Cheng Jie

Bio: Cheng Jie is an academic researcher from Hohai University. The author has contributed to research in topics: Coating & Corrosion. The author has an hindex of 5, co-authored 21 publications receiving 87 citations.

Influence of the high-velocity oxygen-fuel spray parameters on the porosity and corrosion resistance of iron-based amorphous coatings

Abstract: In this paper, the high-velocity oxygen-fuel (HVOF) spraying technology was used to prepare the iron-based amorphous coatings onto the substrate of 45 steel. Three parameters of spray distance, oxygen flow and kerosene flow were optimized by the Taguchi method, with the porosity of the coatings as object. The statistical tools including orthogonal experimental design, signal-to-noise ratio and analysis of variance were used to optimize the spray parameters. The results indicated that the kerosene flow showed the highest effect on the porosity of the coatings, while the oxygen flow exhibited the least influence. It was found that the coating with lowest porosity was deposited under the spray distance of 380 mm, the oxygen flow of 1840 scfh, and the kerosene flow of 6.8 gph. The potentiodynamic polarization and electrochemical impendence spectroscopy (EIS) results manifested that the iron-based amorphous coating prepared with proper spray parameters exhibited superior corrosion resistance to the hard chromium coating. Besides, the coating with lower porosity exhibited better corrosion resistance than the coating with higher porosity.

Wet abrasive wear behavior of WC-based cermet coatings prepared by HVOF spraying

Abstract: In this study, three kinds of WC-based cermet coatings including WC–CoCr coating, WC–Ni coating and WC–Cr3C2–Ni coating were prepared by the high-velocity oxygen-fuel (HVOF) spraying process. Scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and Vickers hardness tester were used to analyze the microstructure and mechanical properties of these coatings. The WC–CoCr coating presented the highest average microhardness of 1205 HV0.3, and then followed by the WC–Cr3C2–Ni coating (1188 HV0.3) and the WC–Ni coating (1105 HV0.3). The abrasive wear behavior of the WC-based coatings under the conditions of different applied loads and sediment concentrations were studied by a wet sand-rubber wheel tester. The results indicated that the abrasive wear loss rates of all the coatings increased with the increment of applied load or sediment concentration. In addition, the coatings with higher microhardness appeared to have higher abrasive wear resistance. The abrasive wear resistance of the WC-based coatings was 4–90 times higher than that of AISI 304 stainless steel under the same testing condition. The abrasive wear mechanism of the WC-based coatings was deduced to be the extrusion and removal of binder phases, as well as the fragmentation and peel-off of hard phases.

Ultrasonic cavitation erosion mechanism and mathematical model of HVOF sprayed Fe-based amorphous/nanocrystalline coatings

Abstract: A Fe-based amorphous/nanocrystalline coating was prepared on the AISI 321 steel by the high-velocity oxygen-fuel (HVOF) thermal spraying technology in this paper. Cavitation erosion behavior and mechanism of the coating was studied through the analysis of curves for cavitation erosion resistance versus time and the observation of eroded particles, with the AISI 321 steel as a reference. It was found that the Fe-based coating had better cavitation erosion resistance than the AISI 321 steel, and exhibited obvious periodic failure behavior in the cavitation erosion process. Besides, the crystallization of the amorphous phase under the effect of shock wave was observed. The cavitation erosion mathematic model of the coating was also established. The model indicated that the cavitation erosion resistance of the coating was related to the grain size and the fracture energy per unit area of the coating. Small grain size and high fracture energy per unit area were benefit to improve the cavitation erosion resistance of the Fe-based coating.

Effects of Crystallization on the Corrosion Resistance of Arc-Sprayed FeBSiNb Coatings

Abstract: FeBSiNb coatings with a primarily glassy structure were prepared by arc spray processing. The as-sprayed coating was devitrified at various annealing temperatures to form different portions of crystalline phase. The effect of crystallization on the corrosion resistance of the coatings was systematically studied by potentiodynamic polarization and electrochemical impedance spectroscopy analysis in 3.5 wt.% NaCl solution. The results indicate that the as-sprayed coatings exhibit a superior corrosion resistance to the crystallized coatings with high polarization resistance, and the corrosion resistance of the coating deteriorates with the increase in the amount of crystalline phase. The corrosion resistance of both as-sprayed and devitrified coatings is explained in terms of chemical and structural characteristics of the alloys.

