For welding the specified base metals—P9 to P9, P5B to P5B, and P5B to P8 (304H)—the selection of consumables (filler metals) must
consider the chemical composition, mechanical properties, and service conditions of these materials.
Consumables for Joining P9 to P9
· P9 corresponds to 9Cr-1Mo steels (Chromium-Molybdenum steels).
· Recommended filler metals for welding P9 to P9 are typically E80S-B8 or E8016B8/E8018-B8 electrodes for GTAW or corresponding
solid wires for SMAW.
· Preheat and post-weld heat treatment (PWHT) are essential to avoid cracking and ensure weld integrity.
Consumables for Joining P5B to P5B
· P5B includes 5%Cr, 0.5%Mo often used in high-temperature, creep-resistant applications.
· Common filler metals include ER80S-B6 or E8016-B6/E8018-B6 low alloy wires, which match the Cr-Mo content and provide good
weldability and creep strength.
· Preheat and post-weld heat treatment (PWHT) is mandatory for P5B welds to achieve crack free weld.
Consumables for Joining P5B to P8 (304H SS)
· This is a dissimilar metal weld between a Cr-Mo steel (P5B) and an austenitic stainless steel (P8 304H).
· The filler metal must accommodate differences in thermal expansion and metallurgical compatibility.
· Nickel-based filler metals such as ERNiCrFe-2 or ERNiCrFe-3 (AWS A5.11 or A5.14 classifications) are preferred for joining these dissimilar
because they provide good corrosion resistance and reduce the risk of cracking caused by dilution and thermal mismatch.
· Austenitic stainless steel fillers like ER309 are not recommended for P5B to P8 welds due to dilution issues and stress concentration. Instead,
nickel-based alloys with higher corrosion resistance and ductility are used.
· This selection ensures metallurgical compatibility, mechanical integrity, and service life of the welds involving these materials. Proper welding
procedure and heat treatment are critical, especially for creep-resistant steels like P5B and P9.
C Sridhar.
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