Effects of elevated temperatures on the mechanical properties of nickel-based alloy clad pipelines girth welds

Fracture capacity of modern pipeline girth welds with 3D surface cracks under extreme operating conditions

“…The analysis provides a better understanding on the amount of conservatism and the suitability of the analytical method for the fracture mechanics assessment of the associated pipeline operating under elevated temperatures or transporting sour media. The fracture capacity of such pipelines under these operating conditions/environments were further assessed based on the tensile stress strain curves as well as the fracture resistance curves obtained from the previous studies [15,16]. Fig.…”

“…When assessing the fracture capacity of the pipeline, the fracture resistance properties of the pipeline girth weld will also be taken into consideration. From the experimental results of the previous study [16], it was demonstrated that when the tests were performed at 180°C, the reduction factor in the fracture resistance was up to 0.6 times for the backing steel (consisting of C-Mn steel) and 0.8 times for the nickel based weld metal/fusion line. Hence, for the same marginal reduction in crack driving force as a result of an increase in operating temperature, it is preferable to use nickel-based welding consumables versus C-Mn steel based ones since the former gives a lower reduction in fracture resistance.…”

“…In previous studies, the authors have investigated the effects of elevated temperatures or sour service environments on the material properties of pipeline girth welds [15,16]. Based on these results, it is demonstrated that the material properties (i.e.…”

“…According to studies performed by Marchi et al [20,21], the CRA layer effectively protects the backing steel from hydrogen damage. In a previous study [16], the authors have established the uniaxial stress strain curves in air environment at elevated temperatures of up to 180°C, and the results were being used for the present analysis.…”

“…5a-c. It should be noted that for the engineering stress strain curves of the various materials used in this study, the elongation to fracture is less than 1 mm/mm [15,16]. For the numerical analysis, the material curves have been defined up to plastic strain of 1 mm/mm as per Eq.…”