A more modern development of the nitriding process, also known as ion nitriding. In this process the component is made cathodic in relation to the furnace shell and nitrogen or ammonia gas is fed into the evacuated chamber. The glow discharge at the surface of the steel part produces atomic nitrogen by ionisation of the nitrogen or ammonia gas.
Although this process uses more expensive equipment, it has the advantage of being extremely controllable. Also it has a time advantage compared with conventional gas nitriding and lower nitriding temperatures can be used (450/590 C). Nitriding commences as soon as the surface ionisation occurs, and since it is not necessary to wait until the whole cross section of the component reaches nitriding temperature, cycle times are shorter. Also the improved reaction conditions existing in vacuo provide cleaner treated components. A major benefit is the lack of white layer, due to the surface reactivity of the glow discharge. This same characteristic makes the process better suited to the nitriding of stainless steels and other high alloy steels, as their surface passive layers are broken down by the glow discharge, allowing uniform nitriding to be produced.
