Utilising of water hammer effect for surface roughening of Ti6Al4V

Abstract

There are many technological ways to activate biocompatible surfaces, but in some cases, there are not reliable for elderly patients. It has been found that surfaces created using pulsating water jets have a structure similar to trabecular bone struc tures. Such a similar shape to the endoprosthesis stems would enable faster fxation. The paper presents a novel way of utiliz ing the water hammer efect caused by forced multiple droplet impingement with a spatial frequency of 40,000 i/s on Ti6Al4V titanium alloy surface under diferent technological conditions. The objective was to create a structured surface with desired values of surface profle parameters Ra and Rz to increase the possible potential for implant osseointegration, fxation and stability. Pulsating water jet was generated at pressures from 20 to 100 MPa using a circular nozzle with a diameter of 1.32 mm. Two diferent strategies of the jet trajectory, namely linear and cross-hatch strategy, were investigated. Results were compared with grit blasted followed by plasma spray-coated femoral stem for cementless total hip arthroplasty. It has been found that variation in the input parameters results in signifcant changes in the surface generated. Samples whose surfaces were generated using energy intensity lower than 5 KJ/mm2 and have surface roughness in the range Ra = 4 – 8 μm were selected for surface topography and morphology analysis along with the commercial femoral stem. SEM analysis revealed the absence of foreign contamination and steeper surface heights on pulsating water jet treated samples compared to standard femoral prosthetic. The cross-section images showed the presence of sub-surface voids and craters of diferent sizes due to the jet's action. Surface topology is similar to trabecular shape. This indicates that roughening the surface increases the surface area and thus has potential bone tissue ingrowth during osseointegration.