| FENG Mao,LIAN Ying,LI Yang,WU Yapeng.Research Progress in Cavitation Erosion Behavior and Affecting Factors of WC-Co-Cr Coatings Sprayed by HVOF[J],53(17):1-16, 111 |
| Research Progress in Cavitation Erosion Behavior and Affecting Factors of WC-Co-Cr Coatings Sprayed by HVOF |
| Received:November 07, 2023 Revised:January 02, 2024 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.17.001 |
| KeyWord:HVOF WC-Co-Cr coating cavitation erosion affecting factor |
| Author | Institution |
| FENG Mao |
School of Mechanical and Equipment Engineering, Hebei University of Engineering, Hebei Handan , China |
| LIAN Ying |
School of Mechanical and Equipment Engineering, Hebei University of Engineering, Hebei Handan , China |
| LI Yang |
School of Mechanical and Equipment Engineering, Hebei University of Engineering, Hebei Handan , China;Key Laboratory of Intelligent Industrial Equipment Technology of Hebei Province, Hebei Handan , China |
| WU Yapeng |
School of Mechanical and Equipment Engineering, Hebei University of Engineering, Hebei Handan , China |
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| Abstract: |
| Due to their excellent performances, the WC-Co-Cr coatings sprayed by HVOF (high-velocity oxy-fuel) are always employed to protect the flow passage components from cavitation erosion damage. The work aims to summarize the cavitation erosion mechanism, the preparation process of the coating, and the factors affecting the cavitation erosion behavior of the coating. Furthermore, from the perspective of the feedstock powder, spraying process, working conditions, mechanical property, cavitation erosion mechanism, and the comparison with other coatings, the achievements of cavitation erosion research on WC-Co-Cr coatings prepared by HVOF in China and abroad are summarized and analyzed deeply. The factors affecting the cavitation erosion performance of HVOF sprayed WC-Co-Cr coating can be classified into internal and external factors. The external factors, namely working conditions, involve cavitation time and medium (medium temperature, medium corrosion, medium flow velocity, solid particle, etc.), and the internal factors are concerned with the mechanical properties and microstructure of the coating. Moreover, the mechanical property mainly refers to the microhardness, cohesive strength, fracture toughness, and residual stress, and the microstructure is primarily related to the element distribution, phase composition, porosity, and lamellar structure. Nevertheless, the mechanical properties and microstructure are determined by the feedstock powder, spraying parameter, post-spaying treatment, etc. Moreover, the spraying powder factor includes WC particle scale, Cr element, rare earth element, etc., the spraying parameter contains fuel type, combustion-supporting gas, and others (spraying distance, powder feeding amount, spraying method, etc.), and the post-treatment factor involves sealing, grinding and polishing treatment. The WC particle size can affect the melting degree of the powder in the spraying process and the impact deformation degree of the power in the depositing process, affecting the microstructure, property, and anti-cavitation erosion of the as-sprayed coating. The protective film induced by the Cr element can inhibit the corrosion of the coating and reduce the porosity of the coating by sealing the pores. Appropriate addition of rare earth content can refine WC grain, reduce the porosity, and improve the microhardness and fracture toughness of the coating. Due to the higher particle flying velocity and lower spraying temperature, which are caused by the use of compressed air instead of pure oxygen, the microstructure, property, and anti-cavitation erosion of the coating sprayed by HVAF generally differ from those of the coating deposited by HVOF. Compared with HVOLF (high-velocity oxygen liquid fuel), the equipment for HVOGF (high-velocity oxygen gas fuel) is simple, economical, and convenient for field application, but its spraying temperature is high, and the particle flying velocity is low, which can result in high porosity and serious WC decarbonization. The cavitation erosion rate versus the time curve of HVOF sprayed WC-Co-Cr coating does not possess the typical stages (incubation period, acceleration period, stability period, and deceleration period), which are always present in the cavitation erosion behavior of the bulk metallic material. In corrosive medium under cavitation conditions, the damage of the coating is the joint result of pure cavitation erosion effect, corrosion-induced cavitation erosion effect, pure corrosion effect, and cavitation erosion-induced corrosion effect. The properties (porosity, microhardness, fracture toughness, bonding strength, residual stress, etc.) play significant roles in the cavitation erosion resistance of the coating. As to the cavitation erosion damage mechanism, the cavitation crack in the coating is mainly initiated at the pore and propagated along the carbide-binder interface and lamella boundary. The cavitation erosion behavior of HVOF-sprayed WC-Co-Cr coating has been studied by some researchers. Nevertheless, further detailed investigations are still needed since the complex relationship between the microstructure, mechanical property, working conditions, and the cavitation erosion behavior of the coating has yet to be fully understood. Based on the existing problems, the cavitation erosion research trend of the coating is proposed. The WC-Co-Cr coating sprayed by HVOF possesses outstanding cavitation erosion resistance, and the research on the cavitation erosion behavior of the coating will be helpful in providing a theoretical basis for the coating optimization design and cavitation erosion failure prevention in engineering applications. |
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