The Study On The Solid Solution Nitriding Of Stainless Steel

Solid Solution Nitriding of 304 Austenitic stainless steel and 3Cr13 Martensite stainless steel was investigated under the following technical parameters: temperature 900℃~1150℃,nitrogen pressure 0.1Mpa~2MPa, nitriding time 2h~16h, three cooling ways: furnace cooling, air cooling, water cooling. The microstructure, phase, the distribution of nitrogen concentration, microhardness of the nitrided layer of 304 Austenitic stainless steel and 3Cr13 Martensite stainless steel was measured by SEM, EPMA, X-Ray, microhardness instrument in different Solid Solution Nitriding parameters.The analysis of microstructure showed that: austenitic was obtained in the nitrided layer of 304 Austenitic stainless steel after nitriding and cooling in air or water in the above parameters. The microstructure of the nitrided layer is basically same to the inner microstructure, precipitation of nitride appears at the grain boundaries in furnace cooling; lots of white compounds precipate at the pearlite grain boundaries after nitriding and cooling in furnace of 3Cr13 Martensite stainless steel, martensite was obtained in water cooling, compounds in the nitrided layer increase with the nitrogen content on the surface, when the nitrogen pressure is 0.1MPa, no compounds was observed in the nitrided layer, when the nitrogen gas pressure is 2.0MPa, lots of white compounds was observed in the nitrided layer.The analysis results of the distribution of nitrogen concentration showed: the surface nitrogen content and nitrided layer depth of nitrided sample increase with the nitriding temperature; nitrided layer depth is in direct proportion to the root of nitriding time; the nitrogen content on the nitrided sample surface is in direct proportion to the root of nitrogen pressure.The X-ray analysis results showed: Y -Fe was obtained on the surface of 304 Austenitic stainless steel after nitriding and cooling in water; when the nitrogen content is 0.3%, was obtained on the surface of 3Crl3 Martensite Stainless steel after nitriding and cooling in water, when the nitrogen content on the surface is 0.6%, a and Y were observed.The microhardness analysis results showed: nitrogen solubilizes in the state of solid solution can obviously improve the microhardness, the microhardness of the nitrided layer increases with the nitrogen concentration. When the content of nitrogen in the state of solid solution of 304 Austenitic stainless steel is nearly to 0.5wt%, the microhardness will be improved to almost 280HV0.1 from 200HV0.1; When the content of nitrogen in the state of solid solution of 3Crl3 Martensite stainless steel is nearly to 0.5wt%, the microhardness will be improved to almost 700HV0.1 from420HV0.1.