Overview

Modified 9Cr-1Mo (P91) steel finds its usage in high temperature applications such as in supercritical and ultra super critical power plants. The weldability issues in P91 steel such as formation of delta ferrite in the fusion zone reducing the creep properties, hydrogen induced cracking due to high hardness in as-welded condition and Type-IV cracking in the intercritical zone away from the Heat Affected Zone (HAZ) are expected to be obviated through low heat input welding technique. Autogenous laser welding a low heat input technique when applied on 6 mm thick P91 steel plates using high beam quality (Gaussian,K>0.96) DC035 slab CO2 laser using a focal spot size of 180 µm could successfully address the above stated challenges. 

Key Features

  1. Welds free from both hot and cold cracks and also fusion zone free of delta ferrite and no intercritical soft zone.
  2. The welds have 100 % joint efficiency with failure away from the weld in tensile testing and the welds have sufficient bend ductility.

Potential Applications

  1. Power plant
  2. Nuclear industry

Status

  1. Performance and stability are validated at the coupon level

Intellectual Property Development Index (IPDI)

Level 1 2 3 4 5 6 7 8 9 10
Description Basic concepts and understanding of underlying scientific principles Shortlisting possible applications Research to prove technical feasibility for targeted application Coupon level testing in simulated conditions Check repeatability/consistency Prototype testing in real-life conditions Check repeatability/consistency Reassessing feasibility (IP, competition technology, commercial) Initiate technology transfer Support in stabilizing production
Status

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  1. B. Shanmugarajan, G. Padmanabham, Hemant Kumar, S.K. Albert and A.K.Bhaduri, “Autogenous laser welding investigations on modified 9Cr-1Mo (P91) steels”, Science & Technology of Welding and Joining, Vol.6, No.6, 2011, p528