Nanocomposite TiAlSiN coatings were deposited on WC-Co blocks and 2-fluted end-mills using High Power Impulse Magnetron Sputtering (HiPIMS) technology, with variations in pulse frequency. The immediate impact on the V-I signature and subsequent results on coating characteristics were thoroughly investigated. Both the substrate and target were negatively biased in pulsed mode, but the voltage pulses on the substrate were set with an offset of 40 µs relative to those on the targets to prevent gas ion entrapment within the coating. The analysis delved into the variation of elemental composition, cross-sectional morphology, surface topography, hardness, and adhesion strength of the coatings deposited under different pulsed frequencies. TiAlSiN at the highest frequency exhibited significant improvements in hardness and scratch resistance. Higher deposition rates were achieved with a higher frequency but at the expense of surface smoothness.
To evaluate the performance of the nanocomposite TiAlSiN, the coated end-mills (approximately 3 µm coating thickness) underwent high-speed milling of austenitic stainless steel, known to cause severe diffusive wear on uncoated carbide tools. The effectiveness of TiAlSiN coating was investigated under dry, wet (flood, 25 l/hr.), and near-dry (MQL, 250 ml./hr.) conditions. TiAlSiN coated tools experienced severe diffusive adhesion of work material on their cutting edge during dry machining. The near-dry approach, with a cutting fluid consumption rate of only 250 ml./hr., proved to be more effective and environmentally friendly. No delamination of the coating was observed under dry, flood, and near-dry environments. In a near-dry environment, a maximum of 20% reduction in cutting force and a 45% reduction in roughness (Ra) were recorded compared to a flood environment. The performance of the HiPIMS deposited TiAlSiN coated tools was also compared with that of commercial TiAlN and commercial TiAlSiN tools and found to be potentially more effective in milling SS304 steel.