Sheng Hong

Bio: Sheng Hong is an academic researcher from Hohai University. The author has contributed to research in topics: Coating & Thermal spraying. The author has an hindex of 21, co-authored 69 publications receiving 1092 citations.

Microstructure and cavitation–silt erosion behavior of high-velocity oxygen–fuel (HVOF) sprayed Cr3C2–NiCr coating

Abstract: In this paper, a Cr3C2–NiCr coating was prepared by means of high-velocity oxygen–fuel (HVOF) thermal spraying process and analyzed with regard to their cavitation–silt erosion (CSE) behavior under different sediment concentration conditions. It is found that Cr3C2, Cr7C3, Cr2O3 and (Cr, Ni) phases are obtained in the coating. The binder matrix contains amorphous phase and nanocrystalline grains. The crystallization temperature of the amorphous phase is about 559 °C. The coating exhibits low porosity and high microhardness. After being eroded for 20 h, the CSE mass loss of the coating in 40 kg·m− 3 is 1.15 and 1.23 times to that in 20 kg·m− 3 and in 0 kg·m− 3, respectively. Due to increase in interaction area of sand particles with specimen, the CSE rate is found to increase progressively as sediment concentration increases. Signatures of lips, craters, microcutting, cracks and micropores are observed on the eroded surface of the coating. The CSE mechanism for the coating is a composite ductile and brittle mode.

Fabrication and Characterization of Thermal-Sprayed Fe-Based Amorphous/Nanocrystalline Composite Coatings: An Overview

Abstract: This review focuses on the recent development of iron (Fe)-based amorphous/nanocrystalline composite coatings, which have attracted much attention due to their attractive combination of high hardness/strength, elevated abrasive wear resistance, and enhanced corrosion resistance. Accompanying the advancements in various thermal spray technologies, industrial application fields of Fe-based amorphous/nanocrystalline composite coatings are becoming more diverse. In the main part, the typical empirical rules for the design of amorphous alloys with high glass-forming ability are generalized and discussed at first. Then various thermal spray technologies for the fabrication of Fe-based amorphous/nanocrystalline composite coatings, such as high velocity oxygen/air spray (HVOF/HVAF), air plasma spray (APS), low-pressure plasma spray (LPPS), high-energy plasma spray (HPS), and high velocity arc spray (HVAS) processes, are introduced. The microstructures, hardness, wear resistance, and corrosion resistance of Fe-based amorphous/nanocrystalline composite coatings formed using these thermal spray technologies are reviewed and compared. Finally, the existing challenges and future prospects are proposed.

Microstructure and cavitation erosion behavior of WC–Co–Cr coating on 1Cr18Ni9Ti stainless steel by HVOF thermal spraying

Abstract: A WC–Co–Cr coating was deposited by a high velocity oxy-fuel thermal spray (HVOF) onto a 1Cr18Ni9Ti stainless steel substrate to increase its cavitation erosion resistance. After the HVOF process, it was revealed that the amorphous phase, nanocrystalline grains (Co–Cr) and several kinds of carbides, including Co3W3C, Co6W6C, WC, Cr23C6, and Cr3C2 were present in the coating. The hardness of the coating was improved to be 11.3 GPa, about 6 times higher than that of the stainless steel substrate, 1.8 GPa. Due to the presence of those new phases in the as-sprayed coating and its higher hardness, the cavitation erosion mass loss eroded for 30 h was only 64% that of the stainless steel substrate. The microstructural analysis of the coating after the cavitation erosion tests indicated that most of the corruptions took place at the interface between the un-melted or half-melted particles and the matrix (Co–Cr), the edge of the pores in the coating, and the boundary of the twin and the grain in the stainless steel 1Cr18Ni9Ti.

High-velocity oxygen-fuel spray parameter optimization of nanostructured WC–10Co–4Cr coatings and sliding wear behavior of the optimized coating

Abstract: In this paper, the Taguchi method was employed to optimize the spray parameters (spray distance, oxygen flow and kerosene flow) to achieve the highest hardness and, in turn, the best wear resistance of the high-velocity oxygen-fuel (HVOF) sprayed nanostructured WC–10Co–4Cr coating by investigating the correlation between the spray parameters and the hardness. The important sequence of spray parameters on the hardness of the coatings is kerosene flow > oxygen flow > spray distance, and the kerosene flow is the only significant factor. The optimal spray parameter (OSP) for the coating is obtained by optimizing hardness (330 mm for the spray distance, 2000 scfh for the oxygen flow and 6.0 gph for the kerosene flow). The coating deposited under the OSP with low porosity and high microhardness consists predominately of WC and a certain amount of W2C phases. The coating deposited under the OSP exhibits better wear resistance compared with the cold work die steel Cr12MoV. The material removal of the coating is the extrusion of the ductile Co–Cr matrix followed by the crack and the removal of the hard WC particles.

