We have carbon steel pressure vessel built to ASME VIII Div 1 subject to Furnace PWHT per Code, due to restriction of internal painting we use stainless steel pipe for nozzle neck welded to carbon steel welded and will undergo PWHT after welding, we have qualified ASME IX WPS/PQR P1 to P8 with PWHT specimen.

The Client is asking whether 'sensitizing' failure during operation will likely to occur and how this will affect the welding (CS to SS with PWHT), I have replied the question referring to Non mandatory appendix A - A350 ASME Sect II Part D.

However, I still need other reasons and suggestions to convince my Client

Thanks