(1) stainless steel surface is usually the ultimate secret by a very thin blunt membrane (Cr2O3, Fe2O3, NiO, etc.) is covered. This passive film is strong and stable, has a strong resistance to permeation effects. In the ion nitriding conditions, due to the continuous bombardment of the plasma at high speed potential of the workpiece and the resulting sputtering effect can be all-round, the whole process of destroying the native passive film of stainless steel surface and regeneration of passive film, activated metal subsurface world pie network information , which is conducive to the adsorption and diffusion of nitrogen.
(2) ion nitriding, while maintaining the high surface hardness can increase the depth of hardened layer, resulting in a more dense nitrided layer. Dense nitrided layer to obtain high wear resistance, and studies have shown that parts of ion nitriding gas nitriding of parts with high wear resistance, and the layer gradient gentle, no obvious boundaries with the matrix, usually 500 ~ 550 ℃, the ion speed is 2 times of the gas permeation speed.
(3) plasma nitrided at the lower temperatures and faster speeds, so the parts corrosion resistance than gas nitriding is better, better finish sided increase after the nitriding The amount of deformation is not greater than 0 World pipe network reported that the world's steel pipe network to provide the world's steel pipe network editor .02mm, than gas nitriding 1 times, can be used as precision parts last a machining process.
(4) plasma nitriding can be shaded to cover up the local part of local surface nitriding, the nitriding stainless steel surface and still maintain the original corrosion resistance.
(5) ion nitriding layer organizations can control, you can add reminders penetration enhancers to improve the nitriding effect. The tests showed that acetone, rare earth elements, titanium and a variety of activator infiltration, infiltration speed can be increased by about 20%.
2, nitriding of stainless steel material selection
2.1 nitriding stainless steel classification of nitriding of stainless steel including stainless steel, austenitic stainless steels, and precipitation hardened stainless steel in Class 3. Martensite series 1Cr13, 2Cr13, 3Cr13, 1Cr5Mo 1Cr13Al and 2Cr13Mo; austenitic series: 0Cr18Ni9, 1Cr18Ni9, 1Cr18Ni9Ti Cr18Ni12Mo2Ti and 4Cr14Ni14W2Mo; there 0Cr17Ni4Cu4Nb as the representative of the precipitation hardening stainless steel, have a good nitriding hardening effect. In addition, the ferrite Cr17, Cr17Ti and martensite austenite 15CrMoV such as nitriding effect.
2.2 nitriding of stainless steel material selection from the permeable good point of view, the choice of alloying elements in stainless steel with nitrogen affinity strong nitriding treatment. First, these elements enable the matrix structure in a relatively high temperature stability allows parts nitriding at higher temperatures, deformation of parts to reduce the nitriding time. Some data indicate that the steel containing 0.6% to 1% vanadium, not only to grain refinement, and inside the grains and grain boundary precipitation of dispersed nitrides nitriding elimination of chrome steel along the grain boundaries in the nitriding continuous nitride network, significantly improved wear resistance and fatigue strength of layer, suitable for precision parts to maintain precision. Stainless steel containing titanium nitriding a good influence, not only at high temperatures to maintain the stability of the organization, and is a reminder penetration of the nitriding. When the titanium and carbon steel (mass ratio) for 65 to 95, allows infiltration significantly improved hardness of the nitride layer, titanium steel nitriding temperature at 600 ℃, nitriding can be used for middle load high friction and alternating load work. Alloying elements in the the nitriding sub-surface layer formation of the dispersed hard nitride skeleton, such as Cr2N, hardness up to 1600HV; the formation of nitrogen carbon compounds containing Mo alloy steel, nitriding, hardness up to 1800HV; Ti nitriding material Ti2N was, the hardness of TiN 1200 ~ 2000HV; V nitriding material hardness up to 1900HV; more unique content of Al in steel nitriding effect. Practice has proved that the martensitic stainless steel is easier than the austenitic stainless steel nitriding treatment. Such as 2Cr13 stainless steel ion nitriding 8h formation of 0 .15 mm diffusion layer, and 700 ~ 800HV hardness; 1Cr18Ni9 by ion nitriding 10h only the formation of 0 .08 0 .12 mm layer, even if the extension for a long time, the after penetrating rate is very slow, can be seen in the case of corrosion resistance allows to improve the wear resistance, should give priority to good advantage martensitic stainless steel permeability. Usually austenitic stainless steels in the nitriding process, due to the diffusion coefficient of nitrogen in which much lower than αFe, the presence of a large number of alloying elements (such as 1Cr18Ni9Ti containing alloying elements about 30% the 2Cr13 of 2 times), they will hinder the nitrogen atom diffusion process, so you can get a higher surface hardness, and to a deeper layer thickness is more difficult.
2.3 infiltration in the use of nitrogen stainless steel martensitic stainless steel 1Cr13, 2Cr13, 3Cr13 below 30 ℃, weak corrosive medium (such as salt water, some of the low concentration of organic acid, nitric acid) are good corrosion resistance to seawater, fresh water, water vapor, air, and also have sufficient corrosion resistance; Cr17, Cr17Ti resistance to oxidizing acids, such as a certain temperature and concentration of nitric acid, and most of the organic acids (acetic acid , except for formic acid, lactic acid, oxalic acid) and organic salts in aqueous solution; Cr17MoTi higher acid resistance, such as organic acids (acetic acid, acid and its hot acid), its corrosion resistance is even better than 1Cr18Ni9. Austenitic stainless steel 1Cr18Ni9Ti, usually with strong corrosive medium especially Cr18Ni12Mo2Ti, better corrosion resistance, the use of low concentrations of sulfuric acid, boiling phosphoric acid, formic acid, acetic acid, urea, caustic soda industry and low molecular weight naphthenic acid, low molecular weight fatty acid production equipment for the food and drink, pharmaceutical industry, the product "Green". The above materials by ion-nitriding treatment, surface hardening effect can be achieved, multi-port ring for a centrifugal pump, shaft protective sleeve, impeller, bearing wear ring, piston, piston, connecting rod, and stirrer sleeve, centrifuges pusher plate, scraper, and high pressure valve seat and valve stem, etc., the service life doubled.
ion advantages of nitrogen stainless steel
Stainless steel is used for to strengthen to learn corrsive, has been widely used in civil processing industry, pharmaceutical, food and drink. However, due to the low hardness and poor wear resistance, it is restricted in many occasions. Particle suspension parts in relative friction conditions, the wear resistance has become a prominent contradictions. The past 20 years, the ion nitriding nitrogen technology development and improve the important method to create a stainless steel surface hardening, plasma nitriding has become a better choice of stainless steel, titanium and its alloys to strengthen methods.