Weldstan thanks for your response.
Service is steam with thermal cycling as this is cold reheat line.
Operating Pressure: 49bar
Operating temprature: 510C
PWHT shall be eliminated and temper bead welding shall be done.
You were out of your depth with the first question; with temper bead welding you confirmed you are now way out of your depth.
Consult a welding engineer familiar with the application.
"Everyone is entitled to their own opinions, but they are not entitled to their own facts."
If you have access to EPRI publications, search there. I have read many similar artiicles but am too long retired to search an I no longe have access to their publications. I believe that you will need a transition material pup between the two to get best service life.