Investigation of micro-blasting process on surface treatment of bio-implants

This project develops the capabilities of micro-abrasive jet machining (MAJM) for tailoring of surface integrity aspects responsible for osseointegration, adhesion strength, and lubrication of artificial articular joints (AAJs). The thesis starts with a literature review outlining six aspects of MAJM process, which must be addressed to enable surface functionalization of AAJs. In the second chapter, the project develops an analytical-numerical model of particle velocity field generated by micro-nozzle. The investigation highlights the effect of process parameters on the magnitude of particle velocity and the nature of its change. In the third chapter, an analytical solution is developed to describe the temperature rise during the impact of a single particle. Further, several numerical models and measurements are addressed for elaborating the steady-state thermal field during MAJM. The fourth chapter delivers a modified Hill’s ratio predicting lateral crack nucleation druing impact-induced fracturing and erosion rate of brittle materials. The following four chapters are application-focused. Fifth chapter is on the development of the bone/implant interfacial area. Six shape parameters of eight abrasive fractions and nine roughness parameters of Co-Cr-Mo surface eroded under sixteen blasting conditions are analysed. The fifth chapter improves adhesion strength and scratch-resistance of antibacterial coatings. The investigation contributes an extensive characterization of Ti-6Al-4V surface topography, microstructure, chemistry and wettability generated by milling, polishing, acid-etching and MAJM. The sixth and seventh chapters address the issue of poor tribological performance of AAJs, developing MAJM direct writing and a novel Tribo-blast surface texturing technique. This project delivers tools for managing particle velocity, jet kinetic energy, machining temperature, single crater size, surface roughness and erosion rate in MAJM. The bone/implant interfacial area, the scratch resistance of antibacterial coatings, and bearing index of the articular surface, all can be increased by a factor of two. The femoral head of a hip joint can be covered by micro-channels within a few minutes using only one nozzle and one gram of abrasives without the patterning masks or precision CNC actuators. Overall, the productivity and cost-effectiveness, makes MAJM a strong candidate for industrial implementation in the manufacturing chain of life-long AAJs.