2017 年 83 巻 8 号 p. 762-769
Diamond cutting tools show severe wear in turning of nickel, while electroless nickel deposits remarkably reduces the wear. To understand the wear mechanism in turning of nickel and electroless nickel, thermodynamics analyses of chemical reaction, erosion tests of diamond contacting with work materials and first principle analyses simulating wear process were carried out. The results show that the essential wear mechanism is the dissociation of carbon atoms on diamond surface due to the interaction with nickel atoms on work surface. Phosphorous addition reduces the dissociation because the interaction is suppressed. The lower cutting temperature in turning of electroless nickel than that of nickel also suppresses the interaction between the diamond and work surface. The easy dissociation of carbon atoms is also occurs with small activation energy due to the reaction with oxygen atoms adsorbed on work surface. However, the process causes a tool wear with very small rate in practical cutting, because the oxygen atoms are difficult to enter into the interface between tool and work material. The results suggest that the machinability of difficult-to-cut materials in diamond turning can be improved by some additional elements.
