Solid solution nitriding of 15Cr-7.5Mn-2.6Mo duplex stainless steel was investigated by means of orthogonal tests. The results
show that the best technology would be using pure N 2 with P N 2=0.15MPa under the conditions of 1050℃×2h+1150℃×3h+1050℃×2h+1150℃×4h. The high nitrogen austenitic case with the depth of 1.62mm can be obtained. Orthogonal tests show that the type of nitriging medium has the most notable effect on
solid solution nitriding and the pressure in the furnace and the technology also has a notable effect. X-ray diffraction analysis 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 ferrite. In the other samples experienced solid solution nitriding and solution treatment the phase in the cases is only high nitrogen austenite. The results show that solid solution nitriding is a process that nitrogen purely diffuses in the austenite. The
diffusing activation energy in the conditions of P N 2=0.15MPa and 1050℃～1200℃ is 186.6kJ/mol.