Ultrasonic cavitation erosion behaviors of high-velocity oxygen-fuel (HVOF) sprayed AlCoCrFeNi high-entropy alloy coating in different solutions

Abstract: In this study, an AlCoCrFeNi high-entropy alloy (HEA) coating was fabricated by HVOF spraying process. The HEA coating was consisted of the BCC phase (Al-rich phase) and FCC phase (Al-poor phase). The BCC phase was main phase. The mechanical performances and corrosion resistances of the coating and 06Cr13Ni5Mo martensitic stainless steel were analyzed in detail. The cavitation erosion behaviors and mechanisms of the HEA coating and 06Cr13Ni5Mo steel were investigated in distilled water and 3.5 wt% NaCl solution. The effects of microstructures, mechanical properties and corrosion properties on cavitation erosion mechanisms were discussed through the observation of eroded surface morphologies. The results showed that the cavitation erosion resistance of the AlCoCrFeNi coating was about 3.5 times that of the 06Cr13Ni5Mo steel in both solutions. In the 3.5 wt% NaCl solution, corrosion damage aggravated cavitation erosion damage, although the enhancement effect of corrosion on cavitation was limited. The corrosion environment did not change the cavitation erosion mechanisms of the two materials. The cavitation erosion mechanism of the HEA coating was lamellar spalling caused by the extension of the interlaminar cracks. Due to the lower plastic deformation resistance, the cavitation erosion mechanism of the 06Cr13Ni5Mo steel was material spalling caused by plastic deformation and fatigue fracture.

A review on laser cladding of high-entropy alloys, their recent trends and potential applications

Abstract: High-Entropy Alloys (HEAs) are a promising class of metallic materials that have allured the world of material science and engineering. These intriguing materials are proving their worth in the coatings for severe ambient and demanding conditions. Laser cladding (LC) is a non-linear complex, multidisciplinary and modern technology applied for surface modification. Nobler properties of HEAs as compared to traditional alloys permitted the research community to explore Laser-Cladded High-Entropy Alloy Coatings (LC-HEACs). Here, this article provides a review and recent trends of LC-HEACs, aiming to address the use of LC technology for HEA materials, the influence of process parameters on the geometric and metallurgical characteristics of the LC-HEACs. Common defects not limited to microcracks and residual stresses, and techniques to improve the quality of the LC-HEACs are elucidated. Furthermore, thermo-kinetics effect, thermomechanical behavior, microstructural evolution, and strengthening mechanisms are illustrated for a better understanding of laser-material interaction. The potential applications of the LC-HEACs are outlined considering wear, corrosion, erosion, and oxidation resistance and their corresponding substrates. The article also highlights the research gaps, current trends, and possible future directions in the context of critical challenges that need to be catered, before the actual implementation of LC-HEACs in industries. Owing to the variety of element constitution for HEAs design as well as excellent mechanical and functional properties, LC-HEACs will blossom in the years to come.

Microstructure and cavitation erosion behavior of HVOF sprayed ceramic-metal composite coatings for application in hydro-turbines

Abstract: Cavitation erosion commonly occurs in hydro-turbine blades and has been a crucial issue for operation of hydro-turbines. In this paper, high-velocity oxygen-fuel (HVOF) spraying was applied to produce Cr3C2–NiCr and WC-CoCr ceramic-metal coatings. The microstructure and the relationship between the flow velocity and cavitation erosion behavior of the coatings were evaluated, and their cavitation erosion mechanisms at different flow velocities were discussed. Experimental results showed that the WC-CoCr coating exhibited slightly lower porosity and significantly higher microhardness as compared to the Cr3C2–NiCr coating. Both ceramic-metal coatings were combined well with the steel substrate and showed an increase in the volume loss rates with increasing flow velocity. The volume loss rates for the WC-CoCr coatings were lower than that of the Cr3C2–NiCr coatings at each flow velocity. The critical flow velocity of the Cr3C2–NiCr coating was in the region of 33.5–41.9 m s−1. The cavitation erosion process of the Cr3C2–NiCr coatings mainly included removal of chromium carbide particles, coalescence of the craters and brittle detachment of the coating, while the failure mechanism of the WC-CoCr coatings was erosion of the binder phase at 23.4 m s−1, cavitation pits interlinking at 33.5 m s−1, and detachment of the WC particles at 41.9 m s−1.

