Effect of Arc Currents on the Mechanical, High Temperature Oxidation and Corrosion Properties of CrSiN Nanocomposite Coatings

In methods for multi-arc ion plating technology, the behavior and characteristics of the arc spot determine the physical characteristics of arc plasma and the properties of the subsequent deposited coatings. In this paper, the effect of arc currents on the hardness, friction coefficient, high temperature oxidation, and corrosion properties of the CrSiN coatings was studied. According to the XRD and SEM results, with the increase of arc currents, the coatings grew preferentially to the CrN (111) crystal direction, and the CrN (220) crystal phase appeared at high currents of 90 A. In addition, the number of large particles increased when the current exceeded 70 A. The HR-TEM results confirmed the formation of nanocomposite structure of nanocrystalline of CrN embedded into the amorphous phase of Si3N4 as explored by XRD. The maximum hardness was achieved at 3120 Hv when the coatings were deposited under currents around 70 A. However, the hardness values decreased with further increase of arc currents. From the contact of ceramic balls with the wear of coatings, the surface of coatings gradually produced friction marks, and the friction force increased from a steady friction force to a dynamic friction force. The high temperature oxidation results showed that fewer oxides were formed on the surface of the coatings when oxidized at 800 °C. It was also found that CrSiN nanocomposite coatings prepared at an arc current of 70 A had a larger corrosion potential and polarization impedance, which could effectively protect the tool matrix

Effects of Bias Voltages on the Structural, Mechanical and Oxidation Resistance Properties of Cr–Si–N Nanocomposite Coatings

Cr–Si–N nanocomposite coatings were deposited by multi-arc ion plating under different bias voltages. The influences of bias voltage on composition, microstructure, surface morphology and mechanical properties of Cr–Si–N nanocomposite coatings were investigated in detail. The HR-TEM, XRD, and XPS results confirmed the formation of nanocomposite structure of nanocrystalline of CrN embedded into the amorphous phase of Si3N4. The particle radius of CrN can be calculated from the half-width of the diffraction peak of CrN (200) and the value was about 20–60 nm. In addition, no diffraction peaks of CrSi2, Cr3Si, or Si3N4 were found in all the Cr–Si–N coatings. With the increasing of bias voltages from 0 to −200 V, the number and size of large droplets on the coating surface decreased, and the growth mode of the coatings changed from loose to dense. However, with the increasing of bias voltages from 0 to −200 V, the micro-hardness of the coatings increased and then decreased, reaching its maximum value at negative bias voltages of 100 V. It was found that the friction coefficient of Cr–Si–N coatings is almost the same except for the Cr–Si–N coatings deposited under bias voltage of 0 V. When the oxidation temperature was at 800 °C, the Cr–Si–N coating was only partially oxidized. However, with the increase of oxidation temperature to 1200 °C, the surface of the coating was completely covered by the oxide generated. The results showed that the bias voltages used in multi-arc ion plating had effects on the structure, mechanical, and high temperature oxidation resistance properties of Cr–Si–N nanocomposite coatings

Wear and Corrosion Resistance of CrYN Coating in Artificial Seawater

In this study, CrYN coatings were prepared using multi-arc ion plating at various substrate bias voltages (−50 V, −100 V, −150 V, and −200 V). X-ray diffractometry and scanning electron microscopy were used to characterize the composition and microstructure of the coatings. An electrochemical workstation and a ball-on-disk tribometer were used to investigate their corrosion and friction behavior. The results show that grain refinement can be achieved through the addition of yttrium (Y) and that the surfaces of coatings prepared under different bias voltages have varying smoothness and compactness. It was shown that surfaces prepared under −100 V bias voltages were relatively smooth and dense in structure, corresponding to a Y content of 2.83 at.%; CrYN coatings at −100 V were shown to have the highest corrosion potential and a low self-corrosion current, equating to superior corrosion resistance. Additionally, the friction coefficients of deposited CrYN coatings under bias voltages of −100 V were less than 0.2. Therefore, the coatings under bias voltages of −100 V had the minimum wear rate due to its structure, corrosion resistance, and friction

A Polarization-Independent Fiber-Optic SPR Sensor

Fiber-optic surface plasmon resonance (SPR) sensors possess the advantages of small size, flexible, allowing for a smaller sample volume, easy to be integrated, and high sensitivity. They have been intensively developed in recent decades. However, the polarizing nature of the surface plasmon waves (SPWs) always hinders the acquisition of SPR spectrum with high signal-noise ratio in wavelength modulation unless a polarizer is employed. The addition of polarizer complicates the system and reduces the degree of compactness. In this work, we propose and demonstrate a novel, polarization-independent fiber-optic SPR sensor based on a BK7 bi-prism with two incident planes orthogonal to each other. In the bi-prism, TM-polarized components of non-polarized incident lights excite SPWs on the first sensing channel, meanwhile the TE components and the remaining TM components are reflected, then the reflected TE components serve as TM components of incident lights for the second sensing channel to excite SPWs. Simulations show the proposed SPR structure permit us to completely eliminate the polarization dependence of the plasmon excitation. Experimental results agree well with the simulations. This kind of devices can be considered an excellent option for development of simple and compact SPR chemical sensors