The paper studies the influence of the oxygen-to-fuel ratio (O/F) on the microstructure, phase composition, porosity and hardness of quasi-crystalline (QC) Al59Cu25.5Fe12.5B3 coatings obtained by high-velocity oxygen-flame spraying (HVOF). It is established that changing the O/F significantly affects the coating characteristics.
Quasi-crystalline materials attract attention due to their unique combination of properties, such as high hardness, low friction coefficient and good corrosion resistance. HVOF is a promising method for applying QC coatings, allowing dense and uniform layers to be obtained.
Quasi-crystalline Al-Cu-Fe coatings were deposited by the HVOF (high-velocity oxygen-fuel) spraying method. The effect of the oxygen-to-fuel (O/F) ratio on the structure and porosity of the obtained coatings was studied using scanning electron microscopy, X-ray diffraction analysis and microhardness measurements. After heat treatment at 700°C for 5 minutes, the coating consisted almost entirely (~100%) of the quasi-crystalline phase. The results show that the O/F ratio affects the microstructure and properties of the coatings. The best combination of high hardness and low porosity is achieved at an O/F ratio slightly below 1.1, which corresponds to the theoretical value for complete combustion of kerosene.
Thermal spraying methods for depositing thick coatings are widely used in industry. Quasicrystalline coatings can be used as selective absorbers of solar radiation, thermal barriers, and as reinforcing particles for composite materials. The HVOF method has been successfully applied to obtain quasi-crystalline coatings on steel and cast iron. The quality of the coating deposited by the HVOF method depends on the process parameters, powder and substrate characteristics. The chemical composition and flame temperature affect the state of the particles, which affects the microstructure of the coating. Changing the O/F ratio allows you to control the deposition atmosphere. However, oxidizing flame can lead to oxidation of quasi-crystal particles. The effect of the chemical composition of the flame on the microstructure of aluminum-based quasi-crystals has not been sufficiently studied. In this paper, we studied the effect of different O/K ratios on the microstructure and properties of quasi-crystalline AlCuFeB coatings obtained by the HVOF method.
The coatings were applied to a steel substrate by the HVOF method using Al59Cu25.5Fe12.5B3 powder. The O/F ratio was varied while other process parameters were kept constant. The microstructure and phase composition were studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Hardness was measured by microindentation.
It is shown that increasing O/F leads to a decrease in porosity and an increase in the content of the KK phase in the coating. However, at excessively high O/F values, oxidation of the material and the formation of undesirable phases are observed. The best results in terms of microstructure and hardness were achieved with the optimal O/F ratio.
The oxygen-to-fuel ratio is an important parameter when applying QC coatings of Al59Cu25.5Fe12.5B3 by the HVOF method. Optimization of this parameter allows obtaining coatings with improved microstructural and mechanical properties.
Author: FRP Feitosa, RM Gomes, MMR Silva, SJG DeLima, JM Dubois
Institute: Federal University of Piauí, Faculty of Mechanical Engineering, University Campus Minister Petronio Portilla, Ininga, Teresina, CEP: 64.049-550, Brazil, Federal University of Paraiba, Faculty of Mechanical Engineering, Campus I, João Pessoa, Paraiba, CEP: 58.051-900, Brazil, Institut Jean L’Amour (UMR 7198 CNRS-University of Lorraine), Alley André Guinet, 2, BP50840, F-54011 Nancy, France