| Summary: | 碩士 === 國立臺灣海洋大學 === 材料工程研究所 === 107 === In this study, Cr–Si–N coatings were fabricated using reactive direct current magnetron sputtering system. Fixed nitrogen partial pressure N2/(Ar+N2) is 0.5, The Cr target power is 100 W, and the Si target power is changed from 0 to 150 W. Microstructure, phase structure, mechanical properties and oxidation resistance of the Cr–Si–N coatings are analyzed to find out the effect of Si incorporation on Cr–Si–N coating. The results indicated that the Cr–Si–N coatings with a Si content of < 14 at.% exhibited a cubic CrN phase, whereas further increasing the Si content of the coatings resulted to form an amorphous phase. All the X-ray diffraction reflections of the crystalline coatings shifted to higher angles related to the standard values of a CrN phase and the deviations increased with increasing the Si content. The cross-sectional transmission electron microscopy images of the crystalline coatings with 5 at.% Si exhibited a columnar structure, whereas the coatings with 14 at.% Si comprised nanoscale crystals and the coatings with 19 at.% Si seemed amorphous. In terms of mechanical properties, the hardness increases as the Si content increases. Cr32Si14N54 possessed the highest hardness and Young’s modulus of 17 GPa and 204 GPa, respectively. The addition of Si was also beneficial to reduce the surface roughness. The roughness level of the coatings with a Si content higher than 16 at.% was less than 1 nm. Scratch tests and HRC-DB tests indicated that the adhesion strength was related to the coatings phase structures. LC1 and LC2 levels decreased abruptly as the phase structure changed from crystalline to near-amorphous. The crystallized Cr–Si–N coatings maintains LC1 and LC2 values at approximately 13 and 23 N, respectively. The results of the HRC–DB test show Cr–Si–N coatings have good adhesion and exhibits an adhesion level of HF1–HF3. When the Si content is <14 at.%, very tiny delamination are found through SEM images.
In order to evaluate the feasibility of applying Cr–Si–N coatings in glass molding process, the heat treatment was carried out in a simulated molding environment of 15 ppm O2–N2, and 600 °C for 8 and 16 hours. The variation on the phase structure, roughness and mechanical properties were investigated. The results indicated that the lattice constant of the coating decreases to the same value as the standard value after heat treatment, and the microstructure changes to improve the mechanical properties of the coating. The Cr2O3 phase was not observed in Cr–Si–N coatings with Si content >14 at.% after heat treatment. The increased oxidation resistance was attributed to the formation of amorphous SiO2 layer on the coating surface.
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