Finite element modelling of cobalt base/molybdenum/chromium/silicon coating on pipeline steel substrates and a deepwater rigid jumper

Abstract This work presents the finite element modelling of a deepwater rigid jumper with cobalt-base/chromium/molybdenum/silicon, superalloys internal coating, and a coating-steel pipeline substrate. The objective of the coating is to protect a deepwater jumper steel against the corrosion caused by high content of H2S and CO2 in the oil and gas flow. Experimentally, cobalt-base/chromium/molybdenum/silicon coatings were developed, on substrates of pipeline steel, by a flame thermal spray process, and the properties of the coatings were analyzed. The mechanical properties of the coating were incorporated in the finite element models, and the elastic and plastic stress-strain material response of the jumper and cobalt-base/chromium/molybdenum/silicon coating were incorporated, with the aim to study the structural response of the coating under bending loads. Afterwards, the finite element model of the rigid jumper, with the internal coating, was subjected to hydrostatic and internal pressure representative of a deepwater oil and gas field. The obtained stresses in the coating were below the permissible stress limit, defined by international standards. At the coating-jumper interface, the stresses were also below the permissible stress limit, which means that the coating will remain attached to the jumper under the defined operational conditions. The results also showed that the developed finite element modelling strategy was able to reproduce the true stress-strain curves of the coating and jumper steel materials, which accurately reflected the results of the present finite element modelling.