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The key to the nitriding of stainless steel is to remove its passivation film. The passivation film is the reason why stainless steel is rustproof and cannot be nitrided. Therefore, to nitride the stainless steel, the key is to remove the passivation film on the surface. The purpose of stainless steel nitriding is to increase its hardness and increase its resistance to abrasion and erosion. There are chemical and mechanical methods to remove the passivation film.Brass CNC Milling Part Supplier
(1) Sandblasting. Before the nitriding, the workpiece was sandblasted with fine sand under the pressure of 0.15-0.25 MPa, until the surface was dark gray, and immediately after entering the furnace, the dust was clearly visible on the surface.
(2) Phosphating. Phosphating the workpiece prior to nitriding can destroy the oxide film on the metal surface to form a porous phosphating layer, which is conducive to nitrogen infiltration.
(3) Chloride bubbles. The sandblasted or finished workpieces are soaked or coated with chlorides that effectively remove the oxide film. Commonly used chlorides are TiCl2 and TiCl3.
Ferritic, martensitic and austenitic stainless steels and heat-resistant steels are commonly used for nitriding.
The chemical method is to soak the work piece in 50% (volume) hydrochloric acid (temperature 70 degrees), then clean it with water;
Nitriding of high speed steel
Generally, high-speed steel nitriding is not suitable for 3 phases, otherwise the seepage layer will become brittle. According to the above rules, high-speed steel should be subjected to low-temperature nitriding at short time. Because at a lower temperature, the thickness of the penetrating layer is relatively slow, easy to control, and the nitrogen concentration on the surface of the penetrating layer is low. Short-term low-temperature nitride concentration is lower, better toughness. High-speed steel (w18cr4v) generally uses 510-520 degrees Celsius) diameter "15mm with 15-20min, the larger using 25-32min, large-scale use of 60min.Stainless Steel Milling Part Supplier