The method for reproducing fine grained HAZ of W strengthened high Cr steel

The methods for reproducing fine grained heat affected zone of high Cr steel for creep test were investigated. This research was motivated by the need for reproducing uniform FGHAZ to investigate the creep damage process and untangle the coupling between thermal aging and cavitation (nucleation, growth, and coalesce), and the influence of states of stress. The two methods for producing FGHAZ were weld simulator and heat treatment in furnace. The microstructures, hardness, and creep rupture time under 923 K/100 MPa were investigated and compared with the actual FGHAZ of a weld joint. The FGHAZ specimens, re-produced by heat treatment in furnace, were also crept and compared with that of the base metal at 923 K/110 MPa and 100 MPa. It was found that (1) both the re-produced FGHAZ showed the similar microstructures and hardness as that of actual FGHAZ of a welded joint, (2) both the re-produced FGHAZ demonstrated the similar creep rupture time and it was shorter than that of a weld joint, and (3) in comparison with the base metal, the creep test of FGHAZ, reproduced by heat treatment in furnace, shows a short transitional period and early occurrence of a tertiary stage. It is concluded that (1) the uniform FGHAZ reproduced via a weld simulator is in the order of 10-15 mm long and is not big enough for creep test and (2) heat treatment in furnace can reproduce the representative FGHAZ required for creep research.