microstructure difference P9 vs P91
microstructure difference P9 vs P91
(OP)
What differences in microstructure can be expected between P9 (9Cr-1Mo) and P91 (9Cr-1Mo-V). I am familiar with the P91 as we use it in the power industry however I have heard very little on the P9 material as we do not use it.





RE: microstructure difference P9 vs P91
RE: microstructure difference P9 vs P91
RE: microstructure difference P9 vs P91
P9 is also used in hydrogen and sulfur service in the petrochem industry at temperatures near 750 F, in which service the material will often times be specified in the normalized and tempered condition.
In terms of hydrogen cracking prevention, the required preheat is essentially the same as that for P91. PWHT is normally performed at 1350 F to 1400 F, which is only slightly lower than that normally prescribed for P91. The weld metal and substantial part of the HAZ will transform to martensite regardless of the initial heat treat condition of P9.
RE: microstructure difference P9 vs P91