Fabrication of micro-channels on Co–Cr–Mo joints by micro-abrasive jet direct writing

Hectares of tribological micro-texture must be machined per year to reduce friction and wear in artificial articular joints. Productive and cost-effective tribo-texturing of freeform surfaces consisting of hard-to-machine materials is a current manufacturing challenge. This study evaluates the accuracy and productivity of micro abrasive jet machining when fabricating micro-channels on metal in a mask-less way. The influence of micro abrasive jet process parameters on micro-channel's geometry and fabrication speed is in focus in this study. We blast 27-μm alumina powder through Ø0.5 mm nozzle at Co-Cr-Mo substrate under 0.1 – 0.8 MPa of air pressure, 30° – 90° of nozzle angles and 0.5 – 3.5 mm of stand-off distance. Measurements show that the micro-channels can be as narrow as 110% of the nozzle diameter and have V-, U- or W-shaped bottom at the particular stand-off distance and air pressure. The fabrication speed of 550 μm × 5 μm channels (width × depth) reaches 260 mm/min and allows to texture the femoral head of a hip joint within several minutes using a single nozzle and a few grams of abrasives. Overall, the accuracy, productivity and cost-effectiveness of micro abrasive jet machining are highly suitable for tribological surface texturing of artificial joints.