Papers by Author: Shi Cheng Wei

Abstract: A corrosion-resistant and wear-resistant coating was prepared on the inner wall of copper tube by centrifugal self-propagating melting. The surface morphology, composition and phase composition of the ceramic lining FGM coating were analyzed by XRD and SEM, and the synthesis mechanism of the ceramic coating was studied. The results show that the functionally gradient coating is composed of three layers: ceramic inner layer, metal transition layer and copper substrate layer. The surface of ceramic lining is smooth and dense, which is mainly composed of Al₂O₃, CaF₂ and a small amount of Fe Al spinel. The results show that the alumina phase is dendrite like and grows outward perpendicular to the tube wall, and the low melting point phase is evenly distributed in the dendrite gap, which effectively improves the density of the ceramic layer.

Abstract: The inner-lined layers bonding strength of the ceramic-lined tubing was measured from 25°C to 600°C. The macroscopic structure and microscopic characteristics of the slippage surface of the ceramic-lined tubing were observed using optical microscopy and scanning electron microscopy. Combined with finite element analysis of the residual stress distribution at different temperatures, the shear failure model of the ceramic-lined tubing at different temperatures was given. The mechanical bonding force at the C-A (ceramic layer-alloy layer) interface is greater than the metallurgical bonding force at the A-T (alloy layer-base tubing) interface at low temperature, and the mechanical bonding force at the C-A interface is less than the metallurgical bonding force at the A-T interface at high temperature. The transition temperature is about 200 °C.

Abstract: Electrochemical impedance spectroscopy (EIS) is a technology of nondestructive electrochemical testing. In this paper, EIS is applied to study the corrosion processes of Al-Mg coatings. In the initial 24 h of immersion in 3.5% NaCl solution, passive films of Al-Mg coatings dissolve quickly. As time passed, corrosion products increase on surface gradually, which can inhibit corrosion. After 480h of immersion, corrosion products fully cover on Al-Mg coatings’ surface. The EIS of different corrosion processes are fitted by three equivalent circuits corresponding to the three corrosion processes. In the test of open circuit potentials (OCP), OCP is instable in the initial 24 h of immersion. As immersion time goes by, OCP tends to stabilization at about -0.90 V. Measurements of scanning electron microscope (SEM) confirm the conclusions of electrochemical measurements.

Abstract: This paper mainly introduced the causations of deep-sea submersible (DS) surface material damage and some methods of research on corrosion and fatigue. It is suggested that investigating the mechanisms and effects of corrosion and fatigue damage on DS steel structure and coating, and the mapping relation for the origin and accumulation of cross scale damage should be established. In addition, organic coating, metallic coating, steel matrix and their interaction could be detected and analysed using the methods of SEM, XRD, TEM, EIS, EN, CV, Kelvin probe and so on. At last, mathematical model of service life for the steel structure and coating should be established for the quantification study

Abstract: Spraying wire was widely used in remanufacturing work piece for worn failure. With the demand of high abrasion resistant wire, new type alloy was developed. The solidification structures of the new high abrasion resistant alloy (HARA) containing Mn, Cr, Si, C and the structure was studied after tension by scanning electron microscopy (SEM). The phase evolution was analyzed by X-ray diffraction and Rockwell hardness evaluated on the hardness testing. The abrasion behavior of HARA alloy used in the liner of wet-grinding machine in metallurgical industry is investigated under impacted energy of 0.5-3 J in acid-ironstone slurry; the test was carried out by a modified MLD-10 tester. The result show that the solidification structures of HARA alloy consist of austenitic Fe and the hardness neared to HRC60. Under the high energy, the wear resistance of HARA alloy is three times more than Mn13. Therefore, the new material has better abrasive wear resistance and lower environmental impact

Abstract: This paper reports on a new clad technology that is protective coating cladding. The method is that the Ni60 alloy was prepared on 0.45%C steel and high temperature powder paste brushed on the outside. Then the sample after being dried was heated in the high temperature resistance electric furnace. The Ni60 alloy powder on the substrate steel was melted at the appropriate temperature, and a uniform, adherent and non-dilution clad coating was obtained after optimizing the cladding parameters. The coating microstructures, compositions and microhardness were analyzed by OPM, XRD, EPMA, and microhardness testing. The experimental results show that the protective coating cladding is an efficient and economic method in cladding technologies

Abstract: An automatic high velocity arc spraying process was used to deposit a type of FeCrBSiMoNbW amorphous/nanocrystalline coating with substrate of AZ91 magnesium alloy. The microstructure of the coating was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDAX). The coating is about 250μm in thickness with low porosity and oxids. The results show that the microstructure of the coating can be classified into two regions, namely, a full amorphous phase region and homogeneous dispersion of α-Fe (Cr) nanocrystals with 30-80 nm in a residual amorphous region. Mechanical properties, such as nano-hardness, elastic modulus, were analyzed. The experimental results show that the coating has high nano-hardness and elastic modulus. The friction and wear experiments were operated on UMT-2 micro friction tester. The relative wear resistance of the FeCrBSiMoNbW coating is about 2 times higher than that of the conventional 3Cr13 coating under the same conditions. The main wear mechanism of the amorphous/nanocrystalline coating is the typical brittle spalling.

Abstract: A metal coating corrosion monitoring system (CMS) based on corrosion potential was introduced. It’s working principle, especially the design and selection of soft and hardware and the main technical specifications. The system has the characters of real-time monitoring of changes in corrosion potential status of coatings, automatically storing corrosion information and alarming according to corrosion degree in monitoring sites.

Abstract: The corrosion behavior of Al-RE coating in copper accelerated acetic acid salt spray test (CASS) was studied by electrochemical impedance spectroscopy (EIS). Typical EIS spectral changes were clearly observed during the CASS process. The EIS was shown to be a very useful tool for studying corrosion resistance mechanism. Scanning electron microscope and X-ray energy dispersive spectroscopy were used to analyze the microstructure of Al-RE coatings before and after CASS test. The results revealed that the corrosion behavior of Al-RE coating could be divided into two different stages. In the first stage of CASS, there were two capacitive impedance semicircles in the complex plane plots. The high frequency semicircle responded to barrier layer, the low frequency semicircle responded to the electrochemical reaction of Al-RE coating. In the second stage of CASS, porous layer began to influence the electrochemical behavior.

Abstract: The most severe corrosion of offshore steel structure occurs in splash zone. There are many factors affecting the steel structure corrosion in the splash zone, such as corrosion problems caused by seawater and effect of impacted brought by the ocean wave. Considering the corrosion characteristics in splash zone and the corrosion invalidity behaviors of offshore steel structure, the Zn-15Al, Al-RE, Zn-Al-Mg-RE and FeBSiNb uncrystal coatings were prepared by automatic high velocity arc spraying. The different anti-corrosion behaviors of the four coatings were studied through the corrosion comparative tests and the microstructures analyzed of the coatings before and after the corrosion tests. The anti-corrosion coating systems suitable for using on surface of steel structure corrosion in the splash zone were found, which provided technique guarantee for extending the using life of offshore steel structures.