Chemical influence of different pH-values on ductile mode processing through ultra-precision diamond turning

Abstract

One request for the optical machining of hart and brittle materials such as glass or tungsten carbide is not to exceed the critical depth of cut characterized by the transition point from ductile to brittle material removal. Bifano et all. demonstrated the possibility to apply ductile cutting mechanism while machining hart and brittle materials by the use of ultra precision machines which enable highest precision in feed control and indentation depths. Based on the investigations a formula relating the material specific properties Youngs-Modulus E, material hardness H and fracture toughness KC was developed [1]. For this, the influence of the cutting conditions and the process environment were not taken into account. But previous investigations have shown a high influence of the cutting fluid while machining binderless nanocrystalline tungsten carbide through ultraprecision diamond turning [2]. Concluding, calculating the transitions point by using the formula shows insufficiently results and cannot be used for setting up a stable and efficient process. To adjust the formula and to allow a better prediction of the cutting process, further investigations are necessary. This paper focuses in particular on the influence of water with different pH-values (acidic, neutral and alkaline) on the transition point for some brittle materials, binderless tungsten carbide and two different kinds of glass. Basic ruling experiments with a steadily increasing depth of cut have been performed. Measurements by white light interferometry have been done to analyze the influence on the cutting performance of mono crystal diamonds. As a result, a deeper understanding of the chemical influence on the mechanical process of diamond machining is created.