A different approach was taken with the advent of the pulsed plasma nitriding (PPN) procedure, however, which was to pre-harden and temper, grind the tool/cutter undersize (slightly), plasma nitride and titanium coat.
The result was that the substrate material was now at 64 HRC with a diffused nitride case of 0.001-0.002 inches (maximum), which gave an approximate surface hardness of 1,000 HV minimum. This was followed by the titanium nitride in the same furnace that was used for the nitride procedure and the titanium deposition. The beauty of this process technique was that the titanium nitride case now had a “double support” of its core, with a nitrided case and then the deposition of titanium nitride.
The cutter was “grown” into the required size. The final process of the titanium nitride was accomplished by using a titanium-rich process liquid, which was evaporated. The residual titanium was ionized with the cutter at cathode potential for the deposition of the titanium.
The thickness of the resulting titanium nitride coat is determined by the process temperature, voltage, amperage and process pressure. The result was a very wear-resistant surface that was supported by a nitrided case with a prehardened and tempered core, thus reducing wear on the cutter.