Characterization of mechanical and corrosion behavior of low-nickel cobalt-free maraging steel alloys

Abstract

Three different samples of maraging steel alloys were characterized before and after aging process. Optical microscopy and SEM investigation have shown a clear precipitation as a result of the aging process. The EDX analysis supports the hypothesis of the formation of titanium and molybdenum rich precipitates at the grain boundaries after aging. The mechanical properties of the steel alloys were tested at room temperature as well as at elevated temperatures. High values of mechanical properties were obtained at room temperature. Nevertheless, the mechanical properties of the steel alloys dropped severely at elevated temperatures due to the austenite reversion phenomenon. This may also explain the high ductility in the material at elevated temperatures resulting in the high values of elongation which exceeded 50% in some samples and the significant drop in the values of the modulus of elasticity. The increase in the titanium mass percentage caused an increase in the value of hardness; however, it resulted in the embrittlement of the material and lowering the values of impact toughness. The corrosion behaviour of the alloys was tested in 3.5% NaCl. The solution treated samples have shown a more passive behavior than the aged samples did; however, the aging process has resulted in a significant enhancement of the corrosion resistances of the alloys.