Coating of Co–Cr–Mo alloy for surgical implants by centrifugal spray: Preliminary evaluation

A new industrial method for coating metallic prostheses is described. This technique involves the atomization of a Co–Cr–Mo (ASTM F75) alloy ingot by means of a nitrogen plasma discharge onto the alloy electrode rotating at 360 r.p.s. Centrifugal forces cause the melted zone to generate spherical droplets of diameter varying 20 and 200 μm. The droplets are sputtered onto the metallic substrate in successive layers, forming a 3-D porous structure with a rough surface (CLA (124 ± 82) μm and depth of 1000–1500 μm). The process allows forming a microstructure composed of a network of fine carbide lamellae (of about 0.1–1 μm thick) in an austenitic cobalt solid solution matrix. The solidification structures and phase distribution were studied by scanning electron microscopy (SEM) equipped with an energy-dispersive spectrometer, X-ray diffraction and electron probe microanalysis. The process is feasible and the obtained microstructures may favour the mechanical anchorage of cementless joint prostheses.