IMPULSE ION NITRIDING
As of 2007 AMP Paradowscy S.J. introduced engine valves finished in the process of impulse ion nitriding. This process is the most modern metal nitriding process worldwide. It is used in processing of surfaces of particular elements of machines, plant and tools under severe loads using the glow discharge generated by a pulsating electric field. This process makes use of the phenomenon of impulse discharge in thinned gas for saturation of metal surfaces with nitrogen. Ion nitriding is a modern form of gas nitriding , in which causes no threat for the natural environment.
The process is performed at low temperatures (from 400˚C, which is one of several advantages of ion nitridnig) and at reduced pressure. The most important reason for which this process is performed is to obtain high hardness values of nitride surfaces. The range of temperatures form 400 to 600˚C allows controlling the hardening process. The highest hardness values are obtained through nitriding within the range of 400 to 500˚C. The nitriding process is performed in a vacuum tank at a predetermined pressure. The processed charge becomes the negative end of the discharge (cathode), while tank walls – positive end (anode). Under the applied direct current (400 to 700V) the cathode surface emits electrons, which acquire energy in the electric field necessary for ionization of gas particles. Through collisions the ionized atoms and particles are accelerated and hit the cathode surface. Ions that bombard the surface lead to knocking out of iron atoms, alloying elements, coal, nitrogen and electrons indispensable for keeping up the glow discharge. Iron atoms bind witch active nitrogen atoms and settle on the surface in the form of nitrides and saturate the surface coats with nitrogen in the diffusion process. Through ion nitriding a layer of nitrides is produced witch non-porous monophase surface coat that assures homogeneity of physical and chemical properties. It is possible to control precisely the coat structure, which allows effective processing of larger elements with high dimensions related requirements and guarantees obtaining significant operational durability.
There is a growing variety of materials that may be hardened by this method, which allows obtaining durability increase. Ion nitriding very effectively enhances resistance to attrition and galling of nitrided coats. Application of the ion nitriding technology in engine valves improves their durability within the system of valve spindle-valve guide and reducing adhesion of carbon deposit in the head area. Through the application of this modern technology a corrosion resistant coat is achieved and general durability of valves is enhanced.
Application of the plasma ion nitriding technology produces valves with high mechanical properties – hardness, resistance to galling, attrition and wearing while neutral impact on the environment.