20th International Forgemasters Meeting - IFM 2017

With the rapid development of economic, it is urgently need to develop coal-fired power generation technology of further increased value of steam parameters in China. National 700℃ USC coal-fired power generation technology innovation consortium has been founded to develop the 700℃ USC technology and key components of steam turbine in 2010. All the forgings used for 700℃ and higher steam parameter are manufactured by Ni-base alloy, which is easy to crack and get mixed and coarse grain structure in forging process compared to heat-resistant steels. It is very difficult to obtain large Ni-base alloy forgings with grain size of 4-6 class after several times of upsetting and elongating. Numerical simulation is used to provide structure prediction and optimize wrought parameters in the deforming process of large 617 alloy forgings. Furthermore, we investigate the influence mechanism of heat treatment process on high-temperature stress rupture of Ni-base alloy forgings, and get excellent high-temperature microstructural stability with serrated grain boundary, nano scale gamma-prime precipitated phase and grain size of ASTM level 2-4 by optimization of heat treatment parameters. The extrapolated value of creep rupture strength is above 185 MPa at the condition of 700℃, 100000 hours.