| Abstract Scope |
In the natural gas industry, corrosion of steel components due to H2S containing gasses (sour gasses) is a primary concern due to deterioration of equipment, but also because of its toxicity. Martensitic steel components that are exposed to these environments are also often rotating components made of large forgings with complex, machined geometries. In an effort to expedite a return to working conditions, as well as reducing cost, repairing these forgings is preferred over replacing them. When performing weld repairs to these components, distortion from welding and post-weld heat treatments (PWHT) are of primary concern since the components are already in the finished machined condition. In an effort to reduce the heat input to reduce distortion, laser beam welding (LBW) is being investigated. To meet the requirements for weldments and repairs to the National Association of Corrosion Engineers (NACE) standard for these applications, the relative hardness of the material has to be low as this is a simple way to gauge a martensitic alloy’s propensity to corrode. A strategy mimicking temper bead welding is being trialed with pulsed laser welding and continuous wave LBW to employ low heat input strategies while avoiding PWHT. This multilayered technique aims to use precise placement of weld beads to temper the hardened heat affected zone (HAZ) of the martensitic steel. Microstructural and hardness investigations guide welding parameters as well as indicate the success of a multilayered temper bead strategy. |