Improving the strength and corrosion resistance of 316L stainless steel for biomedical applications using cold spray

Stainless steel 316L mixed with cobalt chromium alloy L605 powders has been cold sprayed onto mild steel substrate. As spraying Co–Cr alone is difficult, three different proportions (by volume of Co–Cr, 25%, 33.3% and 50%) were used in this study. Analysis and characterization of sprayed depositions were performed through scanning electron microscopy, electron backscatter diffraction, microhardness, and tensile tests at room temperature. The porosity of the coating was low for both the 25% and 33.3% coating (about 0.9–1.5%). However, the 50% coating had a much poorer deposition rate leading to a much thinner coating using the same coating parameters; the porosity was much higher (about 4.5%). The ductility of the annealed 25% and 33.3% specimens reached approximately 20% and 18% respectively after annealing, but the 50% specimen was too thin to be tested. The corrosion behavior was evaluated using potentiodynamic polarization tests carried at Hank's solution as an electrolyte. It was found that corrosion resistances of the metal–metal mixture were higher than that of pure stainless steel.

► Using cold spray, coatings were produced from mixed SS and Co alloy powders.
► The heat treatments significantly lowered the coating porosity.
► Mixing SS powder with Co alloy shows higher strength compared to pure SS.
► The mixture was found to have lower corrosion rate in comparison to pure SS.
► No differences in the XRD peak patterns, confirming that there is no phase change.