Influence of the oscillating systems inclination angle on the surface properties of steel 45 during ultrasonic surface plastic deformation

Introduction. Among the methods of modifying the surfaces of metal products to change the physical-mechanical and geometric properties of the surface layer, surface plastic deformation (SPD) methods are the most prevalent. Using ultrasound to enhance the efficiency of deformation processes allows for increase in microhardness and reduction in roughness compared to rolling and smoothing. The greatest technological challenges are caused by ultrasonic surface plastic deformation of curved surfaces, including those obtained by additive technologies. Given that most ultrasonic SPD methods are based on the longitudinal nature of vibrations, to ensure uniform processing of curved surfaces, the tool axis should be oriented at a specific angle relative to any point on the surface being processed. In this regard, the purpose of the work is to study the effect of the oscillating system inclination angle on the surface properties of steel 45 during ultrasonic surface plastic deformation. This study examines steel 45 samples subjected to ultrasonic SPD at various oscillating system inclination angles: 90°, 75°, 60°, and 45°. Methods. The research methods included metallographic studies of the surface layer microstructure of the samples, measurement of its microhardness and roughness, as well as comparative wear tests. Results and discussion. Ultrasonic surface deformation, at any of the considered tool inclination angles α, creates a hardened layer – from 30 µm at α = 45° to 350 µm at α = 90 °. In this case, the microhardness increases to 240 HV at α = 45°. Furthermore, at any α, there is a significant decrease in roughness. For example, altitude parameters are reduced by more than 8 times. The best results were achieved at α = 60°. The wear test results indicated a substantial reduction in weight loss due to wear following ultrasonic processing. The most significant decrease in wear (more than twofold) was observed at an inclination angle of α = 90°.