Effect of Crystallographic Orientation on Ductile to Brittle Transition Using Nano-Scribing Method

Under normal machining conditions using traditional processes like turning and grinding, machining of ceramics is more of a crushing process rather than a metal cutting process. An advance in the precision engineering has led to the possibility and discovery of "ductile regime machining" of these materials. Earlier studies by various authors have shown wide variations in the critical depth of cut on the same crystallographic plane. Other authors have studied the effect of crystallographic orientation on the critical depth of cut in the same plane being machined by using single Point Diamond Turning and Fly cutting methods. The present study finds these variations in the critical depth of cut of Silicon (100) by conducting nano scribing experiments using Nano Indenter. The nano scribing was performed at 60 μm/s velocity and along 0 to 360°orientations at 15 degree interval. The critical depth of cut from Nano-indenter was further verified using Optical Profiler. It was found from the experimental results that the critical depth of cut varies with the scratch direction attributing to the crystal orientation. These results agree with the more qualitative results of many previous efforts.