Factors Influencing the Fracture Toughness of PH13-8Mo Under Peak Aging at 510 °C
摘要
In this work, to identify factors governing the fracture toughness of PH13-8Mo steel under peak aging at 510 °C, four samples were collected from different sections of bars prepared using a vacuum induction melting and vacuum consumable arc melting duplex process. The samples underwent solution treatment at 925 °C followed by aging at 510 °C. The results showed that all samples exhibited similar yield strength (~1400 MPa) and ductility (~19 pct) but markedly different fracture toughness (KIC: 62.7 to 122 MPa m1/2). It was confirmed that the Ni–Al precipitation behavior and high-angle grain boundaries were not the governing factors. Notably, δ-ferrite was identified as the primary detrimental phase, promoting crack propagation. Conversely, fine lath martensite and high geometrically necessary dislocation density were identified as critical factors for enhancing toughness. Although reversed austenite promoted toughening, its limited content restricted its effect compared to the embrittlement effect of δ-ferrite. These findings demonstrate that optimizing toughness at peak strength requires minimizing the δ-ferrite content and refining the martensitic substructure.