Surface modification of titanium alloy Ti6Al7Nb by high-frequency droplet impingement

Droplet erosion is commonly viewed as a negative consequence, causing damage to engineering structures. Recent research has shifted this perspective, harnessing the erosion process as a means to alter the surface properties of weld joints for stress alleviation or to modify the surface texture of biomaterials to enhance their biological potential. The practical applications of surfaces crafted through droplet erosion have been explored insufficiently, considering the research potential so far. The motivation of the present study is to compare surfaces created by the ultrasonic pulsating water jet (PWJ) technique with the surface of a grit-blasted Ti6Al7Nb femoral stem. The experiment employed two trajectory patterns (linear and interlaced perpendicular) and two different frequencies of the water droplet generation, i.e., f s = 20 and 40 kHz, promoting process diversity. The obtained erosion patterns were assessed using scanning electron microscopy observation. The textured surface characterization was conducted using areal height, hybrid, elemental, and functional roughness parameters , along with their isotropy . Findings indicate that alterations in the technological settings of the process lead to corresponding shifts in specific surface characteristics. Maintaining a roughness S a (areal arithmetic mean height) up to 10 μm, notable changes were detected in the height parameters S p (maximum areal peak height) being greater than S v (maximum areal valley depth) and the surface distribution S sk (skewness) and S ku (kurtosis). These outcomes suggest that tuning the ultrasonically modulated water jet technology parameters can fine-tune the textured surface to meet specific requirements for bioapplications . This comparative analysis demonstrates that the PWJ method can be an effective tool for active surface texturing, setting the stage for its broader practical application for medicine.