Welding in the World

, Volume 56, Issue 7–8, pp 10–17 | Cite as

Improvement in Creep Resistance of Modified 9Cr-1Mo Steel Weldment by Boron Addition

  • Chitta R. Das
  • Shaju K. Albert
  • Arun K. Bhaduri
  • Baldev Raj
  • Jaganathan Swaminathan
  • Budaraju S. Murty
Peer-Reviewed Section


The microstructural evolution in the heat-affected zones (HAZs) of boron-added modified 9Cr-1Mo steel (P91B) weldment is distinctly different from that of steel without boron addition (P91). This is accompanied by less reduction in hardness in the inter-critical heat-affected zone (ICHAZ) of the weldment of the boron-containing steel than what is observed in boron-free steel. Though, tensile properties of both the boron-containing steel weldments and boron free-steel weldments do not differ much at room and at high temperatures, there is a significant improvement in the creep strength of the weldment of the boron-containing steel over that of the weldments of boron-free steel. In fact, for creep tests so far completed for weldments of P91B, fracture occurred in the base metal, not in typical Type IV mode (fracture at the ICHAZ or fine grained heat- affected zone) as occurred for the P91 weldment for identical conditions of testing. This improvement is explained based on the role of boron in modifying the HAZ microstructure of the steel.

IIW-Thesaurus keywords

Austenite B additions Creep strength Grain size Heat affected zone Martensite 


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Copyright information

© International Institute of Welding 2012

Authors and Affiliations

  • Chitta R. Das
    • 1
  • Shaju K. Albert
    • 1
  • Arun K. Bhaduri
    • 1
  • Baldev Raj
    • 1
  • Jaganathan Swaminathan
    • 2
  • Budaraju S. Murty
    • 3
  1. 1.Indira Gandhi Centre for Atomic ResearchKalpakkamIndia
  2. 2.National Metallurgical LaboratoryJamshedpurIndia
  3. 3.Indian Institute of Technology MadrasChennaiIndia

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