The addition of carbon to the atmosphere reduces the overall time of the nitriding process to generate a specific case depth. During plasma nitriding, three competing processes can simultaneously affect this oxide film; sputtering of the oxide, deposition of oxygen atoms/ions, and solution of some oxygen followed by diffusion of oxygen into the metal. Overlapping of the discharge zones may create non-uniform heating. Figure 11.2 (see also Plate VI between pages 392 and 393) shows this phenomenon observed in a tube. At a medium temperature of 480–600°C (conventional plasma nitriding), after etching with nital reagent, chromium nitride precipitation is observed throughout the entire nitrided case (Figure 16.11(a)). The glow discharge is influenced by pressure (Ruset, 1991) and the radiant heat losses, which are controlled by proper shielding (Ruset, 1994). The fundamental approach revealed an inefficiency of the process. They are also used on medium and high-carbon steels, titanium, aluminium and molybdenum. Plasma nitriding, also referred to as ion-nitriding, ... (steel or cast iron), its prior microstructure and the desired gear performance characteristics. The following improvements in properties can be achieved with nitriding and nitrocarburising: Nitriding and nitrocarburising are functional treatments for various components in many industrial sectors: The result of the plasma nitriding or plasma nitrocarburising process is increased surface hardness and wear resistance, lower wear coefficient, increased fatigue resistant, ductility, increased corrosion resistant, resulting with many times increased tool life of the machine parts or tools. The variation in the process efficiency is not only related to the pulse duration. Nitriding is the largest plasma nitriding center in Bulgaria. While increasing bias voltage clearly leads to faster compound layer growth, the total case is not affected. Surface microhardness increased significantly after shallow plasma nitriding. Accurate analysis of the diffraction patterns of the nitrided surface in Fig. It consists of a plasma nitriding at low temperatures and short times, to increase the hardness of the surface employing a shallow depth nitride formation in the surface of the iron.
Since the former may have complex three-dimensional shapes, it is important to conformally surround them with a “glow seam.” These workpieces are maintained below 600°C and subjected to N2/H2 mixtures at pressures between∼0.5 and 5 torr. Pulse durations within the range of microseconds are again different in their performance. Figure 11.2. Nitriding of thinner films does not seem to be very beneficial since the films were mostly removed by the sputtering action of the process.
Plasma nitriding/nitrocarburising is a modern thermochemical treatment which is carried out in a mixture of nitrogen, hydrogen and an optional carbon spending gas. This in turn reduces the stresses in the coating when loaded, leading to improved tribological properties and coating durability. The process provides abrasive wear resistance as a result of the high surface hardness achieved and also adhesive wear resistance which results from the characteristics of the compound layer and its ability to maintain a lubricant film.