Solid Solution Nitriding Technology of 15Cr-7.5Mn-2.6Mo Duplex Stainless Steel

摘要

Solid solution nitriding technologies of 15Cr-7.5Mn-2.6Mo duplex stainless steel were investigated by using of orthogonal tests. The results show that the best technology would be the processes of 1050 deg C X 2h + 1150 deg C X 3h + 1050 deg C X 2h + 1150 deg C X 4h under pure N_2 with P_(N2)=0.15MPa. The high nitrogen austenitic case with the depth of 1.62mm can be obtained. Orthogonal tests show that the type of atmosphere has the most notable effect on solid solution nitriding process; the pressure in the furnace and the nitriding processes has a notable effect. X-ray diffraction analyses results indicate that the main phases in the cases of the solution-nitrided samples cooled in the furnace are high nitrogen austenite, CrN, Fe_3O_4 and nitrogen containing ferrite. In the other samples experienced solid solution nitriding and solution treatment the obtained phase in the cases is high nitrogen austenite only. The results show that solid solution nitriding is a process that nitrogen absolutely diffuses in the austenite. The diffusing activation energy in the conditions of P_(N2) = 0.15MPa and 1050 deg C - 1200 deg C is 186.6KJ/mol.