Мікроструктура та характеристики нікелевих покриттів, отриманих на титановому сплаві холодним газодинамічним напилюванням

The subject of this research is the dependence of the influence of cold spraying regimes on coating characteristics. This paper aims to approve the recommended cold-spraying regimes, which operate at an air pressure of up to 1.0 MPa, and to determine the main characteristics of coatings (microstructure, adhesion strength and microhardness) from Ni+Al2O3 powder on titanium alloy. The task: to investigate the formation of a complex of coating characteristics (microstructure, adhesion strength and microhardness) under selected operating regimes of the cold spraying process. Research methods. The study of the features of the microstructure of coatings and the contact surface of the coating with the substrate was performed by optical microscopy methods on prepared transverse microsections of samples with coatings. The study of the adhesion strength and microhardness of coatings was conducted by engineering mechanics methods using standard methods for evaluating thermal spray coatings. Results. The average values of the adhesion strength of Ni+Al2O3 powder coatings on VT9 titanium alloy were 30.2 MPa. Following the requirements for the minimum required values of the adhesion strength of cold spray coatings (15 MPa), the obtained results ensure their machinability by cutting to achieve the specified parameters of accuracy and roughness of the coated surface. The microhardness values of Ni+Al2O3 powder coatings on VT9 titanium alloy were obtained along the coating thickness. The average microhardness values were from 190 HV to 290 HV, exceeding the required 180 HV. The microstructure of Ni+Al2O3 powder coatings on VT9 titanium alloy was investigated. No through porosity, defects, or delamination of the coating from the surface were detected. Conclusions. The results of the conducted experimental studies confirmed the possibility of using the proposed operating regimes of the cold spraying process, which is performed with a working air pressure of up to 1.0 MPa, for applying protective and restorative coatings of Ni+Al2O3 powder on parts made of titanium alloys while ensuring the specified requirements for qualitative and quantitative characteristics.