Research Projects

Single layer grinding wheels are essentially superabrasives (diamond or cBN) wheels, exclusively used for high material removal rate (MRR) operations with high precision and for profile grinding. These tools have grits on its periphery bonded on a metal core by electroplating or brazed technology. These bonding technologies ensure larger protrusion of grits than that of conventionally bonded wheels, resulting in higher inter grit chip accommodation space. This feature makes the tools capable of high MRR grinding. However, both electroplated and brazed tools have their inherent shortcomings. The plated tools which solely relies on mechanical bonding mechanisms often found to be susceptible to grit pull out under large specific grit force at heavy duty cutting conditions. The brazed tools, on the other hand, though offers superior joint strength and larger grit protrusion due to its chemical nature of bonding through active brazing, are prone to bond level breakage instead of pull out. High brazing temperature and mismatched thermal expansion between components (diamond and substrate) challenge the tool life by introducing tensile residual stresses, forming brittle interfacial phases, and causing micro-cracks thereof leading to early grit failure. Although these tools are superior to electroplated tools, alleviation of residual stress is the immediate concern to enhance the performance of such tools. Researchers are thriving for technological solution which can potentially enhance the bonding strength so that the scope of applications can reach a new high and their application regime can be redefined with substantial superiority. In this regard, PI of the proposal, finds ion peening process to be a promising and potentially competent route to address the above challenges and interestingly effective for both electroplated and brazed bonding. With longstanding experience, the PI of the proposal has reached to an understanding that high energy accelerating metal-ion species from the plasma of PVD sputtering process, if allowed to bombard on electroplated and brazed route of diamond-steel joints, can conveniently accesses the complex micro-geometries and induce adequate compressive stress resulting in desired strengthening of these bonding systems. The electroplated one benefits from mechanical compaction and the brazed one by relieving its process induced tensile residual stress. It is reasonable to comprehend that the heavier metal ions (Ti, Cr and W planned for the current work) can serve the purpose better than gas ions (Ar, Kr). Moreover, the use of state-of-the-art HiPIMS (High power impulse magnetron sputtering) technology instead of DCMS (Direct Current Magnetron Sputtering) and necessary bias offset to substrate (relative to target) can help in enriching the plasma with higher metal ion population so that it can be potentially effective for the said purpose. In this proposed work, it is aimed to develop a novel ion peening technology with its full scope to enhance the diamond bonding strength and overall performance enhancement of grinding wheels. Detailed recipes of metal ion dominated ion peening with optimal regime of operating parameters developed to post-treat as-plated and as-brazed tools effectively. A comprehensive understanding on the process mechanics of bonding strength enhancement will be made available to the research and industrial fraternity, which will be earned through extensive experimental studies on simple single grit-specimens and industrial grinding wheel protypes using supporting characterisation (detailed in full proposal) tools. The proposed methodology expects enhancement of about 25% of bonding strength with very little addition of cost to originally manufactured products. The proposal finally offers to deliver patentable industry-ready recipes of ion peening and develop at least two variants of diamond grinding wheels (TRL 6) as industrial protypes, ready for field trials.