Stainless steel material technology

The nitriding of stainless steel is to increase its hardness, improve its abrasion resistance and corrosion resistance. The ferritic, martensitic and austenitic stainless steels and heat-resistant steels that are usually subjected to nitriding treatment. High-speed steel should be nitrided at low temperature for a short time.

　　The key to nitriding of stainless steel is to remove the passivation film. Passivation film is the reason why stainless steel is rust-proof and cannot be nitrided. Therefore, the key to nitriding stainless steel is to remove the passivation film on the surface. There are chemical and mechanical methods to remove the passivation film.

　　(1) Sandblasting. Before nitriding, the workpiece is sandblasted with fine sand at a pressure of 0.15-0.25MPa, until the surface is dark gray, and the surface dust is cleared and immediately enter the furnace.

　　(2) Phosphating. Phosphating treatment on the workpiece before nitriding can destroy the oxide film on the metal surface and form a porous and loose phosphating layer, which is conducive to the infiltration of nitrogen atoms.

　　(3) Chloride bubble. The blasting or finishing work piece is bubbled or coated with chloride, which can effectively remove the oxide film. Commonly used chlorides are TiCl2 and TiCl3.

　　 Ferritic, martensitic and austenitic stainless steels and heat-resistant steels are usually nitrided.

　　The chemical method is to soak the workpiece in 50% (volume) hydrochloric acid (temperature 70 degrees), and then clean it with water.