Structure heredity, aging and stability of strengthening of Cr–Ni maraging steels

Aging processes, structure heredity and stability of strengthening of maraging steels (including nitrogen-containing ones) subjected to thermal and thermomechanical treatment, were investigated using X-ray structure analysis, light and electron microscopy and mechanical testing. The thermomechanical treatment is accompanied by inheritance of the substructure of the deformed austenite by martensite. That results in an enhancement of strain aging and thermal stability of the martensite strengthening. The nitrogen-alloying results in austenite aging, changes its composition, and correspondingly retards recrystallization but differently influences thermal and mechanical stability of the austenite, martensitic transformations and martensite aging. Kinetics of the aging as well as cooling- and strain-induced martensitic transformations were studied. Nitrogen-containing two-phase steels having σb = 1300–1500 MPa are recommended as economically alloyed maraging steels.