Nitriding is a surface treatment process. As a result of diffusion to the steel surface of nitrogen, a hard layer is formed on the surface of the material with high abrasion resistance. Each material has a nitriding ability. Nitriding increases corrosion resistance and fatigue strength in some steels. Some steels reduce corrosion resistance.
Nitriding Applications Detail
Nitriding, one of the low temperature surface hardening processes; It is based on the formation of a hard layer on the surface by sending nitrogen atoms as intermediate atoms to the surface of the steel part. Salt bath and gas atmosphere can be used as nitrogen-providing medium.
Nitriding is carried out at temperatures as low as 480-540°C. At these temperatures, carbon steels are ferritic. Nitriding is applied to steels containing nitride-forming elements such as Al, Cr, Mo, Ti and V. In the nitriding process, the atomic nitrogen on the steel surface diffuses into the interior and reacts to form very fine nitride precipitates, usually 5-15 μm in size.
Partially soluble nitrogen in iron forms a solid solution with ferrite in compositions up to 6% and Fe4N crystalline phase in 6% nitrogen composition. In the nitrogen content of more than 8%, the ε phase is formed as the equilibrium reaction product Fe3N. The nitrided surfaces are in a layered structure and the outermost surface consists of white phase called white layer.
Such a surface layer is very hard and brittle and is undesirable since it is abraded by flaking in use. This layer can be reduced or made less brittle by special nitriding methods. The next region is the diffusion region which is hardened by the formation of the Fe3N crystalline phase ε.
Advantages of Gas Nitriding
High hardness is achieved in the following types of steel: Low alloy steels (nitralloy, 4340, 4140,…) Hot work tool steels 0.4 C-5 Cr-Si-Mo (1.2343, 1.2344, 1.2606,…) Tool steels 0.5-1.5 C-Cr-Mo-W-V (1.2363, 1.2379, 1.3343,…)
Corrosion resistant (for alloy steels and tool steels). Corrosion resistance increases in the following order; γ-nitride, ε-nitride and ε-carbonitride
There is no change in the core properties of the material.
