Study on the Microstructure Evolution and Tungsten Content Optimization of 9Cr-3W-3Co Steel

• Main Authors: Longteng Ma, Yanfeng Wang, Guobiao Di
• Format: Article
• Language: English
• Published: MDPI AG 2018-10-01
• Series: Materials
• Subjects: tungsten; creep rupture life; lath substructure recovery; precipitation coarsening
• Online Access: https://www.mdpi.com/1996-1944/11/11/2080

Creep rupture tests of 9Cr-3W-3Co steel were conducted in the range of 120 to 200 MPa at 650 °C. The influence of stress on microstructure evolution was investigated in detail. In the high stress regime, a large density of dislocation was generated and induced precipitation of fine and dispersive particles. However, at lower stresses, a transformation from martensite laths to large size subgrains and a coarsening of precipitates took place due to significant recovery and loss of pinning effect during long term exposure. Thermodynamic results revealed decreasing tungsten content effectively retarded the coarsening behavior of M₂₃C₆ and Laves phase, hence further improvement of creep rupture time was achieved experimentally.