INFLUENCE OF NICKEL AND MOLYBDENUM ON THE PHASE-STABILITY AND MECHANICAL-PROPERTIES OF MARAGING STEELS

The effect of nickel and molybdenum concentrations on the phase transf ormation and mechanical properties of conventional 18Ni(350) maraging steel has been investigated. Both of these elements act as strong aust enite stabilizers. When the concentration of molybdenum or nickel is g reater than 7.5 or 24 wt%, respectively, the austenite phase remains s table up to room temperature. In both molybdenum- and nickel-alloyed s teels, the austenite phase could be transformed to martensite by eithe r dipping the material in liquid nitrogen or subjecting it to cold wor king. When 7.5 wt% Mo and 24 wt% Ni were added in combination, however , the austenite phase obtained at room temperature did not transform t o martensite when liquid-nitrogen quenched or even,when cold rolled to greater than 95% reduction. The aging response of these materials has also been investigated using optical, scanning electron, and scanning transmission electron microscopy.