Determination of residual stress within complex-shaped coarse-grained cobalt-chromium biomedical castings

Cast ASTM F75 femoral knee implant components distort during manufacture due to residual stress re-distribution or inducement. These castings pose a number of challenges for residual stress determination methods; they have a complex geometry, their microstructure is inhomogeneous, they work-harden rapidly and they have a coarse, elastically anisotropic grain structure. The contour method is anticipated to be the most promising residual stress determination technique. X-ray diffraction is feasible for components which have experienced plastic deformation on their surface which results in refined diffracting domains. Centre-hole drilling is feasible, but the influence of stress induced from drilling and the effect of coarse grain structure is unknown. Neutron diffraction is challenging also due to a coarse grain structure and difficult nuclear material properties.