Collaborative Research: Multi-Scale Experiments and Modeling of Nanocrystalline Diamond Coatings for Dry Machining

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The objectives of this collaborative research award are to reliably grow and understand the behavior of nano-crystalline diamond coatings for cutting tools that will make dry machining economical. Tools of conventional sizes and novel micro-scale tools, as small as the width of a human hair, will be studied. The research approach involves growing extremely thin diamond coatings, measuring their friction properties, predicting their impact on cutting temperature, and evaluating them when dry machining an industrially-relevant aluminum alloy. The diamond growth process will be tailored to repeatably produce uniform diamond films, less than one-micrometer thick, with nanometer size grains, and strong adhesion to the tungsten carbide tool material. The friction, wear, and structural properties of the diamond films will be studied at from the nano- to macro-scale using atomic force microscopy, environmentally-controlled tribometry, spatially-resolved surface spectroscopy, and orthogonal machining experiments. This will determine the relationship between growth parameters and resulting coating properties. The cutting tool temperature reduction afforded by the low friction coefficient of the nano-crystalline diamond will be modeled. Dry machining performance of coated tools will be evaluated for drilling and micro end milling of a cast aluminum alloy with high silicon content that is used extensively in the transportation industry. This research will benefit society by addressing the major, unsolved industrial problem of metalworking fluids. Reducing or eliminating the use of metalworking fluids in dry machining of soft, abrasive metals, will simultaneously reduce the environmental impact and energy consumption of the manufacturing industry, resulting in improved economic competitiveness. Nano-crystalline diamond coatings are extremely promising because of their high hardness, low coefficient of friction, and low adhesion to workpiece material thus reducing wear, heat generation, and chip clogging, respectively. Further societal impact will result from training engineering students, recruiting and retaining students from underrepresented groups, and guiding them to graduate programs. This includes one student from a historically underrepresented group who will be supported by this project. Public outreach presentations will be developed to foster an interest in science and engineering among middle and high school students. The close collaboration between the universities, industry, and government lab will enhance technology transfer and expose the students to a more diverse educational experience.