Effect of aging treatment on microstructure and properties of additively manufactured maraging steel

Abstract

Additively manufactured grade 300 maraging steel (AM300) exhibits high strength but low elongation, because the precipitation strengthening effected by aging treatment has not been fully took effect. This work aims to optimize the aging treatment process of AM300. It was aged at 420°C, 500°C and 550°C for 4 h, respectively. It was found that the aged AM300 exhibited the best combination of strength and ductility (ultimate tensile strength (UTS) was 1740 MPa, total elongation (TE) was 10.2%, hardness was 520.4 HV) at 420°C. As compared to the non-aged AM300 (UTS = 1060 MPa, TE = 4.2%, hardness = 349.2 HV), the UTS, TE and hardness were increased by 64.1%, 142% and 49%, respectively.

Laser additive manufacturing of steels

“…The tensile properties of as-built maraging steels are comparable to their wrought counterparts [303,312,399]. The ultimate tensile strength of most as-built maraging steels are over 1 GPa [180,301,302,[306][307][308][309]312,313,[316][317][318]321,325,327,333,336,337,400,401].…”

“…Similar to austenitic and PH stainless steels processed by LAM, cellular/dendritic structure is common in 18Ni-300 maraging steels as shown in Figure 32(a,b) [321], indicating microsegregation and high-density dislocations along the inter-cellular/dendritic area. As shown in Figure 32(e), the inter-cellular/dendritic areas are enriched with Ti, Mo, and Ni, which is related to the phase distribution in LAM processed maraging steels.…”

“…The tensile properties of as-built maraging steels are comparable to their wrought counterparts [303,312,399]. The ultimate tensile strength of most as-built maraging steels are over 1 GPa [180,301,302,306–309,312,313,316–318,321,325,327,333,336,337,400,401]. The high strength should be primarily originated from the fine martensite laths (see Figures 32 and 33).…”

“…The low volume fraction of precipitates in the as-built samples corresponded to the low strength. Thus, aging treatment is usually performed after LAM processing to further strengthen PH steels [145,273] and maraging steels [297,302,313,318,321,327]. Yadollahi et al [145] reported that the ultimate strength and fracture strain of 17-4 PH samples in the longitudinal test direction were up to ∼1400 MPa and 10% after aging treatment at 482°C for 1 h after solid solution treatment at approximately 1040°C for 30 min, which is comparable to the peak-aged wrought alloys (see Table 7).…”