Cavitation erosion characteristics at various flow velocities in NaCl medium of carbide-based cermet coatings prepared by HVOF spraying

Abstract: This study aims to investigate the correlation between flow velocity and cavitation erosion (CE) characteristics of high-velocity oxygen-fuel (HVOF) sprayed Cr3C2-NiCr (CN) and WC-Cr3C2-Ni (WCN) coatings in 3.5 wt% NaCl medium, except for the microstructures, mechanical properties and electrochemical behaviors. In comparison with the CN coating, the WCN coating shows higher values of elastic modulus (E), hardness (H), H/E and H3/E2 as well as lower porosity, resulting in lower volume loss rate (VLR) and enhanced CE resistance in NaCl medium at each value of flow velocity. The VLR values of both coatings increase as the flow velocity increases. The change of the CE progresses in NaCl medium of the CN coating is the formation of cavitation pinholes, pits, craters and oxidation films coupled with the exfoliation of chromium carbide particles when the flow velocity is 23.4 and 33.5 m s−1 as well as the brittle fracture structure with layers delamination accompanied by the oxidation films when the flow velocity is 41.9 m s−1. In a wide flow velocity range, the formation of cavitation pinholes, pits and micro-cracks along with the oxidation films are addressed as the dominant CE mechanism in NaCl medium of the WCN coating.

Optimization of mechanical and corrosion properties of plasma sprayed low-chromium containing Fe-based amorphous/nanocrystalline composite coating

Abstract: In this work, iron (Fe)-based amorphous/nanocrystalline composite coatings were synthesized using low-chromium containing amorphous powder (Fe73Cr2Si11B11C3, at. %) via atmospheric plasma spraying (APS) at different plasma spraying parameters. Coatings were deposited with 2 and 3 numbers of torch pass to get different coating thickness, along with the plasma power range was varied from 25 kW to 35 kW to alter the degree of powder melting. Microstructural studies demonstrated that porosity content and fraction of crystalline phase formation in the coatings were highly sensitive to spraying parameters. Increase in both the plasma power and coating thickness led to reduction in the porosity content and higher devitrification. Nanohardness of the coatings increased at elevated plasma power which was ascribed to the formation of denser coatings and precipitation of nano-sized Fe-borides, and therefore wear resistance of the coatings also improved. However, decrease in corrosion resistance was observed in the coatings deposited at the highest spraying power of 35 kW. Corrosion resistance improved with increasing coating thickness because of reduction in pore content, while formation of larger grains in thicker coatings caused decrease in nanohardness. Spraying power of 30 kW with three numbers of torch passes was found to be the optimum spraying parameters, and coating deposited at these parameters showed nanohardness value of 11 GPa, wear resistance coefficient of 49.9 × 1011 Pa and corrosion current density of 16 μA/cm2. This indicates that Fe-based composite coating synthesized at optimized parameters could be a good alternative for industrial applications due to higher wear and corrosion resistance.

A Comparative Study on Ni-Based Coatings Prepared by HVAF, HVOF, and APS Methods for Corrosion Protection Applications

Abstract: Selection of the thermal spray process is the most important step toward a proper coating solution for a given application as important coating characteristics such as adhesion and microstructure are highly dependent on it. In the present work, a process-microstructure-properties-performance correlation study was performed in order to figure out the main characteristics and corrosion performance of the coatings produced by different thermal spray techniques such as high-velocity air fuel (HVAF), high-velocity oxy fuel (HVOF), and atmospheric plasma spraying (APS). Previously optimized HVOF and APS process parameters were used to deposit Ni, NiCr, and NiAl coatings and compare with HVAF-sprayed coatings with randomly selected process parameters. As the HVAF process presented the best coating characteristics and corrosion behavior, few process parameters such as feed rate and standoff distance (SoD) were investigated to systematically optimize the HVAF coatings in terms of low porosity and high corrosion resistance. The Ni and NiAl coatings with lower porosity and better corrosion behavior were obtained at an average SoD of 300 mm and feed rate of 150 g/min. The NiCr coating sprayed at a SoD of 250 mm and feed rate of 75 g/min showed the highest corrosion resistance among all investigated samples.