2.1 | Material and specimens
Two groups of turbine blades are tested in the study. One group is
treated by the PSP treatment, and the other group of turbine blades that
are not treated by PSP is the same as those used in the actual outer
field. The blades are cast with the K403 nickel-base superalloy. The
heat treatment of these blades is carried out at 1210°C in a pit-type
gas carburizing furnace for 4h. Then, the blades are cooled to room
temperature in air.
The chemical composition of K403 is shown in Figure 1(a). The
microstructure is observed as the γ phase, γ′ phase and (γ + γ′)
eutectic phase and MC carbides
(Figure 1(b)). The γ solid
solution is the matrix phase, and the γ′ phase is the main strengthening
phase. The γ′ phase whose mass fraction is 57% has a surface-centered
cubic structure. The volume fraction of (γ + γ′) eutectic is 2%.