Solid State Phenomena Vol. 378

Abstract: The paper presents an optimization approach for enhancing the hardness and adhesion of Al₂O₃-40%TiO₂ coatings produced by High-Velocity Oxi-Fuel (HVOF) thermal spraying, aimed at their application in protecting components subjected to aggressive environments and severe mechanical stresses [1-4]. Through an experimental factorial program, key parameters of the HVOF process such as fuel flow rate, oxygen flow rate, spray distance, and powder feed rate were investigated to identify optimal conditions leading to improved mechanical performance of the deposited layers. Vickers hardness and tensile adhesion tests were utilized to evaluate the properties of the coatings. The results indicated that increasing the fuel and oxygen flow rates, coupled with reducing the spray distance, significantly increased the hardness of the coatings, achieving values up to 244 HV5. Moreover, optimizing these parameters maximized the coating-substrate adhesion, reaching values exceeding 30 MPa. Microstructural analysis using scanning electron microscopy (SEM) revealed that optimized HVOF parameters generated dense layers with low porosity and enhanced adhesion at the layer-substrate interface, thereby explaining the superior mechanical behaviors of the coatings. These findings demonstrate the capability of HVOF technology to produce Al₂O₃-40%TiO₂ layers with optimal mechanical properties, essential for applications requiring resistance to wear, impact, and corrosive environments [5-7].