| Summary: | 碩士 === 東南科技大學 === 機電整合研究所 === 99 === Eleven nanostructured Cr-B-N thin films coatings were deposited by a bipolar asymmetric reactive pulsed DC magnetron sputtering system. Seven Cr-B-N thin films containing different B contents were obtained based on the distance difference between the Si substrate, CrB2 and Cr targets. On the other hand, Four Cr-B-N thin films containing various nitrogen contents were also deposited by a co-sputtering process. The vacuum annealing treatment was executed on the Cr-B-N thin films to evaluate the thermal stability, microstructure and mechanical properties evolution of each coating. The phase
structures of thin films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR), respectively. The cross-sectional morphologies of thin films were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The surface roughness of thin films was explored by an atomic force microscopy (AFM). A nanoindenter, a Vickers microhardness tester and a pin-on-disk wear tester were used to evaluate the hardness, fracture toughness and tribological properties of thin films, respectively. Electrochemical tests in 3.5 wt.% NaCl aqueous solution were performed to evaluate the
corrosion resistance of Cr-B-N coatings. The experimental results showed that when the boron content reached to 3.68 at.%, a high hardness, 21.7GPa, and elastic modulus, 183.6GPa, were achieved for the coating (#A1). Meanwhile, The Cr-B-N thin film (#B4) deposited under a nitrogen flow rate of 41.6%, the maximum hardness, 19.6GPa, and elastic modulus, 221.0GPa, were achieved.
The better thermal stability and the least hardness degradation were also found
for this coating.
It can be concluded that both the #A1 and #B4 coatings exhibited adequate mechanical properties and wear resistance, which are suitable as the protective coating on the cutting tools and car engine parts.
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