Fabrication Of High Nitrogen Stainless Steel By High Temperature Nitriding And Investigation On Microstructure And Performance

High Nitrogen stainless steel shows high strength and good corrosion resistance due to its high Nitrogen content. As a kind of new engineering material, high Nitrogen stainless steel plays more and more important role in industrial production. The factors affect the high temperature Nitriding process for stainless steel Cr17-14Mn-2Mo-0.4N, including the heating temperature, heating time and Nitrogen pressure, were investigated by optimizing technique parameter in the artical. The factors affecting the microstructure, mechanical performance and resisted corrosion of high Nitrogen stainless steel were discussed in the same time. The results are as follows:When the heating temperature is not lower than 1200℃, the heating time is not less than 24h, the Nitrogen pressure from 0.2MPa to0.5MPa, the stainless steel will obtain the single side Nitrogen layer thickness approximately above 2.0mm. The average nitrogen content reaches above 1.1%, which increased 2 times comparecd with the original material. The completely austenitic Nitrogen layer of stainless steel can be obtained by the high temperature Nitriding. The tensile strength of the Nitriding specimen is higher than unnitriding specimen, the elongation and the reduction of area is not obviously reduces, still maintained in a high level. The corrosion resistance of Nitriding specimen is better than unitriding specimen in 37℃ , 0.9 %NaCl solution and 37℃artificial plasma, especially the pitting corrosion resistance . Its corrosion resistance is improved with increase of Nitrogen content, and the Nitrogen content is increased per 0.01%, the pitting corrosion potential can be improved above 10mV. The pitting corrosion potential of high Nitrogen stainless steel specimen produced by the high temperature Nitriding condition of 1200℃/0.3MPa/24h in 37℃, 0.9%NaCl solution is approximately 1200mV, more higher than the pitting corrosion potential of unnitriding specimen (320mV).The Nitrogen content distribution model of high temperature Nitriding can be inferred from atomic diffuse theory and Nitrogen layer hardness test result . The model has the ability toforecast the Nitrogen content of Nitrogen layer in nickel-free duplex stainless steel to some extent, and to evaluate the Nitrogen content of different technique , plays the instruction role to the high temperature Nitriding technique.