Drilling Performance of Novel Lightweight Carbon Specialty Graphites with Different Grain Sizes

Because of their excellent machinability, low density, and great thermal stability, specialty graphite materials are being utilized more and more in precision engineering applications. The impact of the graphite particle size on drilling performance under various cutting conditions, however, has not been well studied. The drilling performance of three specialty graphite materials with various grain sizes was examined in this study. While MSG30 and MSG46 have micrometer-sized grains with greater mechanical strength, the graphite substance labeled MSG215 has a coarse grain structure (0.9 mm). High speed steel and tungsten carbide drills were used in drilling experiments at three distinct feed rates and cutting speeds. Using Taguchi experimental design and analysis of variance, the effects of cutting settings and particle size on the thrust force were examined. Workpiece temperatures were monitored during drilling using embedded thermocouples, and the correlation between the temperature evolution at four distinct depth points and cutting parameters was assessed. The dimensional accuracy, tool wear, and surface roughness were additionally evaluated. The findings show that the drilling performance is significantly impacted by graphite grain size. In comparison to fine-grained materials, coarse-grained graphite generated thrust forces that were about 30% lower and surface roughness levels that were about 20% greater. The temperature increase during drilling was minimal, owing to the strong thermal conductivity of graphite, resulting in an average workpiece temperature of 35 °C and a rise of about 15 °C under dry cutting conditions. Tool wear and thermal loads were also reduced compared with those commonly seen in conventional engineering materials. In addition to offering useful advice for choosing appropriate cutting parameters and tool materials in precision graphite machining applications, the findings provide light on the microstructure-dependent drilling behavior of specialty graphite.