| 1RK91 mar-aging stainless steel was invented in the 1990s’by AB Sandvik Company. It has been widely used in various applications such as shaver blades, surgical instrument and so on for its high toughness, high intensity, outstanding resistance to over-aging, excellent corrosion resistance and good weldability. Our team has done a lot of experiment to explore the effect of different heat treatment, plasma nitriding and Ti content on the microstructure and properties of this alloy. However, The effect of Mo content on the microstructure and properties has not been studied yet. For this reason, the present research is dedicated to exploring the effect of different Mo content on the microstructure and property of 1RK91.Four alloys referred to as A, B, C, D with increasing Mo content (A-0.1%, B-1%, C-2%, D-3%) were melted with vacuum induction furnace. Different solution treatment, cold working and aging treatment were applied to the four alloys and their microstructures, hardness and corrosion resistance were investigated. The roles of Mo content played are discussed in this work.Results showed that solution temperature has no apparent effect on hardness when the temperature of solution treatment is at 950℃-1050℃. Mo strengthened the matrix by solution strengthening. Hardness increased when the Mo content increased. It is found that 5-phase precipitated in alloys with higher Mo content (3.3%for example) when solution treatment temperature was lower (950℃-1050℃). The amount of 5-phase decreased at higher solution temperature.It is also found that Mo has no apparent effect on hardness of 1RK91 after deformation or in the early stage of aging. The R’phase enriched with Mo and precipitated in the later stage of aging may be beneficial to the hardening. Mo can also retard the coarsening of Ni-enriched precipitates.A higher Mo content can not only ensure higher peak hardness but also retard softening of 1RK91 at higher aging temperature. Mo can effectively enhance the corrosion resistance of 1RK91 mar-aging stainless steel in Cl containing oxidating solution.2%Mo is essential to corrosion resistance of this alloy. Solution temperature seems to hardly affect the corrosion resistance of the alloys with high Mo content. However, to alloys with lower Mo content, solution temperature show certain effect on the corrosion resistance. When solution annealed at 950℃-1050℃, corrosion resistance of alloy A degraded. Short-time aging is harmless to the corrosion resistance of the alloys, while prolonged aging tend to decrease the corrosion resistance. After aging for 400h at 475℃, corrosion resistance degraded severely. |
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