Since 2007, Paradowscy AMP Sp. z o. o. has been introducing plasma nitrided engine valves to both the domestic and international markets through the impulse ion nitriding process. This process is the most advanced metal nitriding process in the world. It is used for surface treatment of heavily loaded machine parts, devices, and tools utilizing glow discharges generated by a pulsating electric field. In this process, the phenomenon of impulse discharge in rarefied gases is used to saturate the metal surfaces with nitrogen. Ion nitriding is a modern version of gas nitriding, in which ammonia is replaced by nitrogen and hydrogen, posing no threat to the natural environment.
The process is conducted at low temperatures (from 400°C, which is one of the many advantages of ion nitriding) and under reduced pressure. The primary reason for conducting this process is to achieve high hardness values of the nitrided layers. The temperature range from 400 to 600°C allows for control over the hardening process. The highest hardness values are obtained after nitriding in the range of 400÷500°C. The nitriding process is carried out in a vacuum chamber with pressures ranging from 1 to 10 hPa. The treated load serves as the negative pole of the discharge (cathode), while the walls of the chamber are the positive pole (anode). Under the influence of applied DC voltage (400÷700V), the surface of the cathode emits electrons, which in the electric field gain the energy necessary to ionize gas molecules. As a result of collisions, ionized atoms and molecules are accelerated and strike the cathode surface. The bombarding ions cause the ejection of iron atoms, alloying elements, carbon, nitrogen, and electrons necessary to sustain the glow discharge. Iron atoms combine with active nitrogen atoms and deposit on the surface as nitrides and saturate the subsurface layers with nitrogen in the diffusion process. Ion nitriding results in nitride layers with a non-porous monophase subsurface zone ensuring uniform physicochemical conditions. It is possible to precisely control the structure of the layer, allowing for effective treatment of large elements with high dimensional requirements and ensuring high operational durability.
Versatility, quick adaptation to customer needs, and above all consistently high product quality shape the image of PARADOWSCY AMP, which forms the basis for acquiring new markets.
The range of materials that can be hardened by this method is constantly expanding, achieving up to a fivefold increase in durability. Ion nitriding significantly increases the resistance to wear and seizure of the nitrided layers. The use of ion nitriding technology in engine valves increases their durability in the valve stem-guide system and reduces carbon adhesion in the valve head area. The application of this modern technology enhances the overall durability of the valves. Test results for valve steels in the initial state and after nitriding, measured by the linear method, show more than five times lower wear values for nitrided steel.
By using plasma ion nitriding technology, we can obtain valves with high mechanical properties – hardness, resistance to seizure, wear, and abrasion. This technology shows many advantages compared to previously used chrome plating and salt bath nitriding, surpassing them additionally in terms of environmental neutrality.
