2%Ni-1%Mo Composite-type Alloyed Steel Powder for Ultra High Strength and High Toughness Sintered materials

The composition of Ni and Mo containing composite-type alloyed steel powders was optimized for the production of ultra high strength, high toughness sintered components via compaction, sintering and heat treatment. A powder with 2%Ni and 1%Mo attained a high tensile strength of 1500MPa and a high unnotched Charpy impact value of 21J, when single-pressed, single-sintered and case hardened. Double-pressed, double-sintered and heat treated compacts made from the same powder showed an extremely high tensile strength of 1920MPa and a high unnotched Charpy impact value of 53J. The sintered compacts before heat treatment remained relatively soft and allowed machining and sizing. The strengthening was attributed to the strain-induced martensitic transformation of Ni-rich austenite.