Strengthening and toughening of a 2800-MPa grade maraging steel

A new high Ni, Ti and low Mo maraging steel based on 13Ni(400) maraging steel has been developed. The optimum heat treatment was found to be cryogenic treatment (CT) at 200 K followed by aging treatment at 773 K for 4 h in as-forged or solution condition. Optical and transmission electron microscopy (TEM) revealed that the precipitates, such as Ni3(Mo, Ti), were well developed in lath martensite. It achieved strength of 2700 MPa and fracture toughness of above 30 MPa m1/2. The balance among alloy elements and the removal of undissolved coarse particles ensured the good combination of strength and toughness by a normal thermomechanical treatment condition.