Residual austenite effect on the properties of cast stainless steels

A study was made of the possibility to decrease the inclination of the stainless maraging Cr-Ni-Co-Mo-steel to brittle fracture by obtaining austenite structure in the steel while maintaining its high strength (the yield strength sigma sub(y) (>=) 170 kgs/mm2). The residual austenite maintained in a direc g → M-transformation decreases the inclination of maraging Cr-Ni-Co-Mo-cast stainless steels to brittle fracture; the austenite obtained in a reverse transformation produces no such an effect. In the 00Kh12N5Kl3M6 steel the increase in the amount of the residual austenite from 5 to 30% leads to a better fracture toughness (it grows from 0.5 to 3.5 kgcm/cm2), to a worse sensitivity to crack formation (α+20 grows from 0.5 to 1.5 kgcm/cm2; Ksub(ls) grows from 170 to 300 kgs/mmsup(3/2)), and to a better sensitivity of notched samples to misalignment. Then the strength characteristics, especially the resistance to low plastic deformations, decrease (sigmasub(0.2) decreases from 170 to 130 kgs/mm2). For the steels investigated certain limits of the austenite content exist which secure the optimal strength and toughness. For the maraging Cr-Ni-Co-Mo-steel containing 18 to 28% austenite it is possible to obtain a high toughness (>=) 3.0 kgcm/cm2; αsub(p) (>=) 1.5 kgcm/cm2) with sigmasub(y) (>=) 170 kgs/mm2 and sigma sub(0.2) (>=) 130 kgs/mm2