A series of experiments were carried out to study the influence of low temperature plasma nitriding on the mechanical properties of AISI 420 martensitic stainless steel. Plasma nitriding experiments were carried out for 15 h at 350℃by means of DC- pulsed plasma in 25%N_2+75%H_2 atmosphere.The microstructure,phase composi- tion,and residual stresses profiles of the nitrided layers were determined by optical microscopy and X-ray diffraction.The microhardness profiles of the nitridied sur- faces were also studied.The fatigue life,sliding wear,and erosion wear loss of the untreated specimens and plasma nitriding specimens were determined on the basis of a rotating bending fatigue tester,a ball-on-disc wear tester,and a solid particle ero- sion tester.The results show that the 350°nitrided surface is dominated byε-Fe_3N andαN,which is supersaturated nitrogen solid solution.They have high hardness and chemical stabilities.So the low temperature plasma nitriding not only increases the surface hardness values but also improves the wear and erosion resistance.In addition,the fatigue limit of AISI 420 steel can also be improved by plasma nitrid- ing at 350℃because plasma nitriding produces residual compressive stress inside the modified layer. A series of experiments were carried out to study the influence of low temperature plasma nitriding on the mechanical properties of AISI 420 martensitic stainless steel. Plasma nitriding experiments were carried out for 15 h at 350 ° C by means of DC- pulsed plasma in 25% N2 + 75% H_2 atmosphere.The microstructure, phase composi- tion, and residual stress profiles of the nitrided layers were determined by optical microscopy and X-ray diffraction. The microhardness profiles of the nitridied sur- faces were also studied.The fatigue life, sliding wear, and erosion wear loss of the untreated specimens and plasma nitriding specimens were determined on the basis of a rotating bending fatigue tester, a ball-on-disc wear tester, and a solid particle ero-sion tester. results show that the 350 ° nitrided surface is dominated byε-Fe_3N andαN, which is supersaturated nitrogen solid solution.They have high hardness and chemical stabilities.So the low temperature plasma nitriding not only increases the su In addition, the fatigue limit of AISI 420 steel can also be improved by plasma nitridation at 350 ° C because plasma nitriding produces residual compressive stress inside the modified layer.