{"id":6618,"date":"2019-10-31T14:20:13","date_gmt":"2019-10-31T13:20:13","guid":{"rendered":"https:\/\/www.tag.it\/?p=6618"},"modified":"2021-03-09T14:45:41","modified_gmt":"2021-03-09T13:45:41","slug":"plasma-nitriding-popular-beliefs-unmasked","status":"publish","type":"post","link":"https:\/\/www.tag.it\/en\/plasma-nitriding-popular-beliefs-unmasked\/","title":{"rendered":"PLASMA NITRIDING: POPULAR BELIEFS UNMASKED"},"content":{"rendered":"\n

A study disproving some of the most deeply rooted beliefs about ion nitriding<\/h2>\n\n\n\n

Plasma is often defined as the \u201cfourth state<\/em>\u201d of matter<\/strong>, very similar to the aeriform one (such as a gas) but different from the latter because it consists of a set of electrons<\/a> and ions<\/a> (even if globally neutral, i.e. with a no total<\/a> electric charge<\/em>). A plasma is often formed by an electric discharge inside a gas, accompanied by the formation of light called glow discharge<\/em> (glow<\/em>) <\/strong>which, in the case of nitriding, is an ionized H2<\/sub>-N2<\/sub> mixture involving the use of a pulsed voltage source.The free electric charges thus formed allow the plasma to be a good conductor<\/a> of electricity<\/a> and to respond strongly to electromagnetic fields<\/a><\/strong>  (the plasma is affected by the magnetic field formed by the same current that flows through it): this feature allows the charged particles to be oriented and forced to follow precise trajectories.<\/strong> The knowledge of this phenomenon leads us to the possibility of directing our nitrogen ions (necessary for nitriding) onto any exposed surface<\/strong>, even those commonly considered impossible to treat with plasma nitriding technology.<\/p>\n\n\n\n\n\n\n\n

It is commonly believed that holes can only be nitrided to a depth not greater than twice its diameter<\/strong>, consequently details such as telescopes or extractor guide bushes do not undergo this treatment. This precaution is also used to avoid the risk of being subjected to hollow cathode <\/em>effects, a typical phenomenon of the plasma process involving overheating located inside holes and cavities, often followed by erosion and\/or local melting of the material in the affected area. <\/strong><\/p>\n\n\n\n

The same hollow cathode phenomenon could be triggered on figure areas of die-casting moulds for light alloys<\/strong>, characterised by the presence of different extraction holes and cavities in the figure area, with consequent considerable loss of mechanical and metallurgical characteristics of the core.<\/p>\n\n\n\n

These problems have been addressed at TAG with numerous tests and laboratory analysis until a satisfactory solution was achieved<\/strong>, which to date allows us to perform the nitriding treatment even in those cases normally considered impossible<\/em>.<\/p>\n\n\n\n\n\n\n\n

TEST PHASES<\/h3>\n\n\n\n

To summarise the tests performed, it is possible to say that we have defined three representative classes, identified as PLASMA 1, PLASMA 2 and PLASMA 3:<\/strong> in each of these configurations only one of the parameters characterising the plasma has been changed to finally identify the ideal combination.<\/p>\n\n\n\n

The method suggested by the manufacturers (i.e. standard parameters, identified as PLASMA 1) immediately revealed the inadequacy of the treatment for products with holes<\/strong>, having generated the hollow cathode with consequent localised melting of the steel near the hole inlet, as shown in the images below:<\/p>\n\n\n\n