Effects on Microstructure and Material Properties for TiNiCo Shape Memory Alloy

Wire spark discharge machining of TiNiCo alloys for bone staple applications is presented. A vacuum arc melting furnace was used to develop TiNiCo alloys with varied cobalt (Co) contents (1, 5 and 10 at. %). The investigation was performed to study the material removal rate (MRR) and surface quality (R a) as per the experimental design planned for an L33 array. The input process parameters were pulse-on/pulse-off duration servo voltage, wire speed and servo feed. From the responses on MRR and R a, optimal process conditions were identified using multiobjective gray analysis. It was concluded that the results obtained for different combinations of materials were in form of different combination of process parameters. The surface of bone staples (non-implanted) was characterized with respect to surface morphology, surface topography, recast layer thickness, microhardness and residual stresses. A smoother machined surface and compressive residual stresses were observed, which are favorable for improving the fatigue life of machined bone staples.