Suppression against Distortion of Fe-15Ni-3Mn Age-hardening Steel due to Aging and Nitriding

This research project has been carried out in order to develop a new material whose dimensional aspects may be little affected during aging while providing excellent wear resistance, high strength, and good machinability. A series of Fe-Ni-Mn age-hardening steels were alloyed with different quantities of vanadium, cobalt, and molybdenum to improve their properties. Dimentional changes and mechanical properties were checked at various conditions of aging and nitriding.The results are summarized below.1. When 3 to 10 percent of vanadium is added to these steels, it is possible to reduce dimensional changes almost completely during aging.2. By adding 10 percent vanadium to these steels, it is possible to limit the expansion of the surface layer within 1 μm during nitriding and the nitrided layer hardness of HV 1 200 can be reached.3. High strength of 211 kgf/mm2 may be obtained through Fe-10V-3Mn steel with 2 to 3 percent of molybdenum.4. The best chemical composition in these steels is Fe-10V-15Ni-3Mn-3Mo. In this steel, tensile strength of 211 kgf/mm2, matrix-hardness of HV610 and nitrided layer hardness of HV 1 200 are attained by aging for 8 h at 450°C and nitriding for 3 h at 450°C.A total change in length due to nitriding is usually found to be no more than 1 μm.