Cutting Performance of Multilayered AlTiN/CrTiSiN Hard Coatings

• Main Authors: CHAO, LIANG-CHAN, 趙良展
• Other Authors: CHANG, YIN-YU
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/3u8sw7

碩士 === 國立虎尾科技大學 === 機械與電腦輔助工程系碩士班 === 107 === 　　Transition metal nitride coatings based on Cr, Ti and Al, such as AlTiN, AlCrN and AlCrSiN, have been used as protective coating materials of cutting and forming tools due to their high hardness and thermal stability. In this study, AlTiN and AlCrSiN and AlTiCrSiN coatings were deposited onto tungsten carbide tools using AlTi, TiSi, Cr and ternary AlCrSi alloy targets in a Cathodic-arc evaporation (CAE) system. Optimal design of interlayers of the AlCrSiN and AlTiCrSiN can offer an efficient way of controlling residual stress, improving adhesion strength and enhancing toughness. By controlling the different interlayers and negative bias voltages, the AlCrSiN and AlTiCrSiN possessed different microstructures and mechanical properties. 　　The microstructure of the deposited coatings was investigated by field emission scanning electron microscope (FE-SEM) and field emission gun high-resolution transmission electron microscope (FEG-HRTEM), equipped with an energy-dispersive x-ray analysis spectrometer (EDS). Glancing angle X-ray diffraction was used to characterize the microstructure and phase identification of the coatings. Mechanical properties, such as the hardness and young’s modulus, were measured by means of nanoindention. The adhesion strength of the coatings was evaluated by a standard Rockwell indentation test. In order to evaluate the impact fatigue behavior of the coated samples, an impact test was performed using a cyclic loading device with a tungsten carbide indenter as an impact probe. For the cutting experiment, 316L stainless steel was machined by the coated end mills under oil mist condition using a CNC milling machine. 　　According to the experimental result, it showed that AlTiCrSiN were nanocomposites coatings composed of nanocrystalline B1-NaCl structure and amorphous phase structure. The interaction between the grains hindered the generation of dislocations and prevented cracks propagation due to the suppression of grain boundary sliding. The design of multilayered AlTiCrSiN-100V coatings possessed the higher hardness of 40GPa, plastic deformation resistance, impact resistance (higher than 7× 10^5 impacts) and wear resistance. The crystalline phase does not change after high-temperature oxidation and still maintains excellent mechanical properties with thermal stability. For the ball-on-disk wear tests, the as-deposited AlTiCrSiN-20V and which after 800˚C annealing in air possessed the lowest wear rates of 8.9 x 10^(-7) (mm^3/Nm) and 1.1 x 10^(-6) (mm^3/Nm), respectively. According to the cutting test results, the AlTiCrSiN-20V showed the minimum end cutting edge wear, which can effectively improve the machinability and tool life. Thus, the AlTiCrSiN coatings with a multilayered structure of AlTiN and CrTiSiN showed the best wear resistance and cutting performance of 316L stainless steel.