Analysis of the Influence of Ultrasonic Vibrations on the Microstructure of Stainless Steel During Direct Laser Deposition

A combined method of direct laser deposition with ultrasonic treatment was investigated. An experimental test rig was developed to validate the method, ensuring immobilization of the substrate and protecting the Langevin ultrasonic transducer from overheating. To perform a quantitative analysis of the effect of ultrasonic treatment on the microstructure of stainless steel, a program was developed to determine the size distribution of columnar dendrites from optical images. Comparative analysis of the results showed that ultrasonic vibrations lead to refinement of the columnar dendritic structure. The average size of the columnar dendrites decreased by between 22.1 and 43.3% for different zones of the specimen’s cross section. Analysis of the standard deviation indicated that dendrite size values are more tightly clustered around the mean, which points to a more uniformly distributed metal structure in experiments with ultrasonic treatment. It is concluded that the observed refinement may be caused by acoustic streaming and cavitation effects.