Fundamental mechanisms in orthogonal cutting of medical grade cobalt chromium alloy (ASTM F75)

Following a brief overview of physical and mechanical properties of this class of Co-Cr-Mo alloys, the results of a full factorial, orthogonal cutting experiment are presented. This involved measurement of force components (Ft and Ff) as a function of the undeformed chip thickness (h) and cutting speed (vc) which were varied over ranges from 20 to 140 μm and 20 to 60 m/min respectively. The results demonstrated an expected linear increase in force components with h at speeds of 20 and 60 m/min. However, at the intermediate speed of 40 m/min, there was a transition between about 60 and 80 μm indicating a discontinuous rather than continuous effect of speed. The results also enabled determination of the cutting force coefficients Ktc, Kte, Kfc and Kfe, as well as ki1,0.1 and mi0.1 of the Kienzle equations. These relations will enable macro-mechanic modelling of more complex cutting operations, such as milling, in the future.