Sheng Han

The cavitation-erosion phenomenon of chromium nitride coatings deposited using cathodic arc plasma deposition on steel

Abstract The cavitation-erosion behavior of chromium nitride (CrN) coatings on AISI 4140 steel in fresh water and 3.5% NaCl solution has been investigated using an ultrasonic vibration system. The CrN coatings were deposited by cathodic arc plasma deposition (CAPD) with and without an intermediate layer of electroplated hard chrome, i.e. CrN/AISI 4140 and CrN/Cr/AISI 4140. The composition and structure of the CrN coatings have been studied using X-ray diffraction (XRD), using θ/2θ diffraction mode and Schulz reflection methods, which revealed a preferred orientation of CrN(220) for CrN/Cr/AISI 4140. The microstructure and crystalinity of the CrN coatings have been examined using cross-sectional transmission electron microscopy (XTEM). Both CrN/AISI 4140 and CrN/Cr/AISI 4140 coatings exhibited strong microcolumnar structures, however, the shape and grain size of the coatings were approximately the same. In addition to the microstructural investigations, cavitation-erosion tests were conducted under free corrosion conditions in fresh water and in chloride containing water. Subsequent electrochemical evaluation was made to elucidate the mechanism of cavitation-erosion. The resulting mechanical damage has been assessed using weight loss measurements and scanning electron microscopy (SEM) observations. Notwithstanding a significant improvement in the cavitation resistance of the coated specimens in fresh water and NaCl solution, the damage resulting from the cavitation-erosion in the 3.5% NaCl solution exhibited a higher weight loss than those in freshwater.

The effect of preferred orientation on the mechanical properties of chromium nitride coatings deposited on SKD11 by unbalanced magnetron sputtering

Abstract Chromium nitride coatings exhibit good mechanical, corrosion and oxidation protection properties and can have various orientations. Preferred orientations of CrN(200) and Cr 2 N(111) were successfully deposited on SKD11 by unbalanced magnetron sputtering. To compare with different orientations, several mechanical properties of deposited films were studied, e.g. hardness, adhesion and wear behavior. The structural characterization and surface morphology were investigated using atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The chemical composition and stoichiometry were determined using X-ray photoelectron spectroscopy (XPS). The cross-section morphology of CrN coating is a columnar structure and Cr 2 N is a denser structure. Of the two orientations CrN(200) and Cr 2 N(111), CrN(200) possesses stronger adhesion and lower hardness.

Phase transformations in copper oxide nanowiresa)

Cu nanowires were electrodeposited into the nanopores of self-ordered aluminum oxide films. CuO and Cu2O nanowires were fabricated by oxidizing Cu nanowires in air. Cu nanowires oxidized at 250°C transform only to Cu2O (grain size ∼21nm), they transform to a mixture of CuO and Cu2O above 350°C and finally to CuO with a preferred orientation of CuO (111) at 900°C.

Effect of metal vapor vacuum arc Cr-implanted interlayers on the microstructure of CrN film on silicon

c Abstract The effect of metal vapor vacuum arc (MEVVA) Cr-implanted interlayers on the microstructure of CrN films on the silicon wafer was investigated.Two types of the CrN-coated specimens (CrNySi and CrNyCrySi) by cathodic arc plasma deposition were prepared with and without a MEVVA Cr-implanted interlayer.The diffraction patterns of the coated specimens revealed the presence of CrN, and the (220) preferred orientation for both CrNySi and CrNyCrNySi.The CrN coating thicknesses for CrN y Si and for CrNyCrySi were 0.3 mm and 1.3 mm, respectively.Secondary ion mass spectrometry proved the high quality of the films on silicon substrates.Transmission electron microscopy micrographs and selective area diffractions revealed the presence of a large number of nano-scale Cr resulting from the interlayer of MEVVA Cr with a background of single crystal silicon spots. Furthermore, in situ stress measurement demonstrated that the presence of a Cr interlayer between CrN and Si could drastically reduce the residual stress in the CrNyCrySi assembly. 2003 Elsevier Science B.V. All rights reserved.

The effect of MEVVA implanted Cr on the corrosion resistance of CrN coated low alloy steel by cathodic arc plasma deposition

Abstract Metal vapor vacuum arc (MEVVA) source implantation is a novel and profitable surface modification process. Cathodic arc plasma deposition of CrN coating has been applied on an industrial scale to improve the corrosion resistance of AISI 4140 steel. The effect of the Cr implanted by MEVVA (Cr/steel) on the corrosion behavior of CrN/steel through the surface modification was investigated. Both AISI 4140 steel and its coated assemblies of Cr/steel, CrN/steel and CrN/Cr/steel were evaluated in aerated 0.1 N HCl solution. The composition and structure of the MEVVA implanted Cr and cathodic arc plasma deposited CrN on steel were studied by X-ray diffraction and secondary ion mass spectrometer. The polarization resistance ( R p ) of all samples was measured and compared with d.c. polarization resistance and electrochemical impedance spectroscopy. The microstructure of corroded samples was also examined by scanning electronic microscopy and electron probe X-ray microanalyser. The results indicated that the corrosion resistance of CrN coated steel was significantly enhanced by the MEVVA implanted Cr in CrN/Cr/steel.

Aluminum nitride films synthesized by dual ion beam sputtering

Aluminum nitride films were deposited by varying the voltages of argon ion beams from 400 to 1200 V in dual ion beam sputtering. The crystal structure, microstructure, and elemental distributions of the aluminum nitride films were analyzed by x-ray diffraction, field emission scanning electron microscopy, and secondary ion mass spectroscopy, respectively. The aluminum nitride films exhibited the 〈002〉 preferred orientation at an optimal ion beam voltage of 800 V. The orientation changed to a mixture of {100} and {002} planes above 800 V, accounting for radiation damage. The thickness of the film increases with increasing ion beam voltage, reaching a steady state value of 210 nm at an ion beam voltage of 1200 V. Under optimal condition (800 V), the c-axis orientation of the aluminum nitride 〈002〉 film was obtained with a dense and high-quality crystal structure.

Effect of metal vapor vacuum arc-implanted Cr on the electrochemical behavior of CrN-coated steels

Using cathodic arc plasma to deposit CrN on the steel has been explored and extensively studied to improve the wear and corrosion resistance of the steel structures. Metal vapor vacuum arc (MEVVA) source implantation is a novel and profitable surface-modification process coupled with the cathodic arc plasma. The effect of the MEVVA-implanted chromium on the corrosion behavior in form of Cr/steel, CrN/steel, and CrN/Cr/steel was evaluated in an aerated 0.1N HCl solution. The composition and structure of the MEVVA-implanted chromium and the cathodic arc plasma deposited CrN on steel were both examined by x-ray diffraction and transmission electron microscopy. The polarization resistance ( R p ) of all samples was measured and compared with the results obtained from electrochemical impedance spectroscopy simulated by the equivalent circuit, to interpret the effect of MEVVA-implanted chromium on the corrosion mechanism of the CrN/Cr/steel. The corrosion products associated with the microstructures were analyzed by electron probe x-ray microanalyzer. The results indicated that the corrosion resistance of the CrN-coated steel was significantly enhanced by the MEVVA-implanted chromium in the CrN/Cr/steel assembly.