Isotropic pyrolytic graphite is a kind of graphite material. Because of its excellent performance, it is gradually used in aero-engine turbine shaft seals. But this material is a kind of brittle material, and it wears seriously during the cutting process. Through analysis of the process of cutting this material with PCD insert, the main wear region and the wear pattern at different cutting time were obtained. Using the scanning electron microscopy to observe the wear regions, the wear mechanism of PCD was obtained. At the first stage of the wear mechanisms were mainly mechanical wear and abrasive wear, the main wear regions were rake face and the cutting edge. With the increase of cutting distance, about 32 min later, both the depth of the crater on the rake face and the depth of micro grooves on the flank face were increased. Abrasive wear on the cutting face and the micro grooves wear on the flank face were the main wear pattern at the stable wear stage. At rapid wear stage, cutting edge was transformed from micro chipping into tool tipping. This caused by erosion wear .Experimental results indicated that the wear pattern was typical mechanical wear, abrasive wear, cutting edge erosion wear and possible adhesive wear.

In order to improve machined surface quality and reduce the deformation, the residual stress involved in cutting titanium alloy was studied under different cutting speed and cutting depth by finite element simulation method. The results indicate that the increase of cutting speed and cutting depth are helpful to the surface residual compressive stress generating. However the increase of cutting speed also leads to the increase of surface residual tensile stress, the effect degree is relatively small. It is required to select higher cutting speed and smaller cutting depth to improve the surface stress state and reduce the unexpected distortion.

. In this study, the prediction models of thrust force, tool wear and torque in drilling nickel-based alloy GH536 are developed based genetic algorithm and drilling experiments. Tool wear value is used as constraint condition and maximum cutting efficiency as goal to optimize drilling process parameters. In addition, the relationship between tool life and cutting efficiency is analyzed by exploiting the tool wear prediction model. The results of the analysis show that under the condition of efficiency remains unchanged, the tool life can be increased by increasing drilling speed and appropriately reducing feed rate, these results are consistent with the optimized process parameters.