Synergistic effect of ultrasonic cavitation erosion and corrosion of WC-CoCr and FeCrSiBMn coatings prepared by HVOF spraying

Abstract: The high-velocity oxygen-fuel (HVOF) spraying process was used to fabricate conventional WC-10Co-4Cr coatings and FeCrSiBMn amorphous/nanocrystalline coatings. The synergistic effect of cavitation erosion and corrosion of both coatings was investigated. The results showed that the WC-10Co-4Cr coating had better cavitation erosion-corrosion resistance than the FeCrSiBMn coating in 3.5 wt.% NaCl solution. After eroded for 30 h, the volume loss rate of the WC-10Co-4Cr coating was about 2/5 that of the FeCrSiBMn coating. In the total cumulative volume loss rate under cavitation erosion-corrosion condition, the pure cavitation erosion played a key role for both coatings, and the total contribution of pure corrosion and erosion-induced corrosion of the WC-10Co-4Cr coating was larger than that of the FeCrSiBMn coating. Mechanical effect was the main factor for cavitation erosion-corrosion behavior of both coatings.

Fe-based bulk metallic glasses: Glass formation, fabrication, properties and applications

Abstract: The invention of bulk metallic glasses has stimulated extensive interest, due to their possible technological applications in a variety of industrial fields and their scientific importance in understanding related condensed matter physics. Among all types of BMGs, Fe-based BMGs are a unique yet important family due to their high mechanical strength, good thermal stability, strong corrosion resistance, excellent soft magnetic properties, and relatively low production costs. Since the first synthesis of the Fe-Al-Ga-P-C-B BMG reported in 1995, a vast body of literature regarding Fe-based BMGs has been published. However, until now, a full and systematic description of the development status and future prospects of Fe-based BMGs has been missing. Therefore, this article presents the research development and achievements of Fe-based BMGs in the past few decades, including their preparation, glass-forming ability, crystallization characteristics, mechanical properties, corrosion behaviors, soft and hard magnetic properties, and industrial applications. In addition, future developments of Fe-based BMGs are also proposed.

Corrosion resistance of Fe-Cr-based amorphous alloys: An overview

Abstract: The present article focuses on the current status of research and development concerning corrosion resistance of Fe-Cr-based amorphous alloys and gives suggestions for further investigations aimed at improving the performance of these alloys and recommendations of possible new applications. These materials, which are usually obtained either as glassy bulk material or in coating and ribbon form, show high corrosion resistance and high wear resistance and are also relatively inexpensive compared to other amorphous metallic alloys. These characteristics can lead to promising applications of these alloys in which corrosion resistance and erosion-corrosion resistance are important. This review presents the results obtained in recent years, including the effect of amorphous structure, partial crystallization and composition on corrosion resistance, as well as applications of these alloys. Although advances have been made in studies concerning Fe-Cr-based amorphous alloys, there is an important limitation in terms of using them, which is the issue related to the high Mo content needed to achieve sufficient glass-forming ability and high corrosion resistance, which significantly increases the cost of these alloys. Therefore, the cost/benefit relation of these alloys needs to be improved by studying the effect of composition and structure on corrosion resistance and finding new applications of these alloys. Based on this literature review, possible applications and further investigations of these alloys are suggested.

Recent Progress on Wear-Resistant Materials: Designs, Properties, and Applications.

Abstract: There has been tremendous interest in the development of different innovative wear-resistant materials, which can help to reduce energy losses resulted from friction and wear by ≈40% over the next 10-15 years. This paper provides a comprehensive review of the recent progress on designs, properties, and applications of wear-resistant materials, starting with an introduction of various advanced technologies for the fabrication of wear-resistant materials and anti-wear structures with their wear mechanisms. Typical strategies of surface engineering and matrix strengthening for the development of wear-resistant materials are then analyzed, focusing on the development of coatings, surface texturing, surface hardening, architecture, and the exploration of matrix compositions, microstructures, and reinforcements. Afterward, the relationship between the wear resistance of a material and its intrinsic properties including hardness, stiffness, strength, and cyclic plasticity is discussed with underlying mechanisms, such as the lattice distortion effect, bonding strength effect, grain size effect, precipitation effect, grain boundary effect, dislocation or twinning effect. A wide range of fundamental applications, specifically in aerospace components, automobile parts, wind turbines, micro-/nano-electromechanical systems, atomic force microscopes, and biomedical devices are highlighted. This review is concluded with prospects on challenges and future directions in this critical field.

Pitting initiation in Fe-based amorphous coatings

Abstract: Amorphous metallic coatings, especially Fe-based amorphous coatings, are thought to have promising potential for industrial applications in aggressive environments due to their excellent corrosion resistance. The intersplat regions in the coating have been suspected to be the preferential locations for pitting initiation. However, no direct evidence has been provided so far for pitting initiation at the regions. In this study, the pitting behavior of a high-velocity oxy-fuel thermally sprayed Fe-based amorphous coating of composition Fe48Cr15Mo14C15B6Y2 in a 6 M NaCl solution was studied in detail via high-resolution transmission electron microscopy (TEM) coupled with nanobeam energy-dispersive X-ray spectroscopy (EDX). It was found that pitting was always initiated in a narrow region ∼100 nm wide near the intersplat regions, but not exactly at the expected regions. Nanobeam EDX indicated that a Cr-depleted zone exists near the intersplat due to the oxidation effect. More interestingly, pitting was found to occur only on one side although Cr depletion is equal on the two sides of the intersplat. This can be well explained in terms of the galvanic effect between the Cr-depleted zone and the Cr-rich intersplat regions. The findings provide a new insight into the corrosion mechanism of Fe-based amorphous coatings.