In-situ loading and PWHT of physically simulated coarse grain heat-affected zone (CGHAZ) to 1010 MPa in a) load cell of dilatometer, fracture topography for b) heating rate of Φ = 33.3 K/h (macro view), c) detailed of intergranular fracture, d) heating rate of Φ = 100 K/h (macro view) and e) corresponding changed topography
Source: BAM, FB9.4 Denis, Czeskleba; BAM FB9.4; Jonathan, Nietzke; BAM FB9.4; Michael Rhode; BAM FB9.4
In the energy industry, components like pressure vessels in petrochemical facilities, and equipment in oil and gas industries often employ the creep-resistant 13CrMoV9-10 steel. With the rise of renewable energy technologies, CrMoV-steels have also found wide application in components of geothermal power plants and concentrated solar power plants, where its creep-resistant properties are highly advantageous. These components are typically joined using submerged arc welding (SAW). However, this type of steel may show stress relief cracks (SRC) if the necessary post-weld heat treatment (PWHT) of the weld joint is not performed correctly. Traditional PWHT parameters, determined by empirical experience and conventional welding experiments, often fail to account for increased residual stresses caused by the surrounding structural rigidity.
This study introduces a novel, efficient, and precise methodology to study the effects of different stress levels and heating rates on the susceptibility of the coarse grain heat affected zone (CGHAZ) to SRC. For this, samples were thermally treated to mimic CGHAZ and then exposed to representative stress levels during PWHT. The ensuing data were mathematically analyzed to identify interdependent effects, providing an integrated measurement of material characteristics like carbide growth.
This new methodology, therefore, offers an improved assessment of the SRC susceptibility of SAW microstructures in creep-resistant steels, an insight that can significantly enhance manufacturing and maintenance protocols in the energy sector, ensuring safety and longevity of crucial components.
Investigation of stress relief crack susceptibility of CrMoV steels coarse grain HAZ via simulation of uniaxial stress conditions during PWHT
Denis Czeskleba, Jonathan Nietzke, Michael Rhode, Thomas Kannengiesser,
published in Welding in the World, pages 1–9 (2023).