Study on the Post-Weld Heat Treatment Cracking of Ni-Base Heat Resistant Alloys (Part 1)
Features of Post-Weld Heat Treatment Cracking and Precipitation Behaviors of γ'Phase
1978 Volume 47 Issue 2 Pages 99-104
Details
1978 Volume 47 Issue 2 Pages 99-104
In this study, the criterion of post-weld heat treatment (PWHT) cracking was considered in accordance with the features of PWHT cracking and precipitation behaviors of γ' phase were also examined.
The results obtained in this study are as follows;
1) Typical PWHT crackings of Ni-base heat resistant alloys usually initiate at coarse grain boundaries adjacent to the weld interface where residual stress concentrates. Consequently, the deformability of material in stress concentrated region is presumed to be closely related to the PWHT cracking susceptibility.
2) γ' phase precipitates very rapidly in the temperature range from 800°C to 900°C. Each shortest incubation time of γ' phase precipitation in Heats 702A and 722A is about 8 sec at 900°C and 80 sec at 800°C respectively.
3) From the kinetics of aging, coarsening of γ' phase is obeyed with the theory of Ostwald ripening and controlled by the diffusion process of Al in matrix.
