Development and quality assessment of multi-point brazed diamond dressers produced by active brazing under high vacuum
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In the current work, multipoint single layer brazed diamond dressers were indigenously developed by high vacuum brazing technology using Ni-Cr and Ag-Cu-2Ti alloy. The vacuum level was maintained in the range of 10−6–10−7 mbar. To assess the quality, the developed dressers were subjected to eight dressing cycles with increasing grit penetration depth. The Ag-Cu-2Ti alloy, possessing a lower liquidus temperature of 820 °C, showed a superior grit retention ability compared to Ni-Cr alloy, having a higher liquidus temperature of 1050 °C. Higher thermal residual stresses developed in the case of Ni-Cr alloy, due to higher brazing temperature and difference in Young’s moduli and the coefficient of thermal expansion of the diamond grit, filler alloy, unfavorably led to the premature bond level failure of brazed diamond grit under lower specific loads. Elevated brazing temperature and formation of unfavorable intermetallic phases were found impairing the effectiveness of Ni-Cr alloy and caused severe graphitization of diamond. On the other hand, the silver-based bond experienced a potential threat of rapid wear by the hard bond-abrasive system of the grinding wheel during dressing. Localized “scooping” of bond material was observed in Ag-based bond layer securing diamond grits. Through a separate pin-on-disc test, it was demonstrated that this alloy received a substantial wear rate of 3.364 mm3/min and exhibited deterioration of frictional behavior, despite the presence of silver. The Ag-Cu-2Ti alloy with lower brazing temperature and lower tendency of graphitization has otherwise a more promising scope but only if the composition is suitably altered to bring in significantly higher abrasion resistance in its mechanical characteristics.
KeywordsMulti point diamond dresser Active brazing Bond strength Interfacial metallurgy Microstructure Abrasive resistance
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The authors would like to acknowledge the following organizations for their support: Department of Higher Education, Ministry of Human Resource Development, Government of India; Department of Science and Technology, Project No. MEE/13-14/315/DSTX/AMIA, Government of India; DST-FIST II, Project No. SR/FST/ET11-059/2013 (G), dated: 25-09-2014, Government of India and ElementsixTM, Em Pee Syndichem Pvt. Ltd., Mumbai, India